ChemWiki - User contributions [en]

Rep:Mod:MaxBridge

2017-03-11T18:34:52Z

Mhb314: /* Conclusion */

== '''Introduction''' ==

A potential energy surface (PES) is used to show the energy of a system as a function pof the positions of the atoms in that system.
A PES can be used to determine whether a transition state occurs during a reaction, in which a species is made that is different to the reactants and the products. When evaluating the stationary points on a PES, ie when the gradient is zero, it is found that the minima points are where the reactants and products are located and the maxima occurs when a transition state occurs. To confirm where the minima and maxima are the second derivative is taken and are found to be postive and negative respectively. Furthermore through using gaussian it can be shown that a transition sate will a negative frequency and the reactants and products will not.

During this report there will be three different exercises explored using Gaussian in which the reactants, products and transition states were all optimised at the PM6 level along with frequency calculations also performed. For exercise 2 the products were also ran at the B3LYP/6-31(d) level. An IRC calculation was ran for every reaction in order to show the reaction coordinate.

== Exercise 1: Reaction of Butadiene with Ethylene ==

[[File:Reaction scheme.jpg]]

This reaction has been analyzed by optimizing the reactants and transition state using Gaussian at the PM6 level. The presence of a transition state was confirmed by running a frequency calculation at the PM6 level of the transition state and a negative frequency of -948.80 being shown.

==='''Molecular Orbital Analysis'''===

[[File:MaxbMODiagram.jpg]]

The molecular orbital diagram shows the HOMO and LUMO of both reactants and the transition state.

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO of Butadiene and Ethylene
|-
| style="text-align: center;"|HOMO of Butadiene
| style="text-align: center;"|LUMO of Butadiene
| style="text-align: center;"|HOMO of Ethylene
| style="text-align: center;"|LUMO of Ethylene
|-
| align="center"|[[File:MaxbButadieneHOMO.jpg|250px]]
| align="center"|[[File:MaxbButadieneLUMO.jpg|250px]]
| align="center"|[[File:MaxbEtheneHOMO.jpg|250px]]
| align="center"|[[File:MaxBEtheneLUMO.jpg|250px]]
|}
[[Media:ETHENEOPTMAXB.LOG]]
[[Media:BUTADIENEOPTMAXB.LOG]]
 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ Molecular Orbitals of the Transition State
|-
| style="text-align: center;"|MO 16 of TS
| style="text-align: center;"|HOMO of TS
| style="text-align: center;"|LUMO of TS
| style="text-align: center;"|MO 19 of TS
|-
| align="center"|[[File:MaxbTSMO16.jpg|250px]]
| align="center"|[[File:MaxbTSHOMO.jpg|250px]]
| align="center"|[[File:MaxbTSLUMO.jpg|250px]]
| align="center"|[[File:MaxbTSMO19.jpg|250px]]
|}
[[Media:BUTAANDETHANETS.LOG]]

 

The HOMO of the ethylene and the LUMO of the butadiene are both of gerade symmetry so they interact to produce molecular orbitals shown above. The HOMO of the butadiene and the LUMO of the ethylene are both of ungerade symmetry so they interact to give molecular orbital shown above. This follows a typical Diels-Alder reaction as the HOMO of butadiene is of higher energy than the HOMO of the ethylene.

==='''Bond Length Analysis'''===

{| class="wikitable" style="margin: 1em auto 1em auto;"
! rowspan="2" style="text-align: center;" | Carbon Bonds
! colspan="3" style="text-align: center;" | Bond Length (Å)
|-
| style="text-align: center;" | Reactants
| style="text-align: center;" | Transition State
| style="text-align: center;" | Product
|-
| C1-C2
| style="text-align: center;" | 1.33528
| style="text-align: center;" | 1.37980
| style="text-align: center;" | 1.50090
|-
| C2-C3
| style="text-align: center;" | 1.46837
| style="text-align: center;" | 1.41112
| style="text-align: center;" | 1.33784
|-
| C3-C4
| style="text-align: center;" | 1.33528
| style="text-align: center;" | 1.37979
| style="text-align: center;" | 1.50090
|-
| C4-C5
| style="text-align: center;" | n/a
| style="text-align: center;" | 2.11464
| style="text-align: center;" | 1.54040
|-
| C5-C6
| style="text-align: center;" | 1.32741
| style="text-align: center;" | 1.38177
| style="text-align: center;" | 1.54091
|-
| C6-C1
| style="text-align: center;" | n/a
| style="text-align: center;" | 2.11482
| style="text-align: center;" | 1.54040
|}

 
There is an increase in bond length between C1-C2, C3-C4 and C5-C6 going from reactants to products. This is due to C1, C4, C5 and C6 all going from being sp2 hybridized to sp3 and as a result changing C1-C2, C3-C4 and C5-C6 from double bonds to single bonds. C2 and C3 remain sp2 but the bond between goes from single to double, hence the shortening in length.
The literature value for between an sp3 carbon and an sp2 carbon in cyclohexene is 1.506 Å [1] , between two sp3 carbons it is 1.541 and between two sp2 carbons it is 1.326. these are very similar values to the ones given above and show the accuracy of Gaussian.
The van der vaals radius of carbon is 1.7 Å [2] according to Pauling (1939). The distance between C4-C5 and C6-C1 is 2.11482 which is much less than double 1.7 meaning the interactions between them are much stronger than VDVs forces.

==='''Transition State'''===
 

[[File:ButaEthaneTSMB.gif|center]]
[[MediaːBUTAANDETHANETS.LOG]]

 

The above vibration shows that the new C-C bonds form synchronously as the C-C bond of the butadiene is compressed whilst the terminal carbon atoms of each reactant move closer together simultaneously.

==='''Reaction Path'''===

==Exercise 2ː Reaction of Cyclohexadiene and 1,3-Dioxole==

 

[[File:MaxBScheme2.jpg]]
 

The reactants, transition states and the exo- and endo- adducts of the product were optimized to the B3LYP/6-31G(d) level on Gaussian.

 

==='''Molecular Orbital Analysis'''===

 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO of Cyclohexadiene and 1,3-Dioxole
|-
| style="text-align: center;"|HOMO of Cyclohexadiene
| style="text-align: center;"|LUMO of Cyclohexadiene
| style="text-align: center;"|HOMO of 1,3-Dioxole
| style="text-align: center;"|LUMO of 1,3-Dioxole
|-
| align="center"|[[File:MaxbButadieneHOMO.jpg|250px]]
| align="center"|[[File:MaxbHEXALUMO.jpg|250px]]
| align="center"|[[File:MaxbOXYHOMO.jpg|250px]]
| align="center"|[[File:MaxbOXYLUMO.jpg|250px]]
|}
[[Media:CYCLOOXYGEN2.LOG]]
[[Media:CYCLOHEXADIENEDFTMAXB.LOG]]

 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO Endo- and Exo- Trasition States
|-
| style="text-align: center;"|HOMO of EXO-
| style="text-align: center;"|LUMO of EXO-
| style="text-align: center;"|HOMO of ENDO-
| style="text-align: center;"|LUMO of ENDO-
|-
| align="center"|[[File:MaxbEXOHOMO.jpg|250px]]
| align="center"|[[File:MaxBEXOLUMO.jpg|250px]]
| align="center"|[[File:MaxbENDOHOMO.jpg|250px]]
| align="center"|[[File:MaxbENDOLUMO.jpg|250px]]
|}

[[Media:REACTANTS TS B3LPY.LOG]]
[[Media:REACTANTS ENDO TS B3LPY.LOG]]

 

This reaction is between an electron rich dienophile (Cyclohexadiene) and an electron-poor diene (1,3-Dioxole) meaning that an inverse electron demand Diels-Alder reaction occurs. The main difference between the molecular orbitals in an inverse and a standard Diels-Alder reaction is that in an inverse reaction the HOMO of the diene is lower in energy than the LUMO of the Dienophile.

==='''Thermochemistry'''===
 

{| class="wikitable" style="margin: 1em auto 1em auto;"
! style="font-weight: bold;" |
! style="font-weight: bold;" | Reactants
! style="font-weight: bold;" | Transition State
! style="font-weight: bold;" | Product
! style="font-weight: bold;" | Ea
! style="font-weight: bold;" | ΔGr
|-
| Exo
| -500.389165
| -500.329168
| -500.417323
| 0.060
| 0.028
|-
| Endo
| -500.389165
| -500.332111
| -500.418691
| 0.057
| 0.030
|}

 

The endo product is shown here to have both a lower activation energy and a large change in gibbs energy meaning that it is both the kinetic and thermodynamic product.
This is because in the endo product the p-orbitals on the oxygen of the 1,3-dioxole are interacting with the pi orbitals of the new carbon-carbon double bond resulting in a stabilised transition state. Furthermore there is steric hinderance in the exo transition state between the two oxygen atoms and ethane bridge.

==Exercise 3: Diels-Alder vs Cheletropic==

 

[[File:MaxbReactionScheme3.jpg|centre]]

 

===Diels-Alder: EXO===
Reaction Coordinate:

 

[[File:MaxbEXOIRC.gif]]

====IRC Path====

[[File:Total Energy along IRC EXO.pdf]]
[[Media:REACTANTSEXOIRC.LOG]]
====Energy Profile for Exo Product====

[[File:MaxbEXO.jpg]]

 

===Diels-Alder: Endo===

[[File:MaxbENDOIRC.gif]]

====IRC Path====

[[File:Total Energy along IRC ENDO.pdf]]
[[Media:REACTANTSENDOIRC.LOG]]

The IRC shown here is in reverse resulting in it going from products to reactants.

====Energy Profile for Endo Product====

[[File:MaxbENDO.jpg]]

 

The IRCs of both the endo and exo reactions show the formation of a new six membered ring. It can be seen in both reaction paths that there is a delocalistion of electrons throughout the xylylene due to it being highly unstable. The reaction paths show that the exo- product is favored kinetically and thermodynamically due to it having a lower activation energy and large change in gibbs energy.

 

===Cheletropic reaction===

[[File:MaxbCHELOIRC.gif]]

====IRC Path====
[[File:Total Energy along IRC CHELO.pdf]]

====Energy Profile for Chelotropic reaction====

[[File:MaxbCHELO.jpg]]

 

The chelotropic reaction shows a higher activation energy in comparison to the diels-alder reaction, this is down to a five membered ring forming which is more strained than the 6 membered ring formed in the diels-alder reaction. The chelotropic reaction has a much higher change in gibbs energy than the diels-alder reaction meaning that the chelotropic product would form under thermodynamic control and the diels-alder under kinetic control.

==Conclusion==

In all three exercises the reactants, products and transition states were successfully optimized under the PM6, with the endo- and exo- reaction paths also being successfully optimized to the B3LYP/6-31G(d) level. This resulted in successful anaylsis of the HOMOs and LUMOs of the reactants and transition states for reactions in the first two exercises. Furthermore it lead to thermochemical data about the reaction paths being analysed for the reaction in exercises 2 and 3 which meant that the kinetic and thermodynamic products could be subsequently confirmed.

==References==
[1] F. H. Allen, O. Kennard, D. G. Watson, L. Brammer and A. G. Orpen, 1987, 1–19.
[2] S. S. Batsanov, 2001, 37, 871–885.

Rep:Mod:MaxBridge

2017-03-11T18:33:00Z

Mhb314: /* Exercise 1: Reaction of Butadiene with Ethylene */

Rep:Mod:MaxBridge

2017-03-11T18:26:11Z

Mhb314: /* Exercise 3: Diels-Alder vs Cheletropic */

== '''Introduction''' ==

A potential energy surface (PES) is used to show the energy of a system as a function pof the positions of the atoms in that system.
A PES can be used to determine whether a transition state occurs during a reaction, in which a species is made that is different to the reactants and the products. When evaluating the stationary points on a PES, ie when the gradient is zero, it is found that the minima points are where the reactants and products are located and the maxima occurs when a transition state occurs. To confirm where the minima and maxima are the second derivative is taken and are found to be postive and negative respectively. Furthermore through using gaussian it can be shown that a transition sate will a negative frequency and the reactants and products will not.

During this report there will be three different exercises explored using Gaussian in which the reactants, products and transition states were all optimised at the PM6 level along with frequency calculations also performed. For exercise 2 the products were also ran at the B3LYP/6-31(d) level. An IRC calculation was ran for every reaction in order to show the reaction coordinate.

== Exercise 1: Reaction of Butadiene with Ethylene ==

[[File:Reaction scheme.jpg]]

This reaction has been analyzed by optimizing the reactants and transition state using Gaussian at the PM6 level. The presence of a transition state was confirmed by running a frequency calculation at the PM6 level of the transition state and a negative frequency of -948.80 being shown.

==='''Molecular Orbital Analysis'''===

[[File:MaxbMODiagram.jpg]]

The molecular orbital diagram shows the HOMO and LUMO of both reactants and the transition state.

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO of Butadiene and Ethylene
|-
| style="text-align: center;"|HOMO of Butadiene
| style="text-align: center;"|LUMO of Butadiene
| style="text-align: center;"|HOMO of Ethylene
| style="text-align: center;"|LUMO of Ethylene
|-
| align="center"|[[File:MaxbButadieneHOMO.jpg|250px]]
| align="center"|[[File:MaxbButadieneLUMO.jpg|250px]]
| align="center"|[[File:MaxbEtheneHOMO.jpg|250px]]
| align="center"|[[File:MaxBEtheneLUMO.jpg|250px]]
|}
[[Media:ETHENEOPTMAXB.LOG]]
[[Media:BUTADIENEOPTMAXB.LOG]]
 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ Molecular Orbitals of the Transition State
|-
| style="text-align: center;"|MO 16 of TS
| style="text-align: center;"|HOMO of TS
| style="text-align: center;"|LUMO of TS
| style="text-align: center;"|MO 19 of TS
|-
| align="center"|[[File:MaxbTSMO16.jpg|250px]]
| align="center"|[[File:MaxbTSHOMO.jpg|250px]]
| align="center"|[[File:MaxbTSLUMO.jpg|250px]]
| align="center"|[[File:MaxbTSMO19.jpg|250px]]
|}
[[Media:BUTAANDETHANETS.LOG]]

 

The HOMO of the ethylene and the LUMO of the butadiene are both of gerade symmetry so they interact to produce molecular orbitals shown above. The HOMO of the butadiene and the LUMO of the ethylene are both of ungerade symmetry so they interact to give molecular orbital shown above. This follows a typical Diels-Alder reaction as the HOMO of butadiene is of higher energy than the HOMO of the ethylene.

===Bond Length Analysis===

{| class="wikitable" style="margin: 1em auto 1em auto;"
! rowspan="2" style="text-align: center;" | Carbon Bonds
! colspan="3" style="text-align: center;" | Bond Length (Å)
|-
| style="text-align: center;" | Reactants
| style="text-align: center;" | Transition State
| style="text-align: center;" | Product
|-
| C1-C2
| style="text-align: center;" | 1.33528
| style="text-align: center;" | 1.37980
| style="text-align: center;" | 1.50090
|-
| C2-C3
| style="text-align: center;" | 1.46837
| style="text-align: center;" | 1.41112
| style="text-align: center;" | 1.33784
|-
| C3-C4
| style="text-align: center;" | 1.33528
| style="text-align: center;" | 1.37979
| style="text-align: center;" | 1.50090
|-
| C4-C5
| style="text-align: center;" | n/a
| style="text-align: center;" | 2.11464
| style="text-align: center;" | 1.54040
|-
| C5-C6
| style="text-align: center;" | 1.32741
| style="text-align: center;" | 1.38177
| style="text-align: center;" | 1.54091
|-
| C6-C1
| style="text-align: center;" | n/a
| style="text-align: center;" | 2.11482
| style="text-align: center;" | 1.54040
|}

==='''Transition State'''===
 

[[File:ButaEthaneTSMB.gif|center]]
[[MediaːBUTAANDETHANETS.LOG]]

 

The above vibration shows that the new C-C bonds form synchronously as the C-C bond of the butadiene is compressed whilst the terminal carbon atoms of each reactant move closer together simultaneously.

==='''Reaction Path'''===

==Exercise 2ː Reaction of Cyclohexadiene and 1,3-Dioxole==

 

[[File:MaxBScheme2.jpg]]
 

The reactants, transition states and the exo- and endo- adducts of the product were optimized to the B3LYP/6-31G(d) level on Gaussian.

 

==='''Molecular Orbital Analysis'''===

 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO of Cyclohexadiene and 1,3-Dioxole
|-
| style="text-align: center;"|HOMO of Cyclohexadiene
| style="text-align: center;"|LUMO of Cyclohexadiene
| style="text-align: center;"|HOMO of 1,3-Dioxole
| style="text-align: center;"|LUMO of 1,3-Dioxole
|-
| align="center"|[[File:MaxbButadieneHOMO.jpg|250px]]
| align="center"|[[File:MaxbHEXALUMO.jpg|250px]]
| align="center"|[[File:MaxbOXYHOMO.jpg|250px]]
| align="center"|[[File:MaxbOXYLUMO.jpg|250px]]
|}
[[Media:CYCLOOXYGEN2.LOG]]
[[Media:CYCLOHEXADIENEDFTMAXB.LOG]]

 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO Endo- and Exo- Trasition States
|-
| style="text-align: center;"|HOMO of EXO-
| style="text-align: center;"|LUMO of EXO-
| style="text-align: center;"|HOMO of ENDO-
| style="text-align: center;"|LUMO of ENDO-
|-
| align="center"|[[File:MaxbEXOHOMO.jpg|250px]]
| align="center"|[[File:MaxBEXOLUMO.jpg|250px]]
| align="center"|[[File:MaxbENDOHOMO.jpg|250px]]
| align="center"|[[File:MaxbENDOLUMO.jpg|250px]]
|}

[[Media:REACTANTS TS B3LPY.LOG]]
[[Media:REACTANTS ENDO TS B3LPY.LOG]]

 

This reaction is between an electron rich dienophile (Cyclohexadiene) and an electron-poor diene (1,3-Dioxole) meaning that an inverse electron demand Diels-Alder reaction occurs. The main difference between the molecular orbitals in an inverse and a standard Diels-Alder reaction is that in an inverse reaction the HOMO of the diene is lower in energy than the LUMO of the Dienophile.

==='''Thermochemistry'''===
 

{| class="wikitable" style="margin: 1em auto 1em auto;"
! style="font-weight: bold;" |
! style="font-weight: bold;" | Reactants
! style="font-weight: bold;" | Transition State
! style="font-weight: bold;" | Product
! style="font-weight: bold;" | Ea
! style="font-weight: bold;" | ΔGr
|-
| Exo
| -500.389165
| -500.329168
| -500.417323
| 0.060
| 0.028
|-
| Endo
| -500.389165
| -500.332111
| -500.418691
| 0.057
| 0.030
|}

 

The endo product is shown here to have both a lower activation energy and a large change in gibbs energy meaning that it is both the kinetic and thermodynamic product.
This is because in the endo product the p-orbitals on the oxygen of the 1,3-dioxole are interacting with the pi orbitals of the new carbon-carbon double bond resulting in a stabilised transition state. Furthermore there is steric hinderance in the exo transition state between the two oxygen atoms and ethane bridge.

==Exercise 3: Diels-Alder vs Cheletropic==

 

[[File:MaxbReactionScheme3.jpg|centre]]

 

===Diels-Alder: EXO===
Reaction Coordinate:

 

[[File:MaxbEXOIRC.gif]]

====IRC Path====

[[File:Total Energy along IRC EXO.pdf]]
[[Media:REACTANTSEXOIRC.LOG]]
====Energy Profile for Exo Product====

[[File:MaxbEXO.jpg]]

 

===Diels-Alder: Endo===

[[File:MaxbENDOIRC.gif]]

====IRC Path====

[[File:Total Energy along IRC ENDO.pdf]]
[[Media:REACTANTSENDOIRC.LOG]]

The IRC shown here is in reverse resulting in it going from products to reactants.

====Energy Profile for Endo Product====

[[File:MaxbENDO.jpg]]

 

The IRCs of both the endo and exo reactions show the formation of a new six membered ring. It can be seen in both reaction paths that there is a delocalistion of electrons throughout the xylylene due to it being highly unstable. The reaction paths show that the exo- product is favored kinetically and thermodynamically due to it having a lower activation energy and large change in gibbs energy.

 

===Cheletropic reaction===

[[File:MaxbCHELOIRC.gif]]

====IRC Path====
[[File:Total Energy along IRC CHELO.pdf]]

====Energy Profile for Chelotropic reaction====

[[File:MaxbCHELO.jpg]]

 

The chelotropic reaction shows a higher activation energy in comparison to the diels-alder reaction, this is down to a five membered ring forming which is more strained than the 6 membered ring formed in the diels-alder reaction. The chelotropic reaction has a much higher change in gibbs energy than the diels-alder reaction meaning that the chelotropic product would form under thermodynamic control and the diels-alder under kinetic control.

==Conclusion==

In all three exercises the reactants, products and transition states were successfully optimized under the PM6, with the endo- and exo- reaction paths also being successfully optimized to the B3LYP/6-31G(d) level. This resulted in successful anaylsis of the HOMOs and LUMOs of the reactants and transition states for reactions in the first two exercises. Furthermore it lead to thermochemical data about the reaction paths being analysed for the reaction in exercises 2 and 3 which meant that the kinetic and thermodynamic products could be subsequently confirmed.

Rep:Mod:MaxBridge

2017-03-11T18:20:40Z

Mhb314: /* Energy Profile for Chelotropic reaction */

== '''Introduction''' ==

A potential energy surface (PES) is used to show the energy of a system as a function pof the positions of the atoms in that system.
A PES can be used to determine whether a transition state occurs during a reaction, in which a species is made that is different to the reactants and the products. When evaluating the stationary points on a PES, ie when the gradient is zero, it is found that the minima points are where the reactants and products are located and the maxima occurs when a transition state occurs. To confirm where the minima and maxima are the second derivative is taken and are found to be postive and negative respectively. Furthermore through using gaussian it can be shown that a transition sate will a negative frequency and the reactants and products will not.

During this report there will be three different exercises explored using Gaussian in which the reactants, products and transition states were all optimised at the PM6 level along with frequency calculations also performed. For exercise 2 the products were also ran at the B3LYP/6-31(d) level. An IRC calculation was ran for every reaction in order to show the reaction coordinate.

== Exercise 1: Reaction of Butadiene with Ethylene ==

[[File:Reaction scheme.jpg]]

This reaction has been analyzed by optimizing the reactants and transition state using Gaussian at the PM6 level. The presence of a transition state was confirmed by running a frequency calculation at the PM6 level of the transition state and a negative frequency of -948.80 being shown.

==='''Molecular Orbital Analysis'''===

[[File:MaxbMODiagram.jpg]]

The molecular orbital diagram shows the HOMO and LUMO of both reactants and the transition state.

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO of Butadiene and Ethylene
|-
| style="text-align: center;"|HOMO of Butadiene
| style="text-align: center;"|LUMO of Butadiene
| style="text-align: center;"|HOMO of Ethylene
| style="text-align: center;"|LUMO of Ethylene
|-
| align="center"|[[File:MaxbButadieneHOMO.jpg|250px]]
| align="center"|[[File:MaxbButadieneLUMO.jpg|250px]]
| align="center"|[[File:MaxbEtheneHOMO.jpg|250px]]
| align="center"|[[File:MaxBEtheneLUMO.jpg|250px]]
|}
[[Media:ETHENEOPTMAXB.LOG]]
[[Media:BUTADIENEOPTMAXB.LOG]]
 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ Molecular Orbitals of the Transition State
|-
| style="text-align: center;"|MO 16 of TS
| style="text-align: center;"|HOMO of TS
| style="text-align: center;"|LUMO of TS
| style="text-align: center;"|MO 19 of TS
|-
| align="center"|[[File:MaxbTSMO16.jpg|250px]]
| align="center"|[[File:MaxbTSHOMO.jpg|250px]]
| align="center"|[[File:MaxbTSLUMO.jpg|250px]]
| align="center"|[[File:MaxbTSMO19.jpg|250px]]
|}
[[Media:BUTAANDETHANETS.LOG]]

 

The HOMO of the ethylene and the LUMO of the butadiene are both of gerade symmetry so they interact to produce molecular orbitals shown above. The HOMO of the butadiene and the LUMO of the ethylene are both of ungerade symmetry so they interact to give molecular orbital shown above. This follows a typical Diels-Alder reaction as the HOMO of butadiene is of higher energy than the HOMO of the ethylene.

===Bond Length Analysis===

{| class="wikitable" style="margin: 1em auto 1em auto;"
! rowspan="2" style="text-align: center;" | Carbon Bonds
! colspan="3" style="text-align: center;" | Bond Length (Å)
|-
| style="text-align: center;" | Reactants
| style="text-align: center;" | Transition State
| style="text-align: center;" | Product
|-
| C1-C2
| style="text-align: center;" | 1.33528
| style="text-align: center;" | 1.37980
| style="text-align: center;" | 1.50090
|-
| C2-C3
| style="text-align: center;" | 1.46837
| style="text-align: center;" | 1.41112
| style="text-align: center;" | 1.33784
|-
| C3-C4
| style="text-align: center;" | 1.33528
| style="text-align: center;" | 1.37979
| style="text-align: center;" | 1.50090
|-
| C4-C5
| style="text-align: center;" | n/a
| style="text-align: center;" | 2.11464
| style="text-align: center;" | 1.54040
|-
| C5-C6
| style="text-align: center;" | 1.32741
| style="text-align: center;" | 1.38177
| style="text-align: center;" | 1.54091
|-
| C6-C1
| style="text-align: center;" | n/a
| style="text-align: center;" | 2.11482
| style="text-align: center;" | 1.54040
|}

==='''Transition State'''===
 

[[File:ButaEthaneTSMB.gif|center]]
[[MediaːBUTAANDETHANETS.LOG]]

 

The above vibration shows that the new C-C bonds form synchronously as the C-C bond of the butadiene is compressed whilst the terminal carbon atoms of each reactant move closer together simultaneously.

==='''Reaction Path'''===

==Exercise 2ː Reaction of Cyclohexadiene and 1,3-Dioxole==

 

[[File:MaxBScheme2.jpg]]
 

The reactants, transition states and the exo- and endo- adducts of the product were optimized to the B3LYP/6-31G(d) level on Gaussian.

 

==='''Molecular Orbital Analysis'''===

 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO of Cyclohexadiene and 1,3-Dioxole
|-
| style="text-align: center;"|HOMO of Cyclohexadiene
| style="text-align: center;"|LUMO of Cyclohexadiene
| style="text-align: center;"|HOMO of 1,3-Dioxole
| style="text-align: center;"|LUMO of 1,3-Dioxole
|-
| align="center"|[[File:MaxbButadieneHOMO.jpg|250px]]
| align="center"|[[File:MaxbHEXALUMO.jpg|250px]]
| align="center"|[[File:MaxbOXYHOMO.jpg|250px]]
| align="center"|[[File:MaxbOXYLUMO.jpg|250px]]
|}
[[Media:CYCLOOXYGEN2.LOG]]
[[Media:CYCLOHEXADIENEDFTMAXB.LOG]]

 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO Endo- and Exo- Trasition States
|-
| style="text-align: center;"|HOMO of EXO-
| style="text-align: center;"|LUMO of EXO-
| style="text-align: center;"|HOMO of ENDO-
| style="text-align: center;"|LUMO of ENDO-
|-
| align="center"|[[File:MaxbEXOHOMO.jpg|250px]]
| align="center"|[[File:MaxBEXOLUMO.jpg|250px]]
| align="center"|[[File:MaxbENDOHOMO.jpg|250px]]
| align="center"|[[File:MaxbENDOLUMO.jpg|250px]]
|}

[[Media:REACTANTS TS B3LPY.LOG]]
[[Media:REACTANTS ENDO TS B3LPY.LOG]]

 

This reaction is between an electron rich dienophile (Cyclohexadiene) and an electron-poor diene (1,3-Dioxole) meaning that an inverse electron demand Diels-Alder reaction occurs. The main difference between the molecular orbitals in an inverse and a standard Diels-Alder reaction is that in an inverse reaction the HOMO of the diene is lower in energy than the LUMO of the Dienophile.

==='''Thermochemistry'''===
 

{| class="wikitable" style="margin: 1em auto 1em auto;"
! style="font-weight: bold;" |
! style="font-weight: bold;" | Reactants
! style="font-weight: bold;" | Transition State
! style="font-weight: bold;" | Product
! style="font-weight: bold;" | Ea
! style="font-weight: bold;" | ΔGr
|-
| Exo
| -500.389165
| -500.329168
| -500.417323
| 0.060
| 0.028
|-
| Endo
| -500.389165
| -500.332111
| -500.418691
| 0.057
| 0.030
|}

 

The endo product is shown here to have both a lower activation energy and a large change in gibbs energy meaning that it is both the kinetic and thermodynamic product.
This is because in the endo product the p-orbitals on the oxygen of the 1,3-dioxole are interacting with the pi orbitals of the new carbon-carbon double bond resulting in a stabilised transition state. Furthermore there is steric hinderance in the exo transition state between the two oxygen atoms and ethane bridge.

==Exercise 3: Diels-Alder vs Cheletropic==

 

[[File:MaxbReactionScheme3.jpg|centre]]

 

===Diels-Alder: EXO===
Reaction Coordinate:

 

[[File:MaxbEXOIRC.gif]]

====IRC Path====

[[File:Total Energy along IRC EXO.pdf]]
[[Media:REACTANTSEXOIRC.LOG]]
====Energy Profile for Exo Product====

[[File:MaxbEXO.jpg]]

 

===Diels-Alder: Endo===

[[File:MaxbENDOIRC.gif]]

====IRC Path====

[[File:Total Energy along IRC ENDO.pdf]]
[[Media:REACTANTSENDOIRC.LOG]]

The IRC shown here is in reverse resulting in it going from products to reactants.

====Energy Profile for Endo Product====

[[File:MaxbENDO.jpg]]

 

The IRCs of both the endo and exo reactions show the formation of a new six membered ring. It can be seen in both reaction paths that there is a delocalistion of electrons throughout the xylylene due to it being highly unstable. The reaction paths show that the exo- product is favored kinetically and thermodynamically due to it having a lower activation energy and large change in gibbs energy.

 

===Cheletropic reaction===

[[File:MaxbCHELOIRC.gif]]

====IRC Path====
[[File:Total Energy along IRC CHELO.pdf]]

====Energy Profile for Chelotropic reaction====

[[File:MaxbCHELO.jpg]]

 

The chelotropic reaction shows a higher activation energy in comparison to the diels-alder reaction, this is down to a five membered ring forming which is more strained than the 6 membered ring formed in the diels-alder reaction. The chelotropic reaction has a much higher change in gibbs energy than the diels-alder reaction meaning that the chelotropic product would form under thermodynamic control and the diels-alder under kinetic control.

==

Rep:Mod:MaxBridge

2017-03-11T18:20:08Z

Mhb314: /* Exercise 3: Diels-Alder vs Cheletropic */

== '''Introduction''' ==

A potential energy surface (PES) is used to show the energy of a system as a function pof the positions of the atoms in that system.
A PES can be used to determine whether a transition state occurs during a reaction, in which a species is made that is different to the reactants and the products. When evaluating the stationary points on a PES, ie when the gradient is zero, it is found that the minima points are where the reactants and products are located and the maxima occurs when a transition state occurs. To confirm where the minima and maxima are the second derivative is taken and are found to be postive and negative respectively. Furthermore through using gaussian it can be shown that a transition sate will a negative frequency and the reactants and products will not.

During this report there will be three different exercises explored using Gaussian in which the reactants, products and transition states were all optimised at the PM6 level along with frequency calculations also performed. For exercise 2 the products were also ran at the B3LYP/6-31(d) level. An IRC calculation was ran for every reaction in order to show the reaction coordinate.

== Exercise 1: Reaction of Butadiene with Ethylene ==

[[File:Reaction scheme.jpg]]

This reaction has been analyzed by optimizing the reactants and transition state using Gaussian at the PM6 level. The presence of a transition state was confirmed by running a frequency calculation at the PM6 level of the transition state and a negative frequency of -948.80 being shown.

==='''Molecular Orbital Analysis'''===

[[File:MaxbMODiagram.jpg]]

The molecular orbital diagram shows the HOMO and LUMO of both reactants and the transition state.

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO of Butadiene and Ethylene
|-
| style="text-align: center;"|HOMO of Butadiene
| style="text-align: center;"|LUMO of Butadiene
| style="text-align: center;"|HOMO of Ethylene
| style="text-align: center;"|LUMO of Ethylene
|-
| align="center"|[[File:MaxbButadieneHOMO.jpg|250px]]
| align="center"|[[File:MaxbButadieneLUMO.jpg|250px]]
| align="center"|[[File:MaxbEtheneHOMO.jpg|250px]]
| align="center"|[[File:MaxBEtheneLUMO.jpg|250px]]
|}
[[Media:ETHENEOPTMAXB.LOG]]
[[Media:BUTADIENEOPTMAXB.LOG]]
 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ Molecular Orbitals of the Transition State
|-
| style="text-align: center;"|MO 16 of TS
| style="text-align: center;"|HOMO of TS
| style="text-align: center;"|LUMO of TS
| style="text-align: center;"|MO 19 of TS
|-
| align="center"|[[File:MaxbTSMO16.jpg|250px]]
| align="center"|[[File:MaxbTSHOMO.jpg|250px]]
| align="center"|[[File:MaxbTSLUMO.jpg|250px]]
| align="center"|[[File:MaxbTSMO19.jpg|250px]]
|}
[[Media:BUTAANDETHANETS.LOG]]

 

The HOMO of the ethylene and the LUMO of the butadiene are both of gerade symmetry so they interact to produce molecular orbitals shown above. The HOMO of the butadiene and the LUMO of the ethylene are both of ungerade symmetry so they interact to give molecular orbital shown above. This follows a typical Diels-Alder reaction as the HOMO of butadiene is of higher energy than the HOMO of the ethylene.

===Bond Length Analysis===

{| class="wikitable" style="margin: 1em auto 1em auto;"
! rowspan="2" style="text-align: center;" | Carbon Bonds
! colspan="3" style="text-align: center;" | Bond Length (Å)
|-
| style="text-align: center;" | Reactants
| style="text-align: center;" | Transition State
| style="text-align: center;" | Product
|-
| C1-C2
| style="text-align: center;" | 1.33528
| style="text-align: center;" | 1.37980
| style="text-align: center;" | 1.50090
|-
| C2-C3
| style="text-align: center;" | 1.46837
| style="text-align: center;" | 1.41112
| style="text-align: center;" | 1.33784
|-
| C3-C4
| style="text-align: center;" | 1.33528
| style="text-align: center;" | 1.37979
| style="text-align: center;" | 1.50090
|-
| C4-C5
| style="text-align: center;" | n/a
| style="text-align: center;" | 2.11464
| style="text-align: center;" | 1.54040
|-
| C5-C6
| style="text-align: center;" | 1.32741
| style="text-align: center;" | 1.38177
| style="text-align: center;" | 1.54091
|-
| C6-C1
| style="text-align: center;" | n/a
| style="text-align: center;" | 2.11482
| style="text-align: center;" | 1.54040
|}

==='''Transition State'''===
 

[[File:ButaEthaneTSMB.gif|center]]
[[MediaːBUTAANDETHANETS.LOG]]

 

The above vibration shows that the new C-C bonds form synchronously as the C-C bond of the butadiene is compressed whilst the terminal carbon atoms of each reactant move closer together simultaneously.

==='''Reaction Path'''===

==Exercise 2ː Reaction of Cyclohexadiene and 1,3-Dioxole==

 

[[File:MaxBScheme2.jpg]]
 

The reactants, transition states and the exo- and endo- adducts of the product were optimized to the B3LYP/6-31G(d) level on Gaussian.

 

==='''Molecular Orbital Analysis'''===

 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO of Cyclohexadiene and 1,3-Dioxole
|-
| style="text-align: center;"|HOMO of Cyclohexadiene
| style="text-align: center;"|LUMO of Cyclohexadiene
| style="text-align: center;"|HOMO of 1,3-Dioxole
| style="text-align: center;"|LUMO of 1,3-Dioxole
|-
| align="center"|[[File:MaxbButadieneHOMO.jpg|250px]]
| align="center"|[[File:MaxbHEXALUMO.jpg|250px]]
| align="center"|[[File:MaxbOXYHOMO.jpg|250px]]
| align="center"|[[File:MaxbOXYLUMO.jpg|250px]]
|}
[[Media:CYCLOOXYGEN2.LOG]]
[[Media:CYCLOHEXADIENEDFTMAXB.LOG]]

 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO Endo- and Exo- Trasition States
|-
| style="text-align: center;"|HOMO of EXO-
| style="text-align: center;"|LUMO of EXO-
| style="text-align: center;"|HOMO of ENDO-
| style="text-align: center;"|LUMO of ENDO-
|-
| align="center"|[[File:MaxbEXOHOMO.jpg|250px]]
| align="center"|[[File:MaxBEXOLUMO.jpg|250px]]
| align="center"|[[File:MaxbENDOHOMO.jpg|250px]]
| align="center"|[[File:MaxbENDOLUMO.jpg|250px]]
|}

[[Media:REACTANTS TS B3LPY.LOG]]
[[Media:REACTANTS ENDO TS B3LPY.LOG]]

 

This reaction is between an electron rich dienophile (Cyclohexadiene) and an electron-poor diene (1,3-Dioxole) meaning that an inverse electron demand Diels-Alder reaction occurs. The main difference between the molecular orbitals in an inverse and a standard Diels-Alder reaction is that in an inverse reaction the HOMO of the diene is lower in energy than the LUMO of the Dienophile.

==='''Thermochemistry'''===
 

{| class="wikitable" style="margin: 1em auto 1em auto;"
! style="font-weight: bold;" |
! style="font-weight: bold;" | Reactants
! style="font-weight: bold;" | Transition State
! style="font-weight: bold;" | Product
! style="font-weight: bold;" | Ea
! style="font-weight: bold;" | ΔGr
|-
| Exo
| -500.389165
| -500.329168
| -500.417323
| 0.060
| 0.028
|-
| Endo
| -500.389165
| -500.332111
| -500.418691
| 0.057
| 0.030
|}

 

The endo product is shown here to have both a lower activation energy and a large change in gibbs energy meaning that it is both the kinetic and thermodynamic product.
This is because in the endo product the p-orbitals on the oxygen of the 1,3-dioxole are interacting with the pi orbitals of the new carbon-carbon double bond resulting in a stabilised transition state. Furthermore there is steric hinderance in the exo transition state between the two oxygen atoms and ethane bridge.

==Exercise 3: Diels-Alder vs Cheletropic==

 

[[File:MaxbReactionScheme3.jpg|centre]]

 

===Diels-Alder: EXO===
Reaction Coordinate:

 

[[File:MaxbEXOIRC.gif]]

====IRC Path====

[[File:Total Energy along IRC EXO.pdf]]
[[Media:REACTANTSEXOIRC.LOG]]
====Energy Profile for Exo Product====

[[File:MaxbEXO.jpg]]

 

===Diels-Alder: Endo===

[[File:MaxbENDOIRC.gif]]

====IRC Path====

[[File:Total Energy along IRC ENDO.pdf]]
[[Media:REACTANTSENDOIRC.LOG]]

The IRC shown here is in reverse resulting in it going from products to reactants.

====Energy Profile for Endo Product====

[[File:MaxbENDO.jpg]]

 

The IRCs of both the endo and exo reactions show the formation of a new six membered ring. It can be seen in both reaction paths that there is a delocalistion of electrons throughout the xylylene due to it being highly unstable. The reaction paths show that the exo- product is favored kinetically and thermodynamically due to it having a lower activation energy and large change in gibbs energy.

 

===Cheletropic reaction===

[[File:MaxbCHELOIRC.gif]]

====IRC Path====
[[File:Total Energy along IRC CHELO.pdf]]

====Energy Profile for Chelotropic reaction====

[[File:MaxbCHELO.jpg]]

 

The chelotropic reaction shows a higher activation energy in comparison to the diels-alder reaction, this is down to a five membered ring forming which is more strained than the 6 membered ring formed in the diels-alder reaction. The chelotropic reaction has a much higher change in gibbs energy than the diels-alder reaction meaning that the chelotropic product would form under thermodynamic control and the diels-alder under kinetic control.

Rep:Mod:MaxBridge

2017-03-11T18:06:20Z

Mhb314: /* Energy Profile for Endo Product */

== '''Introduction''' ==

A potential energy surface (PES) is used to show the energy of a system as a function pof the positions of the atoms in that system.
A PES can be used to determine whether a transition state occurs during a reaction, in which a species is made that is different to the reactants and the products. When evaluating the stationary points on a PES, ie when the gradient is zero, it is found that the minima points are where the reactants and products are located and the maxima occurs when a transition state occurs. To confirm where the minima and maxima are the second derivative is taken and are found to be postive and negative respectively. Furthermore through using gaussian it can be shown that a transition sate will a negative frequency and the reactants and products will not.

During this report there will be three different exercises explored using Gaussian in which the reactants, products and transition states were all optimised at the PM6 level along with frequency calculations also performed. For exercise 2 the products were also ran at the B3LYP/6-31(d) level. An IRC calculation was ran for every reaction in order to show the reaction coordinate.

== Exercise 1: Reaction of Butadiene with Ethylene ==

[[File:Reaction scheme.jpg]]

This reaction has been analyzed by optimizing the reactants and transition state using Gaussian at the PM6 level. The presence of a transition state was confirmed by running a frequency calculation at the PM6 level of the transition state and a negative frequency of -948.80 being shown.

==='''Molecular Orbital Analysis'''===

[[File:MaxbMODiagram.jpg]]

The molecular orbital diagram shows the HOMO and LUMO of both reactants and the transition state.

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO of Butadiene and Ethylene
|-
| style="text-align: center;"|HOMO of Butadiene
| style="text-align: center;"|LUMO of Butadiene
| style="text-align: center;"|HOMO of Ethylene
| style="text-align: center;"|LUMO of Ethylene
|-
| align="center"|[[File:MaxbButadieneHOMO.jpg|250px]]
| align="center"|[[File:MaxbButadieneLUMO.jpg|250px]]
| align="center"|[[File:MaxbEtheneHOMO.jpg|250px]]
| align="center"|[[File:MaxBEtheneLUMO.jpg|250px]]
|}
[[Media:ETHENEOPTMAXB.LOG]]
[[Media:BUTADIENEOPTMAXB.LOG]]
 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ Molecular Orbitals of the Transition State
|-
| style="text-align: center;"|MO 16 of TS
| style="text-align: center;"|HOMO of TS
| style="text-align: center;"|LUMO of TS
| style="text-align: center;"|MO 19 of TS
|-
| align="center"|[[File:MaxbTSMO16.jpg|250px]]
| align="center"|[[File:MaxbTSHOMO.jpg|250px]]
| align="center"|[[File:MaxbTSLUMO.jpg|250px]]
| align="center"|[[File:MaxbTSMO19.jpg|250px]]
|}
[[Media:BUTAANDETHANETS.LOG]]

 

The HOMO of the ethylene and the LUMO of the butadiene are both of gerade symmetry so they interact to produce molecular orbitals shown above. The HOMO of the butadiene and the LUMO of the ethylene are both of ungerade symmetry so they interact to give molecular orbital shown above. This follows a typical Diels-Alder reaction as the HOMO of butadiene is of higher energy than the HOMO of the ethylene.

===Bond Length Analysis===

{| class="wikitable" style="margin: 1em auto 1em auto;"
! rowspan="2" style="text-align: center;" | Carbon Bonds
! colspan="3" style="text-align: center;" | Bond Length (Å)
|-
| style="text-align: center;" | Reactants
| style="text-align: center;" | Transition State
| style="text-align: center;" | Product
|-
| C1-C2
| style="text-align: center;" | 1.33528
| style="text-align: center;" | 1.37980
| style="text-align: center;" | 1.50090
|-
| C2-C3
| style="text-align: center;" | 1.46837
| style="text-align: center;" | 1.41112
| style="text-align: center;" | 1.33784
|-
| C3-C4
| style="text-align: center;" | 1.33528
| style="text-align: center;" | 1.37979
| style="text-align: center;" | 1.50090
|-
| C4-C5
| style="text-align: center;" | n/a
| style="text-align: center;" | 2.11464
| style="text-align: center;" | 1.54040
|-
| C5-C6
| style="text-align: center;" | 1.32741
| style="text-align: center;" | 1.38177
| style="text-align: center;" | 1.54091
|-
| C6-C1
| style="text-align: center;" | n/a
| style="text-align: center;" | 2.11482
| style="text-align: center;" | 1.54040
|}

==='''Transition State'''===
 

[[File:ButaEthaneTSMB.gif|center]]
[[MediaːBUTAANDETHANETS.LOG]]

 

The above vibration shows that the new C-C bonds form synchronously as the C-C bond of the butadiene is compressed whilst the terminal carbon atoms of each reactant move closer together simultaneously.

==='''Reaction Path'''===

==Exercise 2ː Reaction of Cyclohexadiene and 1,3-Dioxole==

 

[[File:MaxBScheme2.jpg]]
 

The reactants, transition states and the exo- and endo- adducts of the product were optimized to the B3LYP/6-31G(d) level on Gaussian.

 

==='''Molecular Orbital Analysis'''===

 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO of Cyclohexadiene and 1,3-Dioxole
|-
| style="text-align: center;"|HOMO of Cyclohexadiene
| style="text-align: center;"|LUMO of Cyclohexadiene
| style="text-align: center;"|HOMO of 1,3-Dioxole
| style="text-align: center;"|LUMO of 1,3-Dioxole
|-
| align="center"|[[File:MaxbButadieneHOMO.jpg|250px]]
| align="center"|[[File:MaxbHEXALUMO.jpg|250px]]
| align="center"|[[File:MaxbOXYHOMO.jpg|250px]]
| align="center"|[[File:MaxbOXYLUMO.jpg|250px]]
|}
[[Media:CYCLOOXYGEN2.LOG]]
[[Media:CYCLOHEXADIENEDFTMAXB.LOG]]

 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO Endo- and Exo- Trasition States
|-
| style="text-align: center;"|HOMO of EXO-
| style="text-align: center;"|LUMO of EXO-
| style="text-align: center;"|HOMO of ENDO-
| style="text-align: center;"|LUMO of ENDO-
|-
| align="center"|[[File:MaxbEXOHOMO.jpg|250px]]
| align="center"|[[File:MaxBEXOLUMO.jpg|250px]]
| align="center"|[[File:MaxbENDOHOMO.jpg|250px]]
| align="center"|[[File:MaxbENDOLUMO.jpg|250px]]
|}

[[Media:REACTANTS TS B3LPY.LOG]]
[[Media:REACTANTS ENDO TS B3LPY.LOG]]

 

This reaction is between an electron rich dienophile (Cyclohexadiene) and an electron-poor diene (1,3-Dioxole) meaning that an inverse electron demand Diels-Alder reaction occurs. The main difference between the molecular orbitals in an inverse and a standard Diels-Alder reaction is that in an inverse reaction the HOMO of the diene is lower in energy than the LUMO of the Dienophile.

==='''Thermochemistry'''===
 

{| class="wikitable" style="margin: 1em auto 1em auto;"
! style="font-weight: bold;" |
! style="font-weight: bold;" | Reactants
! style="font-weight: bold;" | Transition State
! style="font-weight: bold;" | Product
! style="font-weight: bold;" | Ea
! style="font-weight: bold;" | ΔGr
|-
| Exo
| -500.389165
| -500.329168
| -500.417323
| 0.060
| 0.028
|-
| Endo
| -500.389165
| -500.332111
| -500.418691
| 0.057
| 0.030
|}

 

The endo product is shown here to have both a lower activation energy and a large change in gibbs energy meaning that it is both the kinetic and thermodynamic product.
This is because in the endo product the p-orbitals on the oxygen of the 1,3-dioxole are interacting with the pi orbitals of the new carbon-carbon double bond resulting in a stabilised transition state. Furthermore there is steric hinderance in the exo transition state between the two oxygen atoms and ethane bridge.

==Exercise 3: Diels-Alder vs Cheletropic==

 

[[File:MaxbReactionScheme3.jpg|centre]]

 

===Diels-Alder: EXO===
Reaction Coordinate:

 

[[File:MaxbEXOIRC.gif]]

====IRC Path====

[[File:Total Energy along IRC EXO.pdf]]
[[Media:REACTANTSEXOIRC.LOG]]
====Energy Profile for Exo Product====

[[File:MaxbEXO.jpg]]

 

===Diels-Alder: Endo===

[[File:MaxbENDOIRC.gif]]

====IRC Path====

[[File:Total Energy along IRC ENDO.pdf]]
[[Media:REACTANTSENDOIRC.LOG]]

The IRC shown here is in reverse resulting in it going from products to reactants.

====Energy Profile for Endo Product====

[[File:MaxbENDO.jpg]]

 

The IRCs of both the endo and exo reactions show the formation of a new six membered ring

===Cheletropic reaction===

[[File:MaxbCHELOIRC.gif]]

====IRC Path====
[[File:Total Energy along IRC CHELO.pdf]]

====Energy Profile for Chelotropic reaction====

[[File:MaxbCHELO.jpg]]

Rep:Mod:MaxBridge

2017-03-11T18:01:57Z

Mhb314: /* IRC Path */

== '''Introduction''' ==

A potential energy surface (PES) is used to show the energy of a system as a function pof the positions of the atoms in that system.
A PES can be used to determine whether a transition state occurs during a reaction, in which a species is made that is different to the reactants and the products. When evaluating the stationary points on a PES, ie when the gradient is zero, it is found that the minima points are where the reactants and products are located and the maxima occurs when a transition state occurs. To confirm where the minima and maxima are the second derivative is taken and are found to be postive and negative respectively. Furthermore through using gaussian it can be shown that a transition sate will a negative frequency and the reactants and products will not.

During this report there will be three different exercises explored using Gaussian in which the reactants, products and transition states were all optimised at the PM6 level along with frequency calculations also performed. For exercise 2 the products were also ran at the B3LYP/6-31(d) level. An IRC calculation was ran for every reaction in order to show the reaction coordinate.

== Exercise 1: Reaction of Butadiene with Ethylene ==

[[File:Reaction scheme.jpg]]

This reaction has been analyzed by optimizing the reactants and transition state using Gaussian at the PM6 level. The presence of a transition state was confirmed by running a frequency calculation at the PM6 level of the transition state and a negative frequency of -948.80 being shown.

==='''Molecular Orbital Analysis'''===

[[File:MaxbMODiagram.jpg]]

The molecular orbital diagram shows the HOMO and LUMO of both reactants and the transition state.

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO of Butadiene and Ethylene
|-
| style="text-align: center;"|HOMO of Butadiene
| style="text-align: center;"|LUMO of Butadiene
| style="text-align: center;"|HOMO of Ethylene
| style="text-align: center;"|LUMO of Ethylene
|-
| align="center"|[[File:MaxbButadieneHOMO.jpg|250px]]
| align="center"|[[File:MaxbButadieneLUMO.jpg|250px]]
| align="center"|[[File:MaxbEtheneHOMO.jpg|250px]]
| align="center"|[[File:MaxBEtheneLUMO.jpg|250px]]
|}
[[Media:ETHENEOPTMAXB.LOG]]
[[Media:BUTADIENEOPTMAXB.LOG]]
 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ Molecular Orbitals of the Transition State
|-
| style="text-align: center;"|MO 16 of TS
| style="text-align: center;"|HOMO of TS
| style="text-align: center;"|LUMO of TS
| style="text-align: center;"|MO 19 of TS
|-
| align="center"|[[File:MaxbTSMO16.jpg|250px]]
| align="center"|[[File:MaxbTSHOMO.jpg|250px]]
| align="center"|[[File:MaxbTSLUMO.jpg|250px]]
| align="center"|[[File:MaxbTSMO19.jpg|250px]]
|}
[[Media:BUTAANDETHANETS.LOG]]

 

The HOMO of the ethylene and the LUMO of the butadiene are both of gerade symmetry so they interact to produce molecular orbitals shown above. The HOMO of the butadiene and the LUMO of the ethylene are both of ungerade symmetry so they interact to give molecular orbital shown above. This follows a typical Diels-Alder reaction as the HOMO of butadiene is of higher energy than the HOMO of the ethylene.

===Bond Length Analysis===

{| class="wikitable" style="margin: 1em auto 1em auto;"
! rowspan="2" style="text-align: center;" | Carbon Bonds
! colspan="3" style="text-align: center;" | Bond Length (Å)
|-
| style="text-align: center;" | Reactants
| style="text-align: center;" | Transition State
| style="text-align: center;" | Product
|-
| C1-C2
| style="text-align: center;" | 1.33528
| style="text-align: center;" | 1.37980
| style="text-align: center;" | 1.50090
|-
| C2-C3
| style="text-align: center;" | 1.46837
| style="text-align: center;" | 1.41112
| style="text-align: center;" | 1.33784
|-
| C3-C4
| style="text-align: center;" | 1.33528
| style="text-align: center;" | 1.37979
| style="text-align: center;" | 1.50090
|-
| C4-C5
| style="text-align: center;" | n/a
| style="text-align: center;" | 2.11464
| style="text-align: center;" | 1.54040
|-
| C5-C6
| style="text-align: center;" | 1.32741
| style="text-align: center;" | 1.38177
| style="text-align: center;" | 1.54091
|-
| C6-C1
| style="text-align: center;" | n/a
| style="text-align: center;" | 2.11482
| style="text-align: center;" | 1.54040
|}

==='''Transition State'''===
 

[[File:ButaEthaneTSMB.gif|center]]
[[MediaːBUTAANDETHANETS.LOG]]

 

The above vibration shows that the new C-C bonds form synchronously as the C-C bond of the butadiene is compressed whilst the terminal carbon atoms of each reactant move closer together simultaneously.

==='''Reaction Path'''===

==Exercise 2ː Reaction of Cyclohexadiene and 1,3-Dioxole==

 

[[File:MaxBScheme2.jpg]]
 

The reactants, transition states and the exo- and endo- adducts of the product were optimized to the B3LYP/6-31G(d) level on Gaussian.

 

==='''Molecular Orbital Analysis'''===

 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO of Cyclohexadiene and 1,3-Dioxole
|-
| style="text-align: center;"|HOMO of Cyclohexadiene
| style="text-align: center;"|LUMO of Cyclohexadiene
| style="text-align: center;"|HOMO of 1,3-Dioxole
| style="text-align: center;"|LUMO of 1,3-Dioxole
|-
| align="center"|[[File:MaxbButadieneHOMO.jpg|250px]]
| align="center"|[[File:MaxbHEXALUMO.jpg|250px]]
| align="center"|[[File:MaxbOXYHOMO.jpg|250px]]
| align="center"|[[File:MaxbOXYLUMO.jpg|250px]]
|}
[[Media:CYCLOOXYGEN2.LOG]]
[[Media:CYCLOHEXADIENEDFTMAXB.LOG]]

 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO Endo- and Exo- Trasition States
|-
| style="text-align: center;"|HOMO of EXO-
| style="text-align: center;"|LUMO of EXO-
| style="text-align: center;"|HOMO of ENDO-
| style="text-align: center;"|LUMO of ENDO-
|-
| align="center"|[[File:MaxbEXOHOMO.jpg|250px]]
| align="center"|[[File:MaxBEXOLUMO.jpg|250px]]
| align="center"|[[File:MaxbENDOHOMO.jpg|250px]]
| align="center"|[[File:MaxbENDOLUMO.jpg|250px]]
|}

[[Media:REACTANTS TS B3LPY.LOG]]
[[Media:REACTANTS ENDO TS B3LPY.LOG]]

 

This reaction is between an electron rich dienophile (Cyclohexadiene) and an electron-poor diene (1,3-Dioxole) meaning that an inverse electron demand Diels-Alder reaction occurs. The main difference between the molecular orbitals in an inverse and a standard Diels-Alder reaction is that in an inverse reaction the HOMO of the diene is lower in energy than the LUMO of the Dienophile.

==='''Thermochemistry'''===
 

{| class="wikitable" style="margin: 1em auto 1em auto;"
! style="font-weight: bold;" |
! style="font-weight: bold;" | Reactants
! style="font-weight: bold;" | Transition State
! style="font-weight: bold;" | Product
! style="font-weight: bold;" | Ea
! style="font-weight: bold;" | ΔGr
|-
| Exo
| -500.389165
| -500.329168
| -500.417323
| 0.060
| 0.028
|-
| Endo
| -500.389165
| -500.332111
| -500.418691
| 0.057
| 0.030
|}

 

The endo product is shown here to have both a lower activation energy and a large change in gibbs energy meaning that it is both the kinetic and thermodynamic product.
This is because in the endo product the p-orbitals on the oxygen of the 1,3-dioxole are interacting with the pi orbitals of the new carbon-carbon double bond resulting in a stabilised transition state. Furthermore there is steric hinderance in the exo transition state between the two oxygen atoms and ethane bridge.

==Exercise 3: Diels-Alder vs Cheletropic==

 

[[File:MaxbReactionScheme3.jpg|centre]]

 

===Diels-Alder: EXO===
Reaction Coordinate:

 

[[File:MaxbEXOIRC.gif]]

====IRC Path====

[[File:Total Energy along IRC EXO.pdf]]
[[Media:REACTANTSEXOIRC.LOG]]
====Energy Profile for Exo Product====

[[File:MaxbEXO.jpg]]

 

===Diels-Alder: Endo===

[[File:MaxbENDOIRC.gif]]

====IRC Path====

[[File:Total Energy along IRC ENDO.pdf]]
[[Media:REACTANTSENDOIRC.LOG]]

The IRC shown here is in reverse resulting in it going from products to reactants.

====Energy Profile for Endo Product====

[[File:MaxbENDO.jpg]]

 

===Cheletropic reaction===

[[File:MaxbCHELOIRC.gif]]

====IRC Path====
[[File:Total Energy along IRC CHELO.pdf]]

====Energy Profile for Chelotropic reaction====

[[File:MaxbCHELO.jpg]]

Rep:Mod:MaxBridge

2017-03-11T18:01:41Z

Mhb314: /* Exercise 3: Diels-Alder vs Cheletropic */

== '''Introduction''' ==

A potential energy surface (PES) is used to show the energy of a system as a function pof the positions of the atoms in that system.
A PES can be used to determine whether a transition state occurs during a reaction, in which a species is made that is different to the reactants and the products. When evaluating the stationary points on a PES, ie when the gradient is zero, it is found that the minima points are where the reactants and products are located and the maxima occurs when a transition state occurs. To confirm where the minima and maxima are the second derivative is taken and are found to be postive and negative respectively. Furthermore through using gaussian it can be shown that a transition sate will a negative frequency and the reactants and products will not.

During this report there will be three different exercises explored using Gaussian in which the reactants, products and transition states were all optimised at the PM6 level along with frequency calculations also performed. For exercise 2 the products were also ran at the B3LYP/6-31(d) level. An IRC calculation was ran for every reaction in order to show the reaction coordinate.

== Exercise 1: Reaction of Butadiene with Ethylene ==

[[File:Reaction scheme.jpg]]

This reaction has been analyzed by optimizing the reactants and transition state using Gaussian at the PM6 level. The presence of a transition state was confirmed by running a frequency calculation at the PM6 level of the transition state and a negative frequency of -948.80 being shown.

==='''Molecular Orbital Analysis'''===

[[File:MaxbMODiagram.jpg]]

The molecular orbital diagram shows the HOMO and LUMO of both reactants and the transition state.

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO of Butadiene and Ethylene
|-
| style="text-align: center;"|HOMO of Butadiene
| style="text-align: center;"|LUMO of Butadiene
| style="text-align: center;"|HOMO of Ethylene
| style="text-align: center;"|LUMO of Ethylene
|-
| align="center"|[[File:MaxbButadieneHOMO.jpg|250px]]
| align="center"|[[File:MaxbButadieneLUMO.jpg|250px]]
| align="center"|[[File:MaxbEtheneHOMO.jpg|250px]]
| align="center"|[[File:MaxBEtheneLUMO.jpg|250px]]
|}
[[Media:ETHENEOPTMAXB.LOG]]
[[Media:BUTADIENEOPTMAXB.LOG]]
 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ Molecular Orbitals of the Transition State
|-
| style="text-align: center;"|MO 16 of TS
| style="text-align: center;"|HOMO of TS
| style="text-align: center;"|LUMO of TS
| style="text-align: center;"|MO 19 of TS
|-
| align="center"|[[File:MaxbTSMO16.jpg|250px]]
| align="center"|[[File:MaxbTSHOMO.jpg|250px]]
| align="center"|[[File:MaxbTSLUMO.jpg|250px]]
| align="center"|[[File:MaxbTSMO19.jpg|250px]]
|}
[[Media:BUTAANDETHANETS.LOG]]

 

The HOMO of the ethylene and the LUMO of the butadiene are both of gerade symmetry so they interact to produce molecular orbitals shown above. The HOMO of the butadiene and the LUMO of the ethylene are both of ungerade symmetry so they interact to give molecular orbital shown above. This follows a typical Diels-Alder reaction as the HOMO of butadiene is of higher energy than the HOMO of the ethylene.

===Bond Length Analysis===

{| class="wikitable" style="margin: 1em auto 1em auto;"
! rowspan="2" style="text-align: center;" | Carbon Bonds
! colspan="3" style="text-align: center;" | Bond Length (Å)
|-
| style="text-align: center;" | Reactants
| style="text-align: center;" | Transition State
| style="text-align: center;" | Product
|-
| C1-C2
| style="text-align: center;" | 1.33528
| style="text-align: center;" | 1.37980
| style="text-align: center;" | 1.50090
|-
| C2-C3
| style="text-align: center;" | 1.46837
| style="text-align: center;" | 1.41112
| style="text-align: center;" | 1.33784
|-
| C3-C4
| style="text-align: center;" | 1.33528
| style="text-align: center;" | 1.37979
| style="text-align: center;" | 1.50090
|-
| C4-C5
| style="text-align: center;" | n/a
| style="text-align: center;" | 2.11464
| style="text-align: center;" | 1.54040
|-
| C5-C6
| style="text-align: center;" | 1.32741
| style="text-align: center;" | 1.38177
| style="text-align: center;" | 1.54091
|-
| C6-C1
| style="text-align: center;" | n/a
| style="text-align: center;" | 2.11482
| style="text-align: center;" | 1.54040
|}

==='''Transition State'''===
 

[[File:ButaEthaneTSMB.gif|center]]
[[MediaːBUTAANDETHANETS.LOG]]

 

The above vibration shows that the new C-C bonds form synchronously as the C-C bond of the butadiene is compressed whilst the terminal carbon atoms of each reactant move closer together simultaneously.

==='''Reaction Path'''===

==Exercise 2ː Reaction of Cyclohexadiene and 1,3-Dioxole==

 

[[File:MaxBScheme2.jpg]]
 

The reactants, transition states and the exo- and endo- adducts of the product were optimized to the B3LYP/6-31G(d) level on Gaussian.

 

==='''Molecular Orbital Analysis'''===

 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO of Cyclohexadiene and 1,3-Dioxole
|-
| style="text-align: center;"|HOMO of Cyclohexadiene
| style="text-align: center;"|LUMO of Cyclohexadiene
| style="text-align: center;"|HOMO of 1,3-Dioxole
| style="text-align: center;"|LUMO of 1,3-Dioxole
|-
| align="center"|[[File:MaxbButadieneHOMO.jpg|250px]]
| align="center"|[[File:MaxbHEXALUMO.jpg|250px]]
| align="center"|[[File:MaxbOXYHOMO.jpg|250px]]
| align="center"|[[File:MaxbOXYLUMO.jpg|250px]]
|}
[[Media:CYCLOOXYGEN2.LOG]]
[[Media:CYCLOHEXADIENEDFTMAXB.LOG]]

 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO Endo- and Exo- Trasition States
|-
| style="text-align: center;"|HOMO of EXO-
| style="text-align: center;"|LUMO of EXO-
| style="text-align: center;"|HOMO of ENDO-
| style="text-align: center;"|LUMO of ENDO-
|-
| align="center"|[[File:MaxbEXOHOMO.jpg|250px]]
| align="center"|[[File:MaxBEXOLUMO.jpg|250px]]
| align="center"|[[File:MaxbENDOHOMO.jpg|250px]]
| align="center"|[[File:MaxbENDOLUMO.jpg|250px]]
|}

[[Media:REACTANTS TS B3LPY.LOG]]
[[Media:REACTANTS ENDO TS B3LPY.LOG]]

 

This reaction is between an electron rich dienophile (Cyclohexadiene) and an electron-poor diene (1,3-Dioxole) meaning that an inverse electron demand Diels-Alder reaction occurs. The main difference between the molecular orbitals in an inverse and a standard Diels-Alder reaction is that in an inverse reaction the HOMO of the diene is lower in energy than the LUMO of the Dienophile.

==='''Thermochemistry'''===
 

{| class="wikitable" style="margin: 1em auto 1em auto;"
! style="font-weight: bold;" |
! style="font-weight: bold;" | Reactants
! style="font-weight: bold;" | Transition State
! style="font-weight: bold;" | Product
! style="font-weight: bold;" | Ea
! style="font-weight: bold;" | ΔGr
|-
| Exo
| -500.389165
| -500.329168
| -500.417323
| 0.060
| 0.028
|-
| Endo
| -500.389165
| -500.332111
| -500.418691
| 0.057
| 0.030
|}

 

The endo product is shown here to have both a lower activation energy and a large change in gibbs energy meaning that it is both the kinetic and thermodynamic product.
This is because in the endo product the p-orbitals on the oxygen of the 1,3-dioxole are interacting with the pi orbitals of the new carbon-carbon double bond resulting in a stabilised transition state. Furthermore there is steric hinderance in the exo transition state between the two oxygen atoms and ethane bridge.

==Exercise 3: Diels-Alder vs Cheletropic==

 

[[File:MaxbReactionScheme3.jpg|centre]]

 

===Diels-Alder: EXO===
Reaction Coordinate:

 

[[File:MaxbEXOIRC.gif]]

====IRC Path====

[[File:Total Energy along IRC EXO.pdf]]
[[Media:REACTANTSEXOIRC.LOG]]
====Energy Profile for Exo Product====

[[File:MaxbEXO.jpg]]

 

===Diels-Alder: Endo===

[[File:MaxbENDOIRC.gif]]

====IRC Path====

[[File:Total Energy along IRC ENDO.pdf]]
[[Media:REACTANTSENDOIRC.LOG]]

The IRC shown here is in reverse resulting in it going from products to reactants.

====Energy Profile for Endo Product====

[[File:MaxbENDO.jpg]]

 

===Cheletropic reaction===

[[File:MaxbCHELOIRC.gif]]

====IRC Path====
[[File:Total Energy along IRC CHELO.pdf

====Energy Profile for Chelotropic reaction====

[[File:MaxbCHELO.jpg]]

File:MaxbCHELO.jpg

2017-03-11T18:01:21Z

Mhb314:

File:Total Energy along IRC CHELO.pdf

2017-03-11T17:56:06Z

Mhb314:

File:MaxbCHELOIRC.gif

2017-03-11T17:51:48Z

Mhb314:

File:MaxbENDO.jpg

2017-03-11T17:49:52Z

Mhb314:

File:REACTANTSENDOIRC.LOG

2017-03-11T17:45:53Z

Mhb314:

File:Total Energy along IRC ENDO.pdf

2017-03-11T17:44:51Z

Mhb314:

File:MaxbENDOIRC.gif

2017-03-11T17:42:43Z

Mhb314:

File:REACTANTSEXOIRC.LOG

2017-03-11T17:41:36Z

Mhb314:

File:MaxbEXO.jpg

2017-03-11T17:37:44Z

Mhb314:

File:Total Energy along IRC EXO.pdf

2017-03-11T17:07:33Z

Mhb314:

File:MaxbEXOIRC.gif

2017-03-11T16:56:07Z

Mhb314:

Rep:Mod:MaxBridge

2017-03-11T16:55:28Z

Mhb314: /* Thermochemistry */

== '''Introduction''' ==

A potential energy surface (PES) is used to show the energy of a system as a function pof the positions of the atoms in that system.
A PES can be used to determine whether a transition state occurs during a reaction, in which a species is made that is different to the reactants and the products. When evaluating the stationary points on a PES, ie when the gradient is zero, it is found that the minima points are where the reactants and products are located and the maxima occurs when a transition state occurs. To confirm where the minima and maxima are the second derivative is taken and are found to be postive and negative respectively. Furthermore through using gaussian it can be shown that a transition sate will a negative frequency and the reactants and products will not.

During this report there will be three different exercises explored using Gaussian in which the reactants, products and transition states were all optimised at the PM6 level along with frequency calculations also performed. For exercise 2 the products were also ran at the B3LYP/6-31(d) level. An IRC calculation was ran for every reaction in order to show the reaction coordinate.

== Exercise 1: Reaction of Butadiene with Ethylene ==

[[File:Reaction scheme.jpg]]

This reaction has been analyzed by optimizing the reactants and transition state using Gaussian at the PM6 level. The presence of a transition state was confirmed by running a frequency calculation at the PM6 level of the transition state and a negative frequency of -948.80 being shown.

==='''Molecular Orbital Analysis'''===

[[File:MaxbMODiagram.jpg]]

The molecular orbital diagram shows the HOMO and LUMO of both reactants and the transition state.

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO of Butadiene and Ethylene
|-
| style="text-align: center;"|HOMO of Butadiene
| style="text-align: center;"|LUMO of Butadiene
| style="text-align: center;"|HOMO of Ethylene
| style="text-align: center;"|LUMO of Ethylene
|-
| align="center"|[[File:MaxbButadieneHOMO.jpg|250px]]
| align="center"|[[File:MaxbButadieneLUMO.jpg|250px]]
| align="center"|[[File:MaxbEtheneHOMO.jpg|250px]]
| align="center"|[[File:MaxBEtheneLUMO.jpg|250px]]
|}
[[Media:ETHENEOPTMAXB.LOG]]
[[Media:BUTADIENEOPTMAXB.LOG]]
 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ Molecular Orbitals of the Transition State
|-
| style="text-align: center;"|MO 16 of TS
| style="text-align: center;"|HOMO of TS
| style="text-align: center;"|LUMO of TS
| style="text-align: center;"|MO 19 of TS
|-
| align="center"|[[File:MaxbTSMO16.jpg|250px]]
| align="center"|[[File:MaxbTSHOMO.jpg|250px]]
| align="center"|[[File:MaxbTSLUMO.jpg|250px]]
| align="center"|[[File:MaxbTSMO19.jpg|250px]]
|}
[[Media:BUTAANDETHANETS.LOG]]

 

The HOMO of the ethylene and the LUMO of the butadiene are both of gerade symmetry so they interact to produce molecular orbitals shown above. The HOMO of the butadiene and the LUMO of the ethylene are both of ungerade symmetry so they interact to give molecular orbital shown above. This follows a typical Diels-Alder reaction as the HOMO of butadiene is of higher energy than the HOMO of the ethylene.

===Bond Length Analysis===

{| class="wikitable" style="margin: 1em auto 1em auto;"
! rowspan="2" style="text-align: center;" | Carbon Bonds
! colspan="3" style="text-align: center;" | Bond Length (Å)
|-
| style="text-align: center;" | Reactants
| style="text-align: center;" | Transition State
| style="text-align: center;" | Product
|-
| C1-C2
| style="text-align: center;" | 1.33528
| style="text-align: center;" | 1.37980
| style="text-align: center;" | 1.50090
|-
| C2-C3
| style="text-align: center;" | 1.46837
| style="text-align: center;" | 1.41112
| style="text-align: center;" | 1.33784
|-
| C3-C4
| style="text-align: center;" | 1.33528
| style="text-align: center;" | 1.37979
| style="text-align: center;" | 1.50090
|-
| C4-C5
| style="text-align: center;" | n/a
| style="text-align: center;" | 2.11464
| style="text-align: center;" | 1.54040
|-
| C5-C6
| style="text-align: center;" | 1.32741
| style="text-align: center;" | 1.38177
| style="text-align: center;" | 1.54091
|-
| C6-C1
| style="text-align: center;" | n/a
| style="text-align: center;" | 2.11482
| style="text-align: center;" | 1.54040
|}

==='''Transition State'''===
 

[[File:ButaEthaneTSMB.gif|center]]
[[MediaːBUTAANDETHANETS.LOG]]

 

The above vibration shows that the new C-C bonds form synchronously as the C-C bond of the butadiene is compressed whilst the terminal carbon atoms of each reactant move closer together simultaneously.

==='''Reaction Path'''===

==Exercise 2ː Reaction of Cyclohexadiene and 1,3-Dioxole==

 

[[File:MaxBScheme2.jpg]]
 

The reactants, transition states and the exo- and endo- adducts of the product were optimized to the B3LYP/6-31G(d) level on Gaussian.

 

==='''Molecular Orbital Analysis'''===

 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO of Cyclohexadiene and 1,3-Dioxole
|-
| style="text-align: center;"|HOMO of Cyclohexadiene
| style="text-align: center;"|LUMO of Cyclohexadiene
| style="text-align: center;"|HOMO of 1,3-Dioxole
| style="text-align: center;"|LUMO of 1,3-Dioxole
|-
| align="center"|[[File:MaxbButadieneHOMO.jpg|250px]]
| align="center"|[[File:MaxbHEXALUMO.jpg|250px]]
| align="center"|[[File:MaxbOXYHOMO.jpg|250px]]
| align="center"|[[File:MaxbOXYLUMO.jpg|250px]]
|}
[[Media:CYCLOOXYGEN2.LOG]]
[[Media:CYCLOHEXADIENEDFTMAXB.LOG]]

 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO Endo- and Exo- Trasition States
|-
| style="text-align: center;"|HOMO of EXO-
| style="text-align: center;"|LUMO of EXO-
| style="text-align: center;"|HOMO of ENDO-
| style="text-align: center;"|LUMO of ENDO-
|-
| align="center"|[[File:MaxbEXOHOMO.jpg|250px]]
| align="center"|[[File:MaxBEXOLUMO.jpg|250px]]
| align="center"|[[File:MaxbENDOHOMO.jpg|250px]]
| align="center"|[[File:MaxbENDOLUMO.jpg|250px]]
|}

[[Media:REACTANTS TS B3LPY.LOG]]
[[Media:REACTANTS ENDO TS B3LPY.LOG]]

 

This reaction is between an electron rich dienophile (Cyclohexadiene) and an electron-poor diene (1,3-Dioxole) meaning that an inverse electron demand Diels-Alder reaction occurs. The main difference between the molecular orbitals in an inverse and a standard Diels-Alder reaction is that in an inverse reaction the HOMO of the diene is lower in energy than the LUMO of the Dienophile.

==='''Thermochemistry'''===
 

{| class="wikitable" style="margin: 1em auto 1em auto;"
! style="font-weight: bold;" |
! style="font-weight: bold;" | Reactants
! style="font-weight: bold;" | Transition State
! style="font-weight: bold;" | Product
! style="font-weight: bold;" | Ea
! style="font-weight: bold;" | ΔGr
|-
| Exo
| -500.389165
| -500.329168
| -500.417323
| 0.060
| 0.028
|-
| Endo
| -500.389165
| -500.332111
| -500.418691
| 0.057
| 0.030
|}

 

The endo product is shown here to have both a lower activation energy and a large change in gibbs energy meaning that it is both the kinetic and thermodynamic product.
This is because in the endo product the p-orbitals on the oxygen of the 1,3-dioxole are interacting with the pi orbitals of the new carbon-carbon double bond resulting in a stabilised transition state. Furthermore there is steric hinderance in the exo transition state between the two oxygen atoms and ethane bridge.

==Exercise 3: Diels-Alder vs Cheletropic==

 

[[File:MaxbReactionScheme3.jpg|centre]]

Rep:Mod:MaxBridge

2017-03-11T16:55:11Z

Mhb314: /* Exercise 3: Diels-Alder vs Cheletropic */

== '''Introduction''' ==

A potential energy surface (PES) is used to show the energy of a system as a function pof the positions of the atoms in that system.
A PES can be used to determine whether a transition state occurs during a reaction, in which a species is made that is different to the reactants and the products. When evaluating the stationary points on a PES, ie when the gradient is zero, it is found that the minima points are where the reactants and products are located and the maxima occurs when a transition state occurs. To confirm where the minima and maxima are the second derivative is taken and are found to be postive and negative respectively. Furthermore through using gaussian it can be shown that a transition sate will a negative frequency and the reactants and products will not.

During this report there will be three different exercises explored using Gaussian in which the reactants, products and transition states were all optimised at the PM6 level along with frequency calculations also performed. For exercise 2 the products were also ran at the B3LYP/6-31(d) level. An IRC calculation was ran for every reaction in order to show the reaction coordinate.

== Exercise 1: Reaction of Butadiene with Ethylene ==

[[File:Reaction scheme.jpg]]

This reaction has been analyzed by optimizing the reactants and transition state using Gaussian at the PM6 level. The presence of a transition state was confirmed by running a frequency calculation at the PM6 level of the transition state and a negative frequency of -948.80 being shown.

==='''Molecular Orbital Analysis'''===

[[File:MaxbMODiagram.jpg]]

The molecular orbital diagram shows the HOMO and LUMO of both reactants and the transition state.

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO of Butadiene and Ethylene
|-
| style="text-align: center;"|HOMO of Butadiene
| style="text-align: center;"|LUMO of Butadiene
| style="text-align: center;"|HOMO of Ethylene
| style="text-align: center;"|LUMO of Ethylene
|-
| align="center"|[[File:MaxbButadieneHOMO.jpg|250px]]
| align="center"|[[File:MaxbButadieneLUMO.jpg|250px]]
| align="center"|[[File:MaxbEtheneHOMO.jpg|250px]]
| align="center"|[[File:MaxBEtheneLUMO.jpg|250px]]
|}
[[Media:ETHENEOPTMAXB.LOG]]
[[Media:BUTADIENEOPTMAXB.LOG]]
 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ Molecular Orbitals of the Transition State
|-
| style="text-align: center;"|MO 16 of TS
| style="text-align: center;"|HOMO of TS
| style="text-align: center;"|LUMO of TS
| style="text-align: center;"|MO 19 of TS
|-
| align="center"|[[File:MaxbTSMO16.jpg|250px]]
| align="center"|[[File:MaxbTSHOMO.jpg|250px]]
| align="center"|[[File:MaxbTSLUMO.jpg|250px]]
| align="center"|[[File:MaxbTSMO19.jpg|250px]]
|}
[[Media:BUTAANDETHANETS.LOG]]

 

The HOMO of the ethylene and the LUMO of the butadiene are both of gerade symmetry so they interact to produce molecular orbitals shown above. The HOMO of the butadiene and the LUMO of the ethylene are both of ungerade symmetry so they interact to give molecular orbital shown above. This follows a typical Diels-Alder reaction as the HOMO of butadiene is of higher energy than the HOMO of the ethylene.

===Bond Length Analysis===

{| class="wikitable" style="margin: 1em auto 1em auto;"
! rowspan="2" style="text-align: center;" | Carbon Bonds
! colspan="3" style="text-align: center;" | Bond Length (Å)
|-
| style="text-align: center;" | Reactants
| style="text-align: center;" | Transition State
| style="text-align: center;" | Product
|-
| C1-C2
| style="text-align: center;" | 1.33528
| style="text-align: center;" | 1.37980
| style="text-align: center;" | 1.50090
|-
| C2-C3
| style="text-align: center;" | 1.46837
| style="text-align: center;" | 1.41112
| style="text-align: center;" | 1.33784
|-
| C3-C4
| style="text-align: center;" | 1.33528
| style="text-align: center;" | 1.37979
| style="text-align: center;" | 1.50090
|-
| C4-C5
| style="text-align: center;" | n/a
| style="text-align: center;" | 2.11464
| style="text-align: center;" | 1.54040
|-
| C5-C6
| style="text-align: center;" | 1.32741
| style="text-align: center;" | 1.38177
| style="text-align: center;" | 1.54091
|-
| C6-C1
| style="text-align: center;" | n/a
| style="text-align: center;" | 2.11482
| style="text-align: center;" | 1.54040
|}

==='''Transition State'''===
 

[[File:ButaEthaneTSMB.gif|center]]
[[MediaːBUTAANDETHANETS.LOG]]

 

The above vibration shows that the new C-C bonds form synchronously as the C-C bond of the butadiene is compressed whilst the terminal carbon atoms of each reactant move closer together simultaneously.

==='''Reaction Path'''===

==Exercise 2ː Reaction of Cyclohexadiene and 1,3-Dioxole==

 

[[File:MaxBScheme2.jpg]]
 

The reactants, transition states and the exo- and endo- adducts of the product were optimized to the B3LYP/6-31G(d) level on Gaussian.

 

==='''Molecular Orbital Analysis'''===

 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO of Cyclohexadiene and 1,3-Dioxole
|-
| style="text-align: center;"|HOMO of Cyclohexadiene
| style="text-align: center;"|LUMO of Cyclohexadiene
| style="text-align: center;"|HOMO of 1,3-Dioxole
| style="text-align: center;"|LUMO of 1,3-Dioxole
|-
| align="center"|[[File:MaxbButadieneHOMO.jpg|250px]]
| align="center"|[[File:MaxbHEXALUMO.jpg|250px]]
| align="center"|[[File:MaxbOXYHOMO.jpg|250px]]
| align="center"|[[File:MaxbOXYLUMO.jpg|250px]]
|}
[[Media:CYCLOOXYGEN2.LOG]]
[[Media:CYCLOHEXADIENEDFTMAXB.LOG]]

 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO Endo- and Exo- Trasition States
|-
| style="text-align: center;"|HOMO of EXO-
| style="text-align: center;"|LUMO of EXO-
| style="text-align: center;"|HOMO of ENDO-
| style="text-align: center;"|LUMO of ENDO-
|-
| align="center"|[[File:MaxbEXOHOMO.jpg|250px]]
| align="center"|[[File:MaxBEXOLUMO.jpg|250px]]
| align="center"|[[File:MaxbENDOHOMO.jpg|250px]]
| align="center"|[[File:MaxbENDOLUMO.jpg|250px]]
|}

[[Media:REACTANTS TS B3LPY.LOG]]
[[Media:REACTANTS ENDO TS B3LPY.LOG]]

 

This reaction is between an electron rich dienophile (Cyclohexadiene) and an electron-poor diene (1,3-Dioxole) meaning that an inverse electron demand Diels-Alder reaction occurs. The main difference between the molecular orbitals in an inverse and a standard Diels-Alder reaction is that in an inverse reaction the HOMO of the diene is lower in energy than the LUMO of the Dienophile.

==='''Thermochemistry'''===
 

{| class="wikitable" style="margin: 1em auto 1em auto;"
! style="font-weight: bold;" |
! style="font-weight: bold;" | Reactants
! style="font-weight: bold;" | Transition State
! style="font-weight: bold;" | Product
! style="font-weight: bold;" | Ea
! style="font-weight: bold;" | ΔGr
|-
| Exo
| -500.389165
| -500.329168
| -500.417323
| 0.060
| 0.028
|-
| Endo
| -500.389165
| -500.332111
| -500.418691
| 0.057
| 0.030
|}

<br/ v>

The endo product is shown here to have both a lower activation energy and a large change in gibbs energy meaning that it is both the kinetic and thermodynamic product.
This is because in the endo product the p-orbitals on the oxygen of the 1,3-dioxole are interacting with the pi orbitals of the new carbon-carbon double bond resulting in a stabilised transition state. Furthermore there is steric hinderance in the exo transition state between the two oxygen atoms and ethane bridge.

==Exercise 3: Diels-Alder vs Cheletropic==

 

[[File:MaxbReactionScheme3.jpg|centre]]

Rep:Mod:MaxBridge

2017-03-11T16:37:10Z

Mhb314: /* Thermochemistry */

== '''Introduction''' ==

A potential energy surface (PES) is used to show the energy of a system as a function pof the positions of the atoms in that system.
A PES can be used to determine whether a transition state occurs during a reaction, in which a species is made that is different to the reactants and the products. When evaluating the stationary points on a PES, ie when the gradient is zero, it is found that the minima points are where the reactants and products are located and the maxima occurs when a transition state occurs. To confirm where the minima and maxima are the second derivative is taken and are found to be postive and negative respectively. Furthermore through using gaussian it can be shown that a transition sate will a negative frequency and the reactants and products will not.

During this report there will be three different exercises explored using Gaussian in which the reactants, products and transition states were all optimised at the PM6 level along with frequency calculations also performed. For exercise 2 the products were also ran at the B3LYP/6-31(d) level. An IRC calculation was ran for every reaction in order to show the reaction coordinate.

== Exercise 1: Reaction of Butadiene with Ethylene ==

[[File:Reaction scheme.jpg]]

This reaction has been analyzed by optimizing the reactants and transition state using Gaussian at the PM6 level. The presence of a transition state was confirmed by running a frequency calculation at the PM6 level of the transition state and a negative frequency of -948.80 being shown.

==='''Molecular Orbital Analysis'''===

[[File:MaxbMODiagram.jpg]]

The molecular orbital diagram shows the HOMO and LUMO of both reactants and the transition state.

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO of Butadiene and Ethylene
|-
| style="text-align: center;"|HOMO of Butadiene
| style="text-align: center;"|LUMO of Butadiene
| style="text-align: center;"|HOMO of Ethylene
| style="text-align: center;"|LUMO of Ethylene
|-
| align="center"|[[File:MaxbButadieneHOMO.jpg|250px]]
| align="center"|[[File:MaxbButadieneLUMO.jpg|250px]]
| align="center"|[[File:MaxbEtheneHOMO.jpg|250px]]
| align="center"|[[File:MaxBEtheneLUMO.jpg|250px]]
|}
[[Media:ETHENEOPTMAXB.LOG]]
[[Media:BUTADIENEOPTMAXB.LOG]]
 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ Molecular Orbitals of the Transition State
|-
| style="text-align: center;"|MO 16 of TS
| style="text-align: center;"|HOMO of TS
| style="text-align: center;"|LUMO of TS
| style="text-align: center;"|MO 19 of TS
|-
| align="center"|[[File:MaxbTSMO16.jpg|250px]]
| align="center"|[[File:MaxbTSHOMO.jpg|250px]]
| align="center"|[[File:MaxbTSLUMO.jpg|250px]]
| align="center"|[[File:MaxbTSMO19.jpg|250px]]
|}
[[Media:BUTAANDETHANETS.LOG]]

 

The HOMO of the ethylene and the LUMO of the butadiene are both of gerade symmetry so they interact to produce molecular orbitals shown above. The HOMO of the butadiene and the LUMO of the ethylene are both of ungerade symmetry so they interact to give molecular orbital shown above. This follows a typical Diels-Alder reaction as the HOMO of butadiene is of higher energy than the HOMO of the ethylene.

===Bond Length Analysis===

{| class="wikitable" style="margin: 1em auto 1em auto;"
! rowspan="2" style="text-align: center;" | Carbon Bonds
! colspan="3" style="text-align: center;" | Bond Length (Å)
|-
| style="text-align: center;" | Reactants
| style="text-align: center;" | Transition State
| style="text-align: center;" | Product
|-
| C1-C2
| style="text-align: center;" | 1.33528
| style="text-align: center;" | 1.37980
| style="text-align: center;" | 1.50090
|-
| C2-C3
| style="text-align: center;" | 1.46837
| style="text-align: center;" | 1.41112
| style="text-align: center;" | 1.33784
|-
| C3-C4
| style="text-align: center;" | 1.33528
| style="text-align: center;" | 1.37979
| style="text-align: center;" | 1.50090
|-
| C4-C5
| style="text-align: center;" | n/a
| style="text-align: center;" | 2.11464
| style="text-align: center;" | 1.54040
|-
| C5-C6
| style="text-align: center;" | 1.32741
| style="text-align: center;" | 1.38177
| style="text-align: center;" | 1.54091
|-
| C6-C1
| style="text-align: center;" | n/a
| style="text-align: center;" | 2.11482
| style="text-align: center;" | 1.54040
|}

==='''Transition State'''===
 

[[File:ButaEthaneTSMB.gif|center]]
[[MediaːBUTAANDETHANETS.LOG]]

 

The above vibration shows that the new C-C bonds form synchronously as the C-C bond of the butadiene is compressed whilst the terminal carbon atoms of each reactant move closer together simultaneously.

==='''Reaction Path'''===

==Exercise 2ː Reaction of Cyclohexadiene and 1,3-Dioxole==

 

[[File:MaxBScheme2.jpg]]
 

The reactants, transition states and the exo- and endo- adducts of the product were optimized to the B3LYP/6-31G(d) level on Gaussian.

 

==='''Molecular Orbital Analysis'''===

 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO of Cyclohexadiene and 1,3-Dioxole
|-
| style="text-align: center;"|HOMO of Cyclohexadiene
| style="text-align: center;"|LUMO of Cyclohexadiene
| style="text-align: center;"|HOMO of 1,3-Dioxole
| style="text-align: center;"|LUMO of 1,3-Dioxole
|-
| align="center"|[[File:MaxbButadieneHOMO.jpg|250px]]
| align="center"|[[File:MaxbHEXALUMO.jpg|250px]]
| align="center"|[[File:MaxbOXYHOMO.jpg|250px]]
| align="center"|[[File:MaxbOXYLUMO.jpg|250px]]
|}
[[Media:CYCLOOXYGEN2.LOG]]
[[Media:CYCLOHEXADIENEDFTMAXB.LOG]]

 

{| class="wikitable" style="border: 1px solid black; margin: 1em auto;"
|+ HOMO and LUMO Endo- and Exo- Trasition States
|-
| style="text-align: center;"|HOMO of EXO-
| style="text-align: center;"|LUMO of EXO-
| style="text-align: center;"|HOMO of ENDO-
| style="text-align: center;"|LUMO of ENDO-
|-
| align="center"|[[File:MaxbEXOHOMO.jpg|250px]]
| align="center"|[[File:MaxBEXOLUMO.jpg|250px]]
| align="center"|[[File:MaxbENDOHOMO.jpg|250px]]
| align="center"|[[File:MaxbENDOLUMO.jpg|250px]]
|}

[[Media:REACTANTS TS B3LPY.LOG]]
[[Media:REACTANTS ENDO TS B3LPY.LOG]]

 

This reaction is between an electron rich dienophile (Cyclohexadiene) and an electron-poor diene (1,3-Dioxole) meaning that an inverse electron demand Diels-Alder reaction occurs. The main difference between the molecular orbitals in an inverse and a standard Diels-Alder reaction is that in an inverse reaction the HOMO of the diene is lower in energy than the LUMO of the Dienophile.

==='''Thermochemistry'''===
 

{| class="wikitable" style="margin: 1em auto 1em auto;"
! style="font-weight: bold;" |
! style="font-weight: bold;" | Reactants
! style="font-weight: bold;" | Transition State
! style="font-weight: bold;" | Product
! style="font-weight: bold;" | Ea
! style="font-weight: bold;" | ΔGr
|-
| Exo
| -500.389165
| -500.329168
| -500.417323
| 0.060
| 0.028
|-
| Endo
| -500.389165
| -500.332111
| -500.418691
| 0.057
| 0.030
|}

<br/ v>

The endo product is shown here to have both a lower activation energy and a large change in gibbs energy meaning that it is both the kinetic and thermodynamic product.
This is because in the endo product the p-orbitals on the oxygen of the 1,3-dioxole are interacting with the pi orbitals of the new carbon-carbon double bond resulting in a stabilised transition state. Furthermore there is steric hinderance in the exo transition state between the two oxygen atoms and ethane bridge.

==Exercise 3: Diels-Alder vs Cheletropic==

 

[[File:MaxbReactionScheme3.jpg|centre]]

Rep:Mod:MaxBridge

2017-03-11T16:08:53Z

Mhb314: /* Molecular Orbital Analysis */

Rep:Mod:MaxBridge

2017-03-11T15:44:03Z

Mhb314: /* Molecular Orbital Analysis */

File:REACTANTS ENDO TS B3LPY.LOG

2017-03-11T15:43:27Z

Mhb314:

File:REACTANTS TS B3LPY.LOG

2017-03-11T15:43:14Z

Mhb314:

Rep:Mod:MaxBridge

2017-03-11T15:41:19Z

Mhb314: /* Molecular Orbital Analysis */

File:MaxbENDOHOMO.jpg

2017-03-11T15:38:09Z

Mhb314:

File:MaxbENDOLUMO.jpg

2017-03-11T15:37:59Z

Mhb314:

File:MaxbEXOHOMO.jpg

2017-03-11T15:37:43Z

Mhb314:

File:MaxBEXOLUMO.jpg

2017-03-11T15:37:25Z

Mhb314:

Rep:Mod:MaxBridge

2017-03-11T15:25:30Z

Mhb314: /* Molecular Orbital Analysis */

File:CYCLOHEXADIENEDFTMAXB.LOG

2017-03-11T15:25:07Z

Mhb314:

File:CYCLOOXYGEN2.LOG

2017-03-11T15:24:07Z

Mhb314:

Rep:Mod:MaxBridge

2017-03-11T15:20:21Z

Mhb314: /* Exercise 2ː Reaction of Cyclohexadiene and 1,3-Dioxole */

File:MaxbOXYLUMO.jpg

2017-03-11T15:20:12Z

Mhb314:

File:MaxbOXYHOMO.jpg

2017-03-11T15:19:58Z

Mhb314:

File:MaxbHEXALUMO.jpg

2017-03-11T15:19:44Z

Mhb314:

File:MaxbHEXAHOMO.jpg

2017-03-11T15:19:23Z

Mhb314:

Rep:Mod:MaxBridge

2017-03-11T14:32:48Z

Mhb314: /* Transition State */

Rep:Mod:MaxBridge

2017-03-11T14:24:30Z

Mhb314: /* Molecular Orbital Analysis */

Rep:Mod:MaxBridge

2017-03-11T14:18:17Z

Mhb314: /* Molecular Orbital Analysis */

File:BUTADIENEOPTMAXB.LOG

2017-03-11T14:14:23Z

Mhb314:

File:ETHENEOPTMAXB.LOG

2017-03-11T14:14:09Z

Mhb314:

File:MaxbTSHOMO.jpg

2017-03-11T14:07:22Z

Mhb314:

File:MaxbTSLUMO.jpg

2017-03-11T14:07:05Z

Mhb314:

File:MaxbTSMO19.jpg

2017-03-11T14:06:39Z

Mhb314:

File:MaxbTSMO16.jpg

2017-03-11T14:06:22Z

Mhb314:

Rep:Mod:MaxBridge

2017-03-11T13:57:05Z

Mhb314: /* Molecular Orbital Diagram */

File:MaxbButadieneHOMO.jpg

2017-03-11T13:52:02Z

Mhb314: