01532430

NH₃

test molecule

NH3 Item Section

NH3 Frequency Vibrations

More Info
N-H Bond Distance:	1.01798Å
H-N-H Bond Angle:	105.741°
Calculation Method:	RB3LYP
Basis Set:	6-31G(d,p)
Final Energy:	-56.55776873
RMS gradient:	0.00000485
Point Group	C3V

Symmetry of Vibrations

Symmetry	A1	E
Wavenumber (cm-1)	3461	3590
Intensity	145	14

Charges on Atoms

Charge on each atom: Nitrogen=-1.125, Hydrogen=0.375

Questions:

1) how many modes do you expect from the 3N-6 rule? 6

2) which modes are degenerate (ie have the same energy? Modes 2 and 3, Modes 5 and 6, are degenerate

3) which modes are "bending" vibrations and which are "bond stretch" vibrations? 1,2,3 are bond vibrations while 4,5,6 are bond stretches

4) which mode is highly symmetric? 4

5) one mode is known as the "umbrella" mode, which one is this? 1

6) how many bands would you expect to see in an experimental spectrum of gaseous ammonia? 4

N₂

test molecule

N2 Item Section

N2 Frequency Vibrations

More Info
N-N Triple bond distance:	1.10550
Calculation Method	RB3LYP
Basis Set	6-31G(d.p)
Final Energy	-109.52412868
RMS gradient	0.00000060
Point Group	D*H

Symmetry of Vibrations

Symmetry	SGG
Wavenumber (cm-1)	2457
Intensity	0

H₂

test molecule

H2 Item Section

H2 Frequency Vibrations

More Info
H-H Bond Distance	0.74279
Calculation Method	RB3LYP
Basis Set	6-31G(d.p)
Final Energy	-1.17853936
RMS gradient	0.00000017
Point Group	D*H

Symmetry of Vibrations

Symmetry	SGG
Wavenumber (cm-1)	4466
Intensity	0

Haber-Bosch Process

Measured in a.u.

• E(NH₃)= -56.55777
• 2*E(NH₃)= -113.11554
• E(N₂)= -109.52413
• E(H₂)= -1.17854
• 3*E(H₂)= -3.53562
• ΔE=2*E(NH₃)-[E(N₂)+3*E(H₂)]= -0.05579a.u = -146KJmol^-1

Mono-metallic TM Complex

test molecule

CCDC Unique Identifier: KECVUJ

H-H Bond length of TM complex: 0.814577

H-H Bond length of hydrogen molecule: 0.74279

The above structure reported by Ricci et al. //place

Q. Why are the bond lengths different?

A. The method of working out the bond length is RB3LYP. This method is not the most sophisticated and so will lead to a potentially inaccurate bond length. Not only is the method not highly complex but the hardware being used isn't powerful enough to carry out the calculations required to find an accurate value of either bond length. Despite this for both bond length calculations, the same method was used. Therefore, using the RB3LYP method, within this complex, the hydrogen bond is longer then that of the bond of the hydrogen molecule. This is due to the electrons in the HOMO bonding orbital of the hydrogen molecule bonding to the d orbital of the metal complex, as well as some of the electron density now being in the LOMO orbital of the hydrogen MO. This overall makes the bond between the hydrogen atoms weaker which is shown by the longer bond.

SH₂

test molecule

SH2 Item Section

SH2 Frequency Vibrations

More Info
S-H Bond Distance	1.31000
H-S-H Bond Angle	92.250
Calculation Method	RB3LYP
Basis Set	6-31G(d.p)
Final Energy	-399.39162414
RMS gradient	0.00012068
Point Group	C2V

Symmetry of Vibrations

Symmetry	A1	A1
Wavenumber (cm-1)	1224	2692
Intensity	4.922	6.735

Molecular Orbitals of SH₂

Molecular Orbital	2	3	9	6	11
Description	MO showing bonding 1s AO. This orbital is deep in energy, -7.95, therefore showing little to no overlap, and so little chemical bonding interaction	MO 3 shows the valence electrons present in the S 2s AO. This is shown by the mixture of bonding and antibonding surrounding the S atom	This shows the 3p AO of the S atom. As shown by the high energy of the orbital, -0.25, there is an overlap of the 3p AO and 1s orbital of hydrogen.	The energy of this MO is high, -0.75, further showing the huge overlap between the S 3s AO and 1s H AO.	High overlap of 3p S orbital and H 1s orbital.. The 3p S has a mixture of bonding and antibonding orbitals. Here the difference in energy between the Bonding and antibonding is large, 0.057, which help explain the high overlap of the Atomic Orbitals.

Marking

Note: All grades and comments are provisional and subject to change until your grades are officially returned via blackboard. Please do not contact anyone about anything to do with the marking of this lab until you have recieved your grade from blackboard.

Wiki structure and presentation 0.5/1

Is your wiki page clear and easy to follow, with consistent formatting?

YES overall it looks good well done!

Do you effectively use tables, figures and subheadings to communicate your work?

YES however you have left the caption for your jmols as "test molecule" for all of them. Also just one of your subheadings is bold for some reason which is inconsistent and confusing to a reader. "Measured in a.u." is also not a useful subheading!

NH3 0/1

Have you completed the calculation and given a link to the file?

NO - there is no link to the file present. (It is included in the jmol but this does not count as a direct link.)

Have you included summary and item tables in your wiki?

YES

Have you included a 3d jmol file or an image of the finished structure?

YES

Have you included the bond lengths and angles asked for?

YES

Have you included the “display vibrations” table?

YES

Have you added a table to your wiki listing the wavenumber and intensity of each vibration?

YES

Did you do the optional extra of adding images of the vibrations?

YES

Have you included answers to the questions about vibrations and charges in the lab script?

The correct charges are present and you have correctly answered most of the questions on the vibrations, well done! However you would expect only 2 visible peaks in the spectrum as peaks 4, 5 and 6 are very low in intensity.

N2 and H2 0/0.5

Have you completed the calculations and included all relevant information? (summary, item table, structural information, jmol image, vibrations and charges)

YES

There is no link to the files present. (It is included in the jmol but this does not count as a direct link.)

Crystal structure comparison 0.5/0.5

Have you included a link to a structure from the CCDC that includes a coordinated N2 or H2 molecule?

YES

Have you compared your optimised bond distance to the crystal structure bond distance?

YES - the section about the bonding between the complex and the H2 molecule is very good well done!

Haber-Bosch reaction energy calculation 0.5/1

Have you correctly calculated the energies asked for? ΔE=2*E(NH3)-[E(N2)+3*E(H2)]

YES

Have you reported your answers to the correct number of decimal places?

YES

Do your energies have the correct +/- sign?

YES

Have you answered the question, Identify which is more stable the gaseous reactants or the ammonia product?

No - you didn't remember to answer the question.

Your choice of small molecule 2/5

Have you completed the calculation and included all relevant information?

YES There is no link to the files present. (It is included in the jmol but this does not count as a direct link.)

Have you added information about MOs and charges on atoms?

You haven't included any information on the charges.

You have included pictures of several relevant MOs in a nicely presented table - well done!

The description of MO2 is correct.

MO3 is one of the three S 2p AOs.

MO9 is the one of the 3 S 3p AOs, there is no overlap with the H 1s AOs.

MO6 is S 3s and H 1s bonding, you are correct. It has a low energy, not a high energy.

MO11 looks like S 3s and H 1s anti bonding. There is no S 3p AO here.

Independence 0/1

If you have finished everything else and have spare time in the lab you could: Check one of your results against the literature, or Do an extra calculation on another small molecule, or Do some deeper analysis on your results so far

You didn't do any extra work for the independence mark.