Modlec4918

Molecules

NH₃

	Values
Calculation Method	RB3LYP
Basis Set	6-31G(d.p)
Final Energy E(RB3LYP)	-56.55776873 a.u.
RMS gradient	0.00000485
Point group	C3v
N-H bond length	1.018 Ångström
H-N-H bond angle	105.7 degrees

Text File

         Item               Value     Threshold  Converged?
 Maximum Force            0.000004     0.000450     YES
 RMS     Force            0.000004     0.000300     YES
 Maximum Displacement     0.000072     0.001800     YES
 RMS     Displacement     0.000035     0.001200     YES

NH3

Display Vibrations

NH₃

Wavenumber cm-1	1089.5366	1693.9474	1693.9474
Symmetry	A1	E	E
Intensity a.u.	145.3814	13.5533	13.5533
Image
Wavenumber cm-1	3589.8170	3589.8170	3461.2932
Symmetry	E	E	A1
Intensity a.u.	0.2711	0.2711	1.0608
Image

The number of modes of NH₃ expected using 3N-6 rule is 6, as N=4. There are two degenerate energy levels at 1693cm^-1 and 3589cm^-1. On an IR spectrum of gaseous ammonia only two bands at frequencies, 1089cm^-1 and 1693cm^-1 are seen as only two vibrations result in a change in dipole, due to the unsymmetrical vibrations of the molecule. The 1089cm^-1 and 3460cm^-1 are symmetric, however 3460cm^-1 is highly symmetric as even as the vibrations change the point group remains the same. The bending modes are 1089cm^-1 , 1693cm^-1 and the stretching 3589cm^-1 , 3461cm^-1. The bending mode of 1089cm^-1 is known as the umbrella mode due the shape of the vibrations made.

Charge

Atom	Charge
N	-1.125
H	0.375

The nitrogen in ammonia is electronegative and therefore draws the electrons in the hydroigen bonds towards itself. If the charge on the nitrogen is -1 then the overal charge of the bonded hydrogens is +1 split 3 ways which is +0.333.

Nitrogen

N₂

	Values
Calculation Method	RB3LYP
Basis Set	6-31G(d.p)
Final Energy E(RB3LYP)	-109.52412868 a.u.
RMS gradient	0.00000060 a.u.
Point group	D*H
N-N bond length	1.11 Ångström

         Item               Value     Threshold  Converged?
 Maximum Force            0.000001     0.000450     YES
 RMS     Force            0.000001     0.000300     YES
 Maximum Displacement     0.000000     0.001800     YES
 RMS     Displacement     0.000000     0.001200     YES
 Predicted change in Energy=-3.401072D-13

N2

Display Vibrations

N₂

Wavenumber cm-1	2457.3283
Symmetry	SGG
Intensity a.u.	0.0000
Image

An IR spectrum run on gaseous nitrogen produces no bands as it has only one vibrational mode at 2457cm^-1 and this vibrational mode is symmetrical and does not result in a change of dipole moments required to produce a band on IR spectrum.

Charge

Atom	Charge
N	0.000

Hydrogen

H₂

	Values
Calculation Method	RB3LYP
Basis Set	6-31G(d.p)
Final Energy E(RB3LYP)	- 1.17853936 a.u.
RMS gradient	0.00000017 a.u.
Point group	D*H
H-H bond length	0.74 Ångström

         Item               Value     Threshold  Converged?
 Maximum Force            0.000000     0.000450     YES
 RMS     Force            0.000000     0.000300     YES
 Maximum Displacement     0.000000     0.001800     YES
 RMS     Displacement     0.000001     0.001200     YES
 Predicted change in Energy=-1.164080D-13

H2

Display Vibrations

N₂

Wavenumber cm-1	4465.6824
Symmetry	SGG
Intensity a.u.	0.0000
Image

An IR spectrum run on gaseous Hydrogen produces no bands as it has only one vibrational mode at 4465cm^-1 and this vibrational mode is symmetrical and does not result in a change of dipole moments required to produce a band on IR spectrum.

Charge

Atom	Charge
H	0.000

NF₃

N₂

	Values
Calculation Method	RB3LYP
Basis Set	6-31G(d.p)
Final Energy E(RB3LYP)	-354.0713058 a.u.
RMS gradient	0.00010256 a.u.
Point group	C3v
N-F bond length	1.38 Ångström
N-N bond angle	101.8 degrees

Item               Value     Threshold  Converged?
 Maximum Force            0.000164     0.000450     YES
 RMS     Force            0.000108     0.000300     YES
 Maximum Displacement     0.000612     0.001800     YES
 RMS     Displacement     0.000296     0.001200     YES
 Predicted change in Energy=-1.274066D-07

N2

Display Vibrations

N₂

Wavenumber cm-1	644.1656	482.1544	482.1554
Symmetry	A1	E	E
Intensity a.u.	2.7521	0.5246	0.5246
Image
Wavenumber cm-1	1062.3189	929.7696	929.7719
Symmetry	A1	E	E
Intensity a.u.	39.9238	208.0734	208.0734
Image

NF₃ has 6 vibrational modes. There are two sets of degenerate energy levels, one at 482.15 cm^-1 and 929.77cm^-1. An IR spectrum run on gaseous NF₃ produces two bands, a peak at 929.77cm^-1 and 1062.32cm^-1, these peaks are visible as the movements result in a change in dipole moments required for a bond vibration to been seen on an IR spectrum.

Charge

Atom	Charge
N	0.660
F	-0.220

Molecular Orbitals NF₃

NF₃

MO Number	1	5	10
Image
Comment	This shows three Fluorine 1s atomic orbitals that are not involved in bonding of the atoms as they are in the lowest energy states, and the charge density is concentrated around the Fluorine atoms. It has an energy of -24.76570 a.u.	This shows the molecular bonding orbitals of NF3 due to an overlap of 1s orbitals throughout the structure, this means there have a slightly higher energy of -1.35870 a.u. and the charge density is spread out across the molecule.	This shows the overlap 2p orbitals of the central Nitrogen atom and one fluorine atom. The other two fluorine atoms are not involved in bonding As the 2p oribtals are in higher energy the overall energy is slightly higher at -0.61981 a.u.
MO Number	16	20
Image
Comment	This molecular orbital is a non-bonding orbital as there is no overlap of orbitals. The orbitals shown are 2p orbitals of the fluorine atoms. The nodes around the fluorine atoms show that they are non-bonding orbitals. This has a slightly higher energy at -0.42224 a.u.	This molecular oribital shows the anti-bonding orbitals of the atoms in NF3 it is indicated by the nodes between the nitrogen and fluorine atoms. This has the a higher energy at +0.02263 a.u.

N₂ as a Ligand

Charge

Structural identifier	VEJSOV
N-N bond length	1.12
Link to Structure	[[1]]

The bond length in the metal ion complex is longer then the experimental. This is for a number of reasons, such as in the computational method the nitrogen is bonded to a metal ion, this will draw electron density away from the nitrogen atom and weaken the bond this is turn lengthens the bond. Another reason is that the computational method measures the bond length when the molecule is in the gaseous phase whereas the experimental is measured in the solid state.

H₂ as a Ligand

Charge

Structural identifier	BIDQUB
H-H bond length	0.91
Link to Structure	[[2]]

Haber-Bosch Process

ΔE=2*E(NH₃)-[E(N₂)+3*E(H₂)]

Haber-Bosch Process

Molecule	Energy (a.u)
NH3	-56.5577687
2*NH3	-113.1155374
N2	-109.5241286
H2	- 1.1785393
3*H2	-3.5356180
ΔE	-0.0557907
ΔE (in kJ/mol)	-146.47849401

The product is more stable then the reactant as the change in energy is negative.

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 received your grade from blackboard.

Wiki structure and presentation 0.5/1

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

YES

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

You have used figures and headings however your whole wiki is under the heading "molecules" and you have a subheading called "Text file", these headings don't help the reader.

NH3 0/1

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

No you have not linked to the file. (I know it is included in the jmol but the labscript asks for 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?

YES

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 - unfortunately you have not linked directly to the log files again.

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

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?

No - you should have rounded to 1 or 0.1 kJmol-1, not 8 d.p!

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?

YES

Your choice of small molecule 2.5/5

Have you completed the calculation and included all relevant information?

YES - however you forgot to link the log file.

Have you added information about MOs and charges on atoms?

YES - good information on the vibrations, and good comment on MO 20, well done! However some of your other MO explanations are not correct, for example MO 5 is the in-phase combination of 2s AOs from all the atoms, not 1s.

Independence 1/1

If you have finished everything else and have spare time in the lab you could: Check one of your results against the literature, or

YES - you have looked up a h2 containing complex in the literature, well done.

Do an extra calculation on another small molecule, or Do some deeper analysis on your results so far