Rep:Mod:WSX4567
NH3
Molecule: Ammonia
Calculation Method: RB3LYP
Basis Set: 6-31G(d.p.)
Final energy: -56.55776873 au
RMS Gradient: 0.00000485 au
Point Group: C3v
Optimised bond distance: 1.04 Å
Optimised bond angle: 106°
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 |
The optimisation file is linked to here
| Wavenumber cm-1 | 1090 | 1694 | 1694 | 3641 | 3590 | 3590 |
| Symmetry | A1 | E | E | A1 | E | E |
| Intensity arbitrary units | 145 | 14 | 14 | 1 | 0 | 0 |
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| Vibrational mode type: | Bending (Umbrella) | Bending | Bending | Highly Symmetric Stretch | Stretch | Stretch |
Expected modes of vibration:(3x4)-6=6
Degenerate modes: 1694&1694(cm-1), and 3590&3590(cm-1)
Spectrum bands: 4
Charges
Expected charges would be negative on nitrogen and positive on hydrogen as nitrogen is more electronegative than hydrogen so the electrons are pulled towards the nitrogen as greater effective nuclear charge.
H2
Molecule: Hydrogen
Calculation Method: RB3LYP
Basis Set: 6-31G(d.p.)
Final energy: -1.17853936 au
RMS Gradient: -0.00000017 au
Point Group: D∞h
Optimised bond distance: 0.74 Å
Optimised bond angle: -
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
H2 |
The optimisation file is linked to here
| Wavenumber cm-1 | 4466 |
| Intensity arbitrary units | 0 |
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| Vibrational mode type: | Symmetrical stretch |
Charge distribution H2
Both atoms of equal electronegativity so no charge, perfectly covalent.
N2
Molecule: Nitrogen
Calculation Method: RB3LYP
Basis Set: 6-31G(d.p.)
Final energy: -109.52412868 au
RMS Gradient: 0.00000077 au
Point Group: D∞h
Optimised bond distance: 1.11 Å
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 0.000001 0.001200 YES
N2 |
The optimisation file is linked to here
| Wavenumber cm-1 | 2457 |
| Intensity arbitrary units | 0 |
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| Vibrational mode type: | Symmetrical stretch |
Charge distribution N2
Both atoms of equal electronegativity so no charge, perfectly covalent.
Mono-metallic TM complex that coordinating N2
TM complex that coordinates N2 - https://www.ccdc.cam.ac.uk/structures/Search?Ccdcid=BALWUG&DatabaseToSearch=Published
.[1]
This Mono-metallic TM complex that coordinates N2 (name:μ2-Dinitrogen)-bis(dicarbonyl-bis(trimethylphosphite)-iron) has the unique identifier BALWUG and has a bond length of 1.13Å which is longer than the optimised bond length of 1.11Å. This could be because the iron surrounding the nitrogen withdraws electron density as it is a transition metal, so this will weaken the bond and therefore lengthen it. Or that in the computer programme when optimised it is in the gaseous state whereas it may not be when calculated otherwise which could effect the bond length.
Energy of reaction of NH3
E(NH3)= -56.5577687 au
2*E(NH3)= -113.11554 au
E(N2)= -109.5241287 au
E(H2)= -1.1785394 au
3*E(H2)= -3.53562 au
ΔE=2*E(NH3)-[E(N2)+3*E(H2)]= -0.05579 au (-146.47848 kj mol-1)
The energy change is negative and the ammonia product has lower energy than it's gaseous reactants so ammonia is therefore more stable than it's gaseous products.
CO
Molecule: Carbon Monoxide
Calculation Method: RB3LYP
Basis Set: 6-31G(d.p.)
Final energy: --113.30945314 au
RMS Gradient: 0.00001828 au
Point Group: C∞v
Optimised bond distance: 1.14 Å
Item Value Threshold Converged? Maximum Force 0.000032 0.000450 YES RMS Force 0.000032 0.000300 YES Maximum Displacement 0.000012 0.001800 YES RMS Displacement 0.000018 0.001200 YES
CO |
The optimisation file is linked to here
| Wavenumber cm-1 | 2209 |
| Intensity arbitrary units | 0 |
| Image | 
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| Vibrational mode type: | Symmetrical stretch |
Charge distribution of CO
As oxygen is more electronegative than carbon the electrons in the covalent bond will be closer to the oxygen, which is why the charge diagram agrees with what the charges should be. Negative on the oxygen and positive on the carbon.
Molecular orbitals
| Orbital type cm-1 | 2π* | 3σ | 1π | 1π | σ |
| Energy au | -0.02177 | -0.37145 | -0.46743 | -0.46743 | -19.25805 |
| Image | .png) |
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| Description: | This is the LUMO, lowest unoccupied molecular orbital, this is an anti-bonding orbital. | This is the HOMO, highest occupied molecular orbital, considerably lower in energy than the LUMO, this HOMO is a bonding orbital. The HOMO-LUMO gap determines the strength of interactions this energy gap for CO is -0.34968 au. | This is a pi orbital of which there are two, both degenerate with the same energy, both bonding orbitals. | This is the other pi orbital, of the same energy there are 2 electrons in each pi orbital they are both filled. | This is the lowest lying filled orbital with a significantly lower energy. This is so much lower in energy as is formed from the 1s atomic orbitals which are much lower lying and more tightly held to the nucleus. This is not involved in bonding at all as you can see, as no overlap. |
O2
Molecule: Oxygen
Calculation Method: RB3LYP
Basis Set: 6-31G(d.p.)
Final energy: -150.25742434 au
RMS Gradient: 0.00007502 au
Point Group: D∞h
Optimised bond distance: 1.22 Å
Item Value Threshold Converged? Maximum Force 0.000130 0.000450 YES RMS Force 0.000130 0.000300 YES Maximum Displacement 0.000080 0.001800 YES RMS Displacement 0.000113 0.001200 YES
O2 |
The optimisation file is linked to here
| Wavenumber cm-1 | 1643 |
| Intensity arbitrary units | 0 |
| Image | 
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| Vibrational mode type: | Symmetrical stretch |
Charge distribution of O2
Both atoms of equal electronegativity so no charge, perfectly covalent.
- ↑ H.Berke, W.Bankhardt, G.Huttner, J.von Seyerl, L.Zsolnai, Chemische Berichte, 1981, 114, 2754, DOI: 10.1002/cber.19811140809 .
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 1/1
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?
YES - but you could have used subheadings more efficiently.
NH3 0.5/1
Have you completed the calculation and given a link to the file?
YES
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 - You correctly stated two sets of degenerate modes which explains a spectrum with 4 bands. However, the stretching vibrations are too low in intensities to be observed in an experimental spectrum, so only 2 bands would be seen.
N2 and H2 0.5/0.5
Have you completed the calculations and included all relevant information? (summary, item table, structural information, jmol image, vibrations and charges)
YES
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 - You were asked to search for a monometallic TM complex but you stated a bimetallic one.
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 - the energy in kJ/mol should only be reported to one decimal place!
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
Have you completed the calculation and included all relevant information?
YES - but you missed to comment on the calculated vibrational mode at all.
Have you added information about MOs and charges on atoms?
You missed to comment on the occupancy of the orbitals and to explain the relative energies (e.g. number of nodes). You missed to include the contributing AOs except for the one lowest in energy. For some of the MOs you missed to describe their effect on bonding.
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 Do an extra calculation on another small molecule, or
YES - you could have eanalysed these results in more detail.
Do some deeper analysis on your results so far