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Methanol, CH3OH

Models were made using the best ab initio level of theory, which was 6311-G.  This is the best level because it is the biggest basis set for the molecule.  

Click below to view CH3OH bond lengths.  

methanol picture
Figure 1: CH3OH: (1)C, (2)O, (3)H, (4)H, (5)H, (6)H

Bond lengths of CH3OH were found using the Hamiltonians and three ab initio levels.  Bond lengths for atoms (1)C, (2)O, (3)H, (4)H, (5)H, (6)H in angstroms, Å, at the different levels of theory, see Figure 1.  Methanol had three literature bond lengths which were C-H 1.096 Å, C-O 1.427 Å, and O-H 0.956 Å.1
Atoms PM3 AM1 321-G 631-G 6311-G
1-2 1.394818 1.410427 1.440943 1.430507 1.428506
1-4 1.097026 1.118675 1.085102 1.083560 1.082426
1-5 1.093556 1.118997 1.078644 1.076815 1.075128
1-6 1.097016 1.118669 1.085122 1.083586 1.082428
2-3 0.948750  0.964087  0.965792 0.950207 0.946021


Click the button below to see CH3OH bond angles, H-C-H and H-O-C.
Click the button below to see CH3OH bond angles, O-C-H.
Bond angles for atoms (1)C, (2)O, (3)H, (4)H, (5)H, (6)H in degrees, °, at the different levels of theory, see Figure 1.  Methanol had experimental bond angles of H-C-H 109.03° and H-O-C 108.87°.1
Atoms PM3 AM1 321-G 631-G 6311-G
1-2-3 107.45 107.17 110.34 113.42 113.17
4-1-6 109.03 109.68 108.75 109.24 109.18
4-1-5 109.44 110.03 108.61 108.99 108.90
6-1-5 109.45 110.04 108.60 108.98 108.90
4-1-2 112.15 110.94 112.24 111.65 111.62
5-1-2 104.49 105.13 106.28 106.25 106.53
6-1-2 112.16 110.94 112.23 111.64 111.62

Click below to view the CH3OH HOMO orbital.   The HOMO orbital is the highest energy molecular orbital occupied by electrons.   From the model, it can be predicted how a molecule will react.   

Vibrational Frequencies
Click below to see the motion of the molecule at frequency 1116 cm-1. This contributes to ~1000 cm-1 peak in the IR spectrum. 2

Click below to see the motion of the molecule at frequency 1469 cm-1. This contributes to ~1400 cm-1 peak in the IR spectrum. 2
 
The next three frequencies contribute to the ~3000 cm-1 peak in the IR spectrum. 2 Click below to see the motion of the molecule at frequency 3156 cm-1
Click below to see the motion of the molecule at frequency 3211 cm-1
Click below to see the motion of the molecule at frequency 3305 cm-1

Click below to see the motion of the molecule at frequency 4043 cm-1. This contributes to ~3600 cm-1 peak in the IR spectrum. 2

Dipole moments at each level of theory for CH3OH.  Experimental 1.70 D.3
Theory Level Dipole (D)
PM3 1.621053
AM1 1.487285
321-G 2.121482
631-G 2.285451
6311-G 2.253251


References:
(1)  http://cccbdb.nist.gov/ .  Geometries. Experimental geometry data for a given species.  CH3OH.
(2)  http://webbook.nist.gov/. IR spectrum of CH3OH.
(3)  Lide, D. R. CRC Handbook of Chemistry and    Physics; CRC Press: Boca Raton, 1992.

HCl            Aniline
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