return to home page Computational Chemistry Comparison and Benchmark DataBase Release 22 (May 2022) Standard Reference Database 101 National Institute of Standards and Technology
You are here: Comparisons > Vibrations > Vibrations

Compare vibrational frequencies in CCCBDB for CH3NO2 (Methane, nitro-)

BLYP/3-21G*

18 11 26 13 55
Frequency in cm-1
  Calculated   Experimental
Mode Number Symmetry Frequency Scaled
Frequency
Harm.
diff
Fund.
diff
Symmetry Harmonic
Frequency
Fundamental
Frequency
Comment
1 A' 3111 3091   46 A'   3045  
2 A' 3022 3003   29 A'   2974  
3 A' 1499 1489   92 A'   1397  
4 A' 1367 1358   -76 A'   1434  
5 A' 1121 1114   -266 A'   1380  
6 A' 1079 1072   -59 A'   1131  
7 A' 773 768   -150 A'   918  
8 A' 557 553   -104 A'   657  
9 A' 503 500   -103 A'   603  
10 A" 3146 3126   46 A"   3080  
11 A" 1498 1488   -95 A"   1583  
12 A" 1311 1302   -108 A"   1410  
13 A" 1026 1020   -76 A"   1096  
14 A" 404 401   -74 A"   475  
15 A" 24 24    A"     internal rotation, almost free rotor
The calculated vibrational frequencies were scaled by 0.9935
Nitromethane is essentially a free rotor. The calculations produce one of three conformations: 1) the NO2 plane perpendicular to a C-H bond, Cs symmetry; 2) The NO2 plane lined up with a C-H bond, Cs symmetry; 3) The NO2 plane at some small angle away from a C-H bond (C1 symmetry). Note that conformation 1 has 9 A' modes and 6 A" modes, conformation 2 has 10 A' modes and 5 A" modes, and conformation 3 has 15 A modes.

See section Calculated; Vibrations; Scale Factors; Set scaling factors to change the scale factors used here.
See section Calculated; Vibrations; Scale Factors; Calculate a scale factor to determine the least squares best scaling factor.
See section Calculated; Vibrations; Scale Factors; Scale factor uncertainty for information on where the above scaling factor is from.