Remarks on the Interpretation of the CH2 Vibrational Frequencies of n-Paraffins

The infrared and Raman frequencies are calculated for the fundamental vibrations of an infinite n-paraffin chain. Valence force constants, chosen to give agreement between the calculated and observed infrared frequencies, give calculated Raman frequencies which are correlated with observed Raman lines. The difference in frequency to be expected for the Raman and infrared bands of the CH2 out-of-plane rocking vibration is discussed. The CH2 frequencies of propane are calculated from the infinite paraffin chain force constants and are compared with previous assignments.