Infrared and Raman Spectra of Methyl Thiocyanate and Methyl Isothiocyanate

Infrared spectra are reported for CH3SCN and CH3NCS from 170–3100 cm−1 for both liquid and vapor states. The Raman spectrum of CH3NCS has been re‐determined. A vibrational assignment is suggested for each molecule which is complete except for the methyl torsional frequencies. A useful qualitative means of distinguishing organic thiocyanates from isothiocyanates is the infrared absorption near 2150 cm−1. In thiocyanates this is a strong, relatively sharp band, whereas in isothiocyanates it is a strong, very broad absorption which is usually resolvable into 2–3 maxima. The origins of the latter are discussed.