Infrared Spectra and Normal Vibrations of <i>N</i>,<i>N</i>-Dimethylformamide and <i>N</i>,<i>N</i>-Dimethylthioformamide

Abstract

Abstract The infrared spectra of N,N-dimethylformamide (DMF) and N,N-dimethylthioformamide (DMTF) have been investigated in the range 4000–250 cm−1. Assignment of the frequencies of DMF has been made on the basis of normal coordinate analysis for DMF, DMF-15N, and DMF-d7 using Urey-Bradly, modified Urey-Bradley, and symmetrized valence force fields. Calculations have been extended to N,N-dimethylthioformamide and N,N-dimethylselenoformamide, using the Urey-Bradley and symmetrized valence force fields. The assignments for DMF from the modified Urey-Bradley field are found to be more satisfactory. The frequency shifts on isotopic substitution and on complexation have been explained. The results of the calculations are discussed in comparison with other related molecules.