Force field calculations of methanol and evaluation of the effect of ions on its stretching vibrations

Abstract

Redundancy-free internal valence force field for methanol was evaluated using CNDO/Force calculations and least-squares refinement. The initial force field was set up by taking the interaction and bending force constants from CNDO force field and transferring stretching force constants from the force fields of chemically related molecules. Vibrational frequencies of CH 3OH, CH 3OD, CD 3OH, CD 3OD, SCH 2DOH, SCH 2DOD, SCHD 2OH and SCHD 2OD are used to refine the force constants. The final force field thus obtained was found to be reasonable on the basis of the frequency fit and the potential energy distribution. The effects of cation—molecule and anion—molecule interactions on the stretching force constants of methanol are discussed using CNDO/Force method.