Substituted Methanes. VII. Vibrational Spectra, Force Constants, and Calculated Thermodynamic Properties for CH3I and CD3I

Abstract

Raman displacements for the liquid, and infrared absorption wave numbers for both liquid and gas, have been obtained for CH₃I, together with quantitative depolarization factors for the Raman lines and semiquantitative relative intensities for both the Raman and infrared bands. The present and previous data were critically compared, and probable values of the wave numbers corresponding to the fundamental vibrational frequencies were determined for both liquid and gaseous states. Force constants in a modified valence force potential function, containing all possible quadratic interaction constants, were calculated; these then were used to calculate the fundamentals of CD₃I. Finally, the heat content, free energy, entropy, and heat capacity for both CH₃I and CD₃I were calculated for 11 temperatures from 200° to 1000°K, for the ideal gaseous state at 1 atmos pressure.