Substituted Methanes. XXVIII. Infrared Spectral Data and Assignments for CHCl2F and CHClF2 and Potential Energy Constants and Calculated Thermodynamic Properties for CHCl2F, CDCl2F, CHClF2, and CDClF2

Abstract

Infrared spectral data were obtained with NaCl and CsBr prisms for gaseous CHCl2F and CHClF2 from 270 to 4000 K (K=kayser=wave/cm) and the observed absorption bands were assigned to the vibrational modes for both molecules. Using the Wilson FG matrix method, reasonable values of the F-matrix elements were found which reproduced the observed wave numbers to within 2%. These were then used to calculate the wave numbers corresponding to the fundamental vibrations of CDCl2F and CDClF2. Also, these F-matrix elements and analytical expressions obtained from the theory of Gold, Dowling, and Meister were used to get values of the f-matrix elements (potential energy constants). Having tested the assignments by the normal coordinate treatments, the observed wave numbers for CHCl2F and CHClF2 were then used to calculate the enthalpy function, the free energy function, the entropy, and the heat capacity for 1 atmos pressure and for 12 temperatures from 100 to 1000°K, to a rigid rotor, harmonic oscillator, ideal gas approximation. Since the calculated wave numbers for CDCl2F and CDClF2 should be reliable to within about 2%, these were used in similar thermodynamic calculations to establish tentative values of the thermodynamic functions for these molecules.