Force constants of methane. Infrared spectra and thermodynamic functions of isotopic methanes

• Published in: Journal of molecular spectroscopy 1959, Vol.3 (1), p.632-653
• Main Authors: Jones, Llewellyn H, McDowell, Robin S
• Format: Article
• Language: English
• ISSN: 0022-2852; 1096-083X
• DOI: 10.1016/0022-2852(59)90057-8

General quadratic valence force constants have been calculated for the symmetrical methanes ( CY 4) using the most recent experimental data. The F and G matrix elements are given for the isotopic species CY 3 Z and CY 2 Z 2 ( Y and Z are H, D, or T). The fundamental frequencies of CY 3 Z and CY 2 Z 2 were calculated using the CY 4 force constants. Most of the fundamental frequencies of these isotopic methanes were observed. The anharmonic corrections are discussed. From the force constants, zeta values were calculated for the degenerate vibrations of CY 3 Z. The thermodynamic quantities − (F 0 − E 0 0) T , (E 0 − E 0 0) T , S 0, C p 0 , C p 0 , and equilibrium constants for the various H, D, and T isotope exchange equilibria are given at seven temperatures from −180°C to +1000°C.