The emprical general harmonic force field of ethane

Abstract A total of 175 spectroscopic data, accumulated from 10 isotopic species of ethane, are used to define all 22 parameters of the harmonic potential function within narrow limits. Before calculation, numerous Fermi resonances have been identified and quantified through infrared and Raman spectroscopic studies of CH3CD3 and its 13C isotopic species. This is an essential prerequisite to such an investigation, without which a self-consistent empirical data set cannot be achieved from which to determine physically meaningful force constants. Comparison of the empirical force constants with those predicted by scaled ab initio calculations shows an excellent degree of correspondence in all force constants, and confirms that both approaches can lead to essentially identical results. Calculated values of spectroscopic data of reliable quality are listed. These should be of value to future spectroscopic investigation of isotopic ethanes and for resolving the many resonance perturbations which are present.

[1]  F. Abraham,et al.  A generalized diffusion equation for nonuniform fluid systems, with application to spinodal decomposition , 1976 .

[2]  J. P. Peña,et al.  Methyl cianide: Spectroscopic studies of isotopically substituted species, and the harmonic potential function , 1978 .

[3]  G. E. Hansen,et al.  The Potential Constants of Ethane , 1952 .

[4]  Warren J. Hehre,et al.  Representations of molecular force fields. I. Ethane: Ab initio and model, harmonic and anharmonic , 1975 .

[5]  T. Shimanouchi,et al.  Rotation-vibration spectra and rotational, Coriolis coupling and potential constants of ethane, ethane-d6 and ethane-1, 1, 1-d3 , 1971 .

[6]  P. Pulay,et al.  Comparison of the ab initio force constants of ethane, ethylene and acetylene , 1974 .

[7]  Force field, dipole moment derivatives, and vibronic constants of benzene from a combination of experimental and ab initio quantum chemical information , 1981 .

[8]  M. Fujio,et al.  Microwave spectra of 13CH3 12CD3 and 12CH3 13CD3 and the C–C bond length of ethane , 1977 .

[9]  E. Hirota,et al.  Microwave Spectrum of Ethane , 1971 .

[10]  H. Heise,et al.  Rotational fine structure of the perpendicular band, ν7, of ethane-1,1,1-d3 , 1980 .

[11]  L. R. Posey,et al.  The Infra‐Red Absorption Spectrum of Mono‐Deutero‐Ethane under High Resolution , 1949 .

[12]  C. Altona,et al.  Application of self-consistent-fieldab initiocalculations to organic molecules: II. Scale factor method for the calculation of vibrational frequencies fromab initioforce constants: ethane, propane and cyclopropane , 1976 .

[13]  S. Saito,et al.  Barrier to internal rotation in ethane from the microwave spectrum of CH3CHD2 , 1979 .

[14]  J. Duncan.  The calculation of force constants and normal coordinates—V constrained force fields for a series of methyl and dimethyl compounds of 3-fold symmetry , 1964 .

[15]  H. L. Welsh,et al.  THE RAMAN SPECTRUM OF ETHANE-d$sub 6$ , 1962 .

[16]  D. E. Shaw,et al.  THE RAMAN SPECTRUM OF ETHANE-1,1,1-d3 , 1967 .

[17]  J. Susskind.  Theory of torsion-vibration-rotation interaction in ethane and analysis of the band ν11 + ν4☆ , 1974 .

[18]  A. J. Bruce,et al.  Infrared spectroscopic studies of partially deuterated ethanes and the r0, rz, and re structures , 1979 .

[19]  Yasuki Endo,et al.  Microwave spectra of deuterated ethanes: Internal rotation potential function and rz structure , 1981 .

[20]  H. Heise,et al.  Infrared rotation-vibration spectra of ethane: The perpendicular band, ν7, of C2H6 , 1980 .

[21]  J. Hougen.  Perturbations in the vibration-rotation-torsion energy levels of an ethane molecule exhibiting internal rotation splittings , 1980 .

[22]  J. Susskind.  Torsion-vibration-rotation interaction in ethane: The bands ν12 + ν4, ν8 and ν6☆ , 1974 .

[23]  N. Sheppard,et al.  Anharmonicity of CH3 deformation vibrations and Fermi resonance between the symmetrical CH3 stretching mode and overtones of CH3 deformation vibrations , 1972 .