The Raman (4000-10 cm-') and infrared (4000-80 cm-') spectra of methyl nitrite, CH,ONO, and methyl nitrite-d, were recorded in the gas and solid phases. Additionally, the Raman spectra of the pure liquids were recorded and qualitative depolarization values were obtained. Support for the interpretation of these new data is provided by ab initio calculations using the 6-31G* basis set. Complete equilibrium geometries have been determined for both conformers, as well as structures for every 30" rotation about the N-O bond. These calculations give a cis/truns barrier of 4015 cm-' (11.5 kcal mol-I), a trans/& barrier of 3504 cm-' (10.0 kcal mol-') and an enthalpy difference between conformers of 511 cm-' (1.5 kcal mol-') with the cis form being more stable. From a variable temperature Raman study of liquid methyl nitrite-d, it is concluded that the cis form is also more stable in this phase with an enthalpy difference between conformers of 262 2 3 cm-' (750 f 9 cal mol-I). A complete assignment of the vibrational fundamentals is proposed based on band contours, depolarization values, group frequencies and shift factors for the two isotopomers. These assignments are supported by normal coordinate analyses using the ab initio force fields to obtain frequencies and potential energy distributions for both conformers. ~

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Raman spectra (4000-10 cm-') of gas, liquid and solid ethyl nitrate were recorded. The qualitative depolarization values were obtained from the spectrum of the liquid. A vibrational assignment for the normal modes is proposed based on depolarization values, group frequencies and normal coordinate calculations. The structures for the trans and gauche conformers have been determined from ab initio HartreeFock gradient calculations using the Gaussian42 program with both the 3-216 and 6-31G* basis sets. From this calculation at the 631G* level, the energy difference between the more stable trans conformer and the higher energy gauche conformers was found to be 474 cm-' (1.36 kcal mol-') with a gauche dihedral angle (CCON) of 79' . The trans to gauche and gauche to gauche barriers are 990 cm-' (2.83 kcal mol-') and 3152 cm-' (9.01 kcal mol-'), respectively. Barriers to internal rotation for the CH, and NO, groups were also obtained from ab initio calculations. For the trans conformer the values are 1304 em-' (3.73 kcal mol-') and 2702 cm-' (7.73 kcal mol-') and for the gauche conformer they are 1161 cm-' (3.32 kcal mol-') and 2758 (7.89 kcal mol-') for the CH, and NO, barriers, respectively. Normal coordinate calculations were also performed for both conformers utilizing force fields calculated from the 3-21G basis set which support the vibrational assignments. The results of this investigation are compared with similar data on some corresponding molecules.