INFRARED-SPECTRUM, ABINITIO CALCULATIONS, BARRIERS TO INTERNAL-ROTATION, AND STRUCTURAL PARAMETERS FOR METHYL NITRITE

The fundamental, first, second, and third overtones of the N=O stretching conformationsl doublets of methyl nitrite, CH3ONO, have been observed in the infrared spectrum of the vapor. Rigid-rotor asymmetric top contour simulation of these vibrations allows the high-frequency component to be assigned to the trans conformer and the low-frequency component to the cis conformer. The fundamental, first, and second overtones of the isolated CH stretches of partially deuterated methyl nitrite, CHD2ONO, have been observed in the infrared spectrum of the gas. The CH stretching fundamental of the same compound has been observed in the Raman spectrum of the gas. From these data, the C-H bond distances have been obtained. With use of these C-H distances and the previously reported rotational constants for nine isotopic species of the cis conformer and six of the trans form, a complete r0 structure is reported for both conformers. These structural parameters are compared to the corresponding quantities obtained from ab initio Hartree-Fock gradient calculations employing both the 3-21G and 6-31G * basis sets. Additionally, barriers to internal rotation for the asymmetric, CH3, and CD3 torsions have been calculated from far-infrared data. The pure rotational spectra of CH3ONO and CD3ONO in the far-infrared have been used to determine B + C and DJ values, which are compared to those obtained from microwave. © 1990 American Chemical Society.