Vibrational and conformational analysis of isopropylnitrite

Abstract

The IR and Raman spectra of the vapour and solid phases of isopropylnitrite (CH 3) 2CHONO, and its d 3, d 6 and d 7 isotopically substituted derivatives have been recorded. Additionally, the Raman spectra of the liquid phase of these compounds have been recorded and qualitative polarisation values obtained. For the vibrational analysis the deuterated derivatives d 3, d 6 and d 7 were also prepared. In all the physical states two conformer have been observed. Rigid rotor asymmetric top contour simulation allows the high frequency NO stretch to be assigned to the ( trans,gauche) conformer and the low frequency to the ( cis,gauche) conformer. A temperature study of the Raman spectrum of the liquid phase shows the ( trans,gauche) conformer to be more stable in this phase. In the vapour phase the ( trans,gauche) conformer is also thermodynamically preferred with an enthalpy difference of 2.07 kJ mol −1 (173 cm −1). Solvent studies did not show extreme variations of the peak ratio of the conformational doublets.