Stereochemistry Studies of Some 1,3-dioxane Derivatives by Differential Mass Spectrometry and Computational Chemistry

Abstract

In this work mass spectrometry is for the first time used in the stereo-chemical study of and conformational equilibriums of the saturated 6 atom rings, namely of 1,3 dioxans: cis- and trans-2-phenyl-4-methyl-l,3-dioxane and cis- and trans-2-phenyl-5-methyl-1, 3-dioxane. The technique involved is based on the correlation of the experimental differential mass spectra (diff ms) with the enthalpies of formation obtained through quantum-chemical calculations for the main fragmentation ions from the mass spectra. The lists with the correlation probabilities were obtained using the computer program Chemical Structure Identification by Differential Mass Spectra (CSI Diff ms). The obtained results are in agreement with NMR and X-Ray studies made of these compounds. This also highlighted the preference of the aromatic substituent for the axial position, when the molecule is isolated (in vacuum).