This work analyzes the structures and energetics of the skewed anticlinal geometries of X–O–O–Y, X–O–S–Y, and X–S–S–Y (where X,Y = H or Me) as well as the corresponding trigonal pyramidal isomers including X–O(O)–Y, X–S(O)–Y, X–O(S)–Y, and X–S(S)–Y (where X,Y = H or Me) with computational approaches. Full geometry optimizations and corresponding harmonic vibrational frequency computations were performed with post-SCF ab initio and density functional methods with a variety of basis sets. The relative energies of these isomers will be discussed. In general, the skewed anticlinal isomers are lower in energy than their trigonal pyramidal counterparts. These energy differences for hydride and methylated isomers containing exclusively oxygen or sulfur span about 5 kcal mol–1. However, molecules with both oxygen and sulfur yield much higher energy differences, some as large as 25 kcal mol–1, across the levels of theory considered. The method and basis set dependence of the relative energies will be discussed. The case of Me–S(O)–Me (dimethyl sulfoxide; DMSO) and the sulfenic ester, Me–S–O–Me, is particularly interesting.

Curious case of DMSO: A computational study

2019 Fall National Meeting

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