An ab initio Quantum-Chemical Study of C6H5S(O)CH3 and C6H5S(O)CF3

Abstract

The potential functions of internal rotation around the C sp 23S bond in the C 6 H 5 S(O)CH 3 and C 6 H 5 S(O)CF 3 molecules were obtained by ab initio MP2(full)/6-31+G* calculations. The stationary points were identified by solving the vibrational problems. The structures in which the plane of the C sp 23S3C sp 3 bonds is approximately perpendicular to the benzene ring plane correspond to the energy minimum. The barriers to rotation around the C sp 23S bond, corrected for the zero-point vibration energy, are 21.29 [C 6 H 5 S(O)CH 3 ] and 28.98 [C 6 H 5 S(O)CF 3 ] kJ mol !1 . The bond angles (deg) are as follows: 95.7 (CSC), 107.1 (C sp 2SO), 106.3 (C sp 3SO) in C 6 H 5 S(O)CH 3 ; 93.5 (CSC), 108.2 (C sp 2SO), 105.2 (C sp 3SO) in C 6 H 5 S(O)CF 3 . The bond lengths are as follows (A): 1.520 (S=O), 1.804 (C sp 23S), 1.810 (C sp 33S) in C 6 H 5 S(O)CH 3 ; 1.507 (S=O), 1.799 (C sp 23S), 1.870 (C sp 33S) in C 6 H 5 S(O)CF 3 . According to the results of NBO calculations, the formally double S=O bond consists of a strongly polarized covalent s bond (S6O) and an almost ionic bond.An increase in the S=O bond multiplicity relative to a single bond is mainly due to hyperconjugation by the mechanism n(O)6s*(C sp 23S) and n(O)6s*(C sp 33S) and, to a lesser extent, by interaction of the oxygen lone electron pairs with the Rydberg orbitals of the S atoms, characterized by a large contribution of the d component.

Aryl Sulfoxide Radical Cations. Generation, Spectral Properties, and Theoretical Calculations

“…28 In this respect, our results compare well with those of previous calculations. Thus, a rotational barrier of 5.1 kcal/ mol has been recently obtained by MP2/6-31G* calculations, 29 whereas a slightly higher value (8.3 kcal/mol) has been reported by Benassi et al 30 Full optimization of the geometric parameters by MP2/6-31G* calculations 29 showed that the energy minimum conformation of C 6 H 5 SOMe is reached at φ 2 ) 75°and the energy maximum at φ 2 ) 180°. Thus the preferred conformation corresponds to an SO bond nearly eclipsed with the phenyl ring as also suggested by Butenko et al 31 The conformational features of the sulfoxide appear to be slightly sensitive to the bulkiness of the alkyl group.…”

Stereoelectronic Effects in Vinyl Sulfoxides

“…While the stabilizing effect between a CC double bond and a carbonyl group is strongest when the p orbitals are in a collinear arrangement, X-ray crystallographic data and ab initio calculations suggest that this is not valid for SO bonds. In fact, a π bond is almost nonexistent between the S and O atoms, and the bond order is significantly smaller than 2 . Delocalization of the CC double bond into an SO bond is possible when the SO bond is approximately collinear to the π system of the CC double bond, as in the case of sulfoxides 5a − 8a .…”

Enzymatic reactions involving the heteroatoms from organic substrates

“…The main concern with this reaction is to avoid sulfone formation, which is a product from sulfoxide over oxidation. Sulfoxides possess enantiomers due to the sulfur atom as a stereocenter in a pyramidal structure (Alphand and Wohlgemuth 2010, Bzhezovsky et al 2004, Reed and Schleyer 1990, Bzhezovskii et al 2005.…”