Theoretical studies on the structure and electronic properties of aryl sulfides and sulfones

Abstract

Molecular orbital calculations are reported on the structure and electronic properties of diphenyl sulfide using both semiempirical and ab initio methods. Neither the MNDO nor AM1 methods give satisfactory structures, but better results are obtained with the PM3 method. At the ab initio level, the 4-31G basis set with polarization Ž . functions on sulfur alone 4-31GrS* gives comparable results to those obtained with the 6-31G** basis set. The corresponding bond lengths and angles at the sulfur atom of 4-aminophenyl-4Ј-nitrophenyl sulfide and related derivatives of diphenyl sulfone, diphenyl disulfide, and phenylthiosulfonate calculated at the 4-31 GrS* level show a good correlation with crystallographic

A kinetic investigation, supported by theoretical calculations, of steric and ring strain effects on the oxidation of sulfides and sulfoxides by dimethyldioxirane in acetone

“…The correlation line in Fig. 6b [eqn (18)] overestimates log [k 2 /dm 3 mol À1 s À1 ] for (t-Bu) 2 S and (CH 2 ) 2 S by similar amounts. As seen above, the cause is steric for (t-Bu) 2 S but this cannot be the case for (CH 2 ) 2 S which has the least encumbered sulfur centre of all the substrates.…”

“…The added point still does not fall on the line and, as a consequence of the different signs of the coefficient of SE s 0 for the sulfide and sulfoxide subsets discerned above, points for other t-Bu derivatives are displaced from the line and the strict collinearity of the ArSMe and ArSOMe subsets is also lost. Eqn (19) is not therefore an improvement on eqn (18).…”

“…The validity of this method in producing accurate results for these types of S-containing substrate, for the oxidant 1a [and for their derived transition states (see later)] has been well established. [18][19][20][21][22][23][24] The energies calculated were treated in the manner of Dudev and Lim. 25 The ring strain E rs of an x-membered cyclic compound relative to an r-membered cyclic reference compound of the same type is given by eqn ( 9),…”

“…Fig. 6b shows the variation of log [k 2 /dm 3 mol À1 s À1 ] for all of our substrates as a function of calculated values given by eqn (18); the percentage weightings of the standardised variables allow comparison of their relative importance as follows: q S /e, 60.9%; Ss*, 31.2% and DE rs , 7.9%. The definition of the line excludes the points for (t-Bu) 2 S, (CH 2 ) 2 S and (CH 2 ) 3À5 SO.…”

“…The definition of the line excludes the points for (t-Bu) 2 S, (CH 2 ) 2 S and (CH 2 ) 3À5 SO. Eqn (18) is thus a refinement of eqn (15) accommodating the change in ring strain of the included cyclic compounds [the points for (CH 2 ) 6 SO and (CH 2 ) 7 SO coincide]. log [k 2 /dm 3 mol À1 s À1 ] calc = 4.287 À 3.027q S /e À 0.928Ss* À 0.00885DE rs (18) If the data for (t-Bu) 2 S are included in the correlation, SE s 0 becomes significant at a level of probability o0.01, with a positive coefficient [eqn (19)] and the following percentage weightings of the standardised variables: q S /e, 59.0%; Ss*, 25.9%; DE rs , 9.0% and SE s 0 , 6.0%.…”