Dimethyl sulphone

Table 7 shows the calculated properties of the molecules in this series. The molecular geometries were inferred from available data for H2S and dimethyl sulphone. Methane... 

Dimethyl sulphide, dimethyl sulphoxide, dimethyl sulphone... 

Table 8 gives the complete population analysis for these molecules. Propane has been added for the same reason for which methane was considered above. Figure 14 gives the MOs of dimethyl sulphoxide, and Figure 15 the topmost ones of dimethyl sulphone. 

Goheen and Bennett9 showed that regular nitric acid could be used, in about two molar excess, for the oxidation of dimethyl sulphoxide to dimethyl sulphone in 86% yield. The reaction temperature was 120-150°C with a reaction time of about 4 hours. The mechanism for this reaction was postulated to involve initially a protonated sulphoxide species (which has been shown to be present in other strongly acidic systems101 ) followed by nucleophilic attack by nitrate, and the loss of nitrogen dioxide as shown in equations (4) and (5). 

The use of chlorine as an oxidizing agent for the conversion of sulphoxides into sulphones is completely unsuccessful under anhydrous conditions. In aqueous solutions, the sulphone is formed but this is usually part of a complex mixture of chlorinated sulphoxides, chlorinated sulphones and sulphonyl chlorides89, so that the reaction is usually not very useful as a preparative method for alkyl sulphones. Dimethyl sulphone has however been obtained in 70% yield in one isolated case90. In methanol solution dibenzyl sulphoxide is cleanly oxidized to dibenzyl sulphone and benzyl sulphonyl chloride in reasonable overall yield91. 

The first report of the use of bromine for the oxidation of sulphoxides appeared in 1966116. Diphenyl sulphone was isolated in 0.5-1% yield when the sulphoxide was treated with bromine in aqueous acetic acid for several hours. The yield was increased to about 5% by quenching the reaction with sodium carbonate. A kinetic study117 of a similar reaction involving dimethyl sulphoxide showed no significant yield improvement but postulated that the mechanism proceeds via an equilibrium step forming a bromosulph-onium type intermediate which reacted slowly with water giving dimethyl sulphone as indicated in equation (35). 

The photolysis of dimethyl sulphoxide (at 253.7 nm) in a wide range of solvents has been studied in detail176. Three primary reactions occur, namely (i) fragmentation into methyl radicals and methanesulphinyl radicals, equation (60), (ii) disproportionation into dimethyl sulphone and dimethyl sulphide, equation (61) and (iii) deactivation of the excited state to ground state dimethyl sulphoxide. All chemical processes occur through the singlet state. Further chemical reactions of the initial photochemical products produce species that have been oxidized relative to dimethyl sulphoxide. 

The direct fluorination of sulphones has also been studied210 and this leads to oxidation. At room temperature dimethyl sulphone produced bis(trifluoromethyl)-sulphone and trifluoromethylsulphonyl fluoride in 34% and 15% yields respectively (equation 93). 

Data on other dimethyl sulphones are available from Reference 2. 

TABLE 2. Analytical expressions for some symmetry coordinates" in dimethyl sulphoxide and dimethyl sulphone ... 

As illustrated in Figure 8a, the [18]crown-6 molecule in the 1 2 complex with dimethyl sulfone also adopts an approximate D3d conformation. A methyl group of each dimethyl sulphone guest interacts with alternating oxygen atoms giving CH-O contacts of 2.47, 2.48, and 2.62 A. 

Dimethylsulpholane [1003-78-7] M 148.2, b 128 /77mm, d s 1.1314. Vacuum distd. Dimethyl sulphone [67-71-0] M 94,1, m 109 . Crystd from water. Dried over P2O5. 

Dimethyl sulphone [67-71-0] M 94.1, m 109°. Crystd from water. Dried over P2O5. 

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