An investigation by means of correlation analysis into the mechanisms of oxidation of aryl methyl sulfides and sulfoxides by dimethyldioxirane in various solvents.
Relative rate constants have been measured for the oxidation of aryl methyl sulfides and sulfoxides by dimethyldioxirane in acetone, in mixtures of acetone with aprotic co-solvents of both higher and lower relative permittivity, and in aqueous acetone mixtures. Correlation analyses of the effects of substituents in the different solvents show that, with one exception, reactions take place via a single step mechanism in which the formation of the new SO bond and the elimination of acetone occur concertedly. The exception was oxidation of the sulfides in aqueous acetone containing the highest proportion of water of those studied (20% v/v). Here, the behaviour of the reaction is consistent with a two-step mechanism in which the oxidant reversibly attacks the sulfide to form an open-chain sulfonium betaine that subsequently fragments to sulfoxide and acetone. There is no evidence for the participation of an intermediate dioxathietane as has been found in the case of sulfide oxidations by (trifluoromethyl)methyldioxirane in CH(2)Cl(2) and similar aprotic solvents. It is not justified to generalise a mechanism involving a betaine, with or without a derived dioxathietane, to the reactions of dimethyldioxirane in acetone.
Hanson
Peter
P
Department of Chemistry, University of York, Heslington, York YO10 5DD, UK. ph8@york.ac.uk
Hendrickx
Ramon A A J
RA
Smith
John R Lindsay
JR
D000096:Acetone / Q000737:chemistry; D004852:Epoxy Compounds / Q000737:chemistry*; D007700:Kinetics; D010084:Oxidation-Reduction; D012997:Solvents / Q000737:chemistry*; D013223:Statistics as Topic; D013440:Sulfides / Q000737:chemistry*; D013454:Sulfoxides / Q000737:chemistry*; D014867:Water / Q000737:chemistry
D004852:Epoxy Compounds; D012997:Solvents; D013440:Sulfides; D013454:Sulfoxides; D014867:Water; D000096:Acetone; C064455:dimethyldioxirane