Sulfonation reactions of alkyl benzenes
The sulfonation of some alkylbenzene homologues and isomers with sulfur trioxide gas has been studied in order to determine any differences in their reactivity. Relative rate kinetics has been used to demonstrate subtle differences in reactivity towards substitution on the benzene ring. A decrease i...
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Swansea University
2000
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| Online Access: | http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636444 |
| Summary: | The sulfonation of some alkylbenzene homologues and isomers with sulfur trioxide gas has been studied in order to determine any differences in their reactivity. Relative rate kinetics has been used to demonstrate subtle differences in reactivity towards substitution on the benzene ring. A decrease in the relative rate is shown to be consistent with an increasing steric parameter in the alkyl chain. The results are discussed in terms of alkyl chain length and the degree of branching in the alkyl chain. Cleavage of a range of di-<I>p</I>-substituted diaryl sulfones has been shown to occur in concentrated sulfuric acid at elevated temperatures. The kinetics of these reactions was determined from second order rate plots, and the activation energies for the reactions were calculated from Arrhenius plots of the rate data over a range of temperatures. Two reaction mechanisms are postulated in which the initial step is protonation at the <I>ipso</I> position of one benzene ring. Plots of reaction rates <I>versus</I> σ<SUB>p</SUB><SUP>+</SUP> values for the various functional groups provide support for initial protonation at the most electron rich aromatic ring. The first oxidation of a range of symmetrical <I>para</I>-substituted diaryl sulfides is reported using potassium hydrogen persulfate (Oxone) in acetone/water under reflux without the use of a buffer. Preparative scale reactions were straightforward and afforded high isolated yields of the sulfone, with no sulfoxide. |
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