| Abstract
| - Gas-phase activation data were obtained for model sulfoxide elimination reactions. The activationenthalpy for methyl 3-phenylpropyl sulfoxide is 32.9 ± 0.9 kcal/mol. Elimination by methyl vinylsulfoxide to form acetylene has an enthalpic barrier of 41.6 ± 0.8 kcal/mol and that of 3-phenylpropylmethanesulfinate to form hydrocinnamaldehyde is 34.6 ± 0.6 kcal/mol. Calculations at the MP2/6-311+G(3df,2p)//MP2/6-31G(d,p) level for simplified models of these reactions provide barriers of32.3, 40.3, and 32.7 kcal/mol, respectively. A series of other compounds are examined computationally, and it is shown that the substituent effects on the sulfoxide elimination reaction are muchmore straightforward to interpret if ΔH data are available in addition to the usually determinedΔH⧧. The activation enthalpy of the reverse addition reaction is also subject to structural variationand can usually be rationalized on the basis of nucleophilicity of the sulfur or polarity matchingbetween the sulfenic acid and olefin derivative.
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