Cubbage J W, Guo Y, McCulla R D, Jenks W S
Department of Chemistry, Iowa State University, Ames, IA 50011-3111, USA.
J Org Chem. 2001 Dec 28;66(26):8722-36. doi: 10.1021/jo0160625.
Gas-phase activation data were obtained for model sulfoxide elimination reactions. The activation enthalpy for methyl 3-phenylpropyl sulfoxide is 32.9 +/- 0.9 kcal/mol. Elimination by methyl vinyl sulfoxide to form acetylene has an enthalpic barrier of 41.6 +/- 0.8 kcal/mol and that of 3-phenylpropyl methanesulfinate 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 of 32.3, 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 much more straightforward to interpret if DeltaH data are available in addition to the usually determined DeltaH++. The activation enthalpy of the reverse addition reaction is also subject to structural variation and can usually be rationalized on the basis of nucleophilicity of the sulfur or polarity matching between the sulfenic acid and olefin derivative.
获得了模型亚砜消除反应的气相活化数据。3-苯基丙基亚砜甲酯的活化焓为32.9±0.9千卡/摩尔。甲基乙烯基亚砜消除生成乙炔的焓垒为41.6±0.8千卡/摩尔，3-苯基丙基甲亚磺酸盐生成氢化肉桂醛的焓垒为34.6±0.6千卡/摩尔。在MP2/6-311+G(3df,2p)//MP2/6-31G(d,p)水平上对这些反应的简化模型进行计算，得到的势垒分别为32.3、40.3和32.7千卡/摩尔。通过计算研究了一系列其他化合物，结果表明，如果除了通常测定的ΔH++之外还能获得ΔH数据，那么取代基对亚砜消除反应的影响就更容易解释。逆加成反应的活化焓也会受到结构变化的影响，通常可以根据硫的亲核性或亚磺酸与烯烃衍生物之间的极性匹配来进行合理说明。
