REARRANGEMENT STUDIES WITH C14: VII. THE ACETOLYSIS OF METHYL-C14-ISOPROPYLCARBINYL p-TOLUENESULPHONATE

Acetolysis of methyl-C14-isopropylcarbinyl p-toluenesulphonate (I) at reflux temperature gave a mixture of 2-methyl-2-butene (II), 2-methyl-1-butene (III), and 3-methyl-1-butene (IV) with no isolatable quantity of substitution product. The relative amounts of olefins II, III, and IV were measured by gas–liquid chromatography to be 80%, 18%, and 2%, respectively, and these were substantially verified by estimations with the isotope dilution technique. When the acetolysis was carried out at 50 °C, besides olefins II, III, and IV, present in relative amounts of 83%, 16%, and 1%, respectively, as determined by gas–liquid chromatography, a small quantity of substitution product, t-amyl acetate (V), was obtained. Under the conditions of acetolysis at reflux temperature, however, V was found to decompose to olefins II and III. Degradation of the olefinic products of acetolysis gave, among other compounds, radioactive acetone. Since acetone was derived from the chief product, II, its activity could be attributed to an isotope position rearrangement resulting from a 1,2-methide shift as one of the processes that gave rise to olefin II. This rearrangement amounted to about 2.5% and 0.9%, respectively, in olefin II from acetolysis at reflux temperature and at 50 °C. Considering all these results, it may be concluded that both substitution and elimination reactions could take place during acetolysis of I. The substitution reaction proceeded with neighboring hydrogen participation to yield t-amyl acetate, which would decompose to olefins II and III at reflux temperature under the acetolysis conditions. In the E1 reaction during acetolysis of I, processes involving no neighboring group participation to give olefins II and IV, with neighboring hydrogen participation to give olefins II and III, and with neighboring methyl participation to give isotopically rearranged olefins II and IV, all occurred, the process with neighboring hydrogen participation being predominant.