The quantitative isomerization of 2, 2-bis (ethylthio)-3, 3-dimethylpent-4-enal to 2, 2-bis (ethylthio)-5-methylhex-4-enal was studied over the temperature range 130-170° C. An investigation of the generality and specific mechanism of this formal [1, 3] sigmatropic shift was conducted with six related compounds. The rearrangements were found to obey first- order kinetics, and on the basis of significant positive entropies of activation (52-106 J deg ...