The electrochemical reduction of benzoate esters in aprotic media leads to relatively stable radical anions. The radical anions decompose to electroinactive products in an initial EC mechanism. At long‐time scales and/or higher concentrations, the benzoate esters begin to exhibit more complicated mechanistic behavior. The initial rates of decomposition of several benzoate ester radical anions have been determined by digital simulations of cyclic voltammograms, double potential step experiments, and rotating ring‐disk techniques. On short‐time scales, the reduction of t‐butyl p‐toluate is a good example of pure EC mechanistic behavior. The final decomposition products are many and complex for most of the esters studied, but t‐butyl benzoate cleanly gives benzoate anion and t‐butyl p‐t‐butyl benzoate.
620 0 0 10 cis and trans cis and t r a n s
11From these observations we conclude that the rearrangements of a-methylene ketones generalized in eq 3 and 4 involve singlet biradical intermediates. l 1 For the y-hydrogen abstraction leading to cyclobutyl ketones these intermediates must have a lifetime sufficient to permit the rotatim about the cr,p carbon-carbon bond required for ring closure. It is noteworthy in this regard that evidence is on record favoring short-lived biradical intermediates in the singlet y-hydrogen abstraction reactions of saturated alkanones12 and also implicating longer-lived singlet biradicals as intermediates in the related abstraction processes of P , y unsaturated ketones. l 3 , I 4 (1 1) A theoretical discussion detailing the oversimplifications inherent in use of simple structures for such species is given by L. Salem and C. Rowland, Angew. Chem., 84, 86 (1972); Angew. Chem., Int. Ed. Engf., 11,92 (1972). (12) L. M. Stephenson, P. R. Cavigli, and J. L. Parlett, J . Amer. Chem. Soc., 93, 1984 (1971); C. P. Casey and R . A. Boggs, ibid., 94, 6457 (1972). (13) J. C. Dalton and H.-F. Chan, J. Amer. Chem. Soc., 95, 4085 (1973). See also P. S. Engel and M. A. Schexnayder, ibid., 94, 9252 (1972).
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