The photo-EC? mechanism: reduction of t-butyl bromide by excited-state tetrachlorobenzoquinone radical anion
- 1 January 1990
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Faraday Transactions
- Vol. 86 (17) , 2951-2953
- https://doi.org/10.1039/ft9908602951
Abstract
The mediated reduction of t-butyl bromide by the photochemically excited radical anion of tetrachlorobenzoquinone (TCBQ) is studied in acetonitrile solution using the channel electrode. The reduction of TCBQ in the dark is a reversible one-electron process which forms the corresponding stable radical anion. Upon photoexcitation of the radical anion in the presence of t-butyl bromide, photocurrents are observed and the electrode process is shown to have the characteristics of an EC' mechanism: TCBQ ⇌ TCBQ˙–, TCBQ˙– [graphic omitted] TCBQ˙–*, TCBQ˙–*+ ButBr → TCBQ + ButBr˙–, ButBr˙–→ products. The value of the effective rate constant (rate =keff[TCBQ˙–][ButBr]) for the electron transfer between the radical anion and t-butyl bromide has been evaluated from analysis of the limiting current/flow rate behaviour at the channel electrode. keff was found to be 1315 ± 50 dm3 mol–1 s–1, at a light intensity of 0.120 W cm–2.Keywords
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