Homolytic organometallic reactions. Part V. Homolytic bimolecular substitution at boron by the triplet state of ketones
- 1 January 1971
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society B: Physical Organic
- p. 2171-2176
- https://doi.org/10.1039/j29710002171
Abstract
If a mixture of an aliphatic ketone and a trialkylborane is irradiated with u.v. light, the ketone triplet brings about a bimolecular homolytic substitution at the boron centre, and the superimposed e.s.r. spectra of the two radicals which are formed can be observed; the ultimate products of the reaction result from the coupling of these radicals. R1R2CO*+ BR3 3→ R1R2ĊOBR3 2+ R3·→ products By monitoring the intensities of the spectra when two different boranes, or a borane and an olefinic quencher, compete for reaction with acetone triplets, or when substitution and fragmentation reactions of di-isopropyl ketone triplet compete, the above mechanism was established, and kinetic parameters for the substitution reaction were derived. Typically, the reaction between triplet acetone and tri-n-butylborane has a rate constant of 7 × 106 M –1 s–1 at 20°.Keywords
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