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Density functional investigation of reaction of borohydride cation BH2+ with propylene

Zheng-Wang Qu1, Hui Zhu, Ze-Sheng Li

  • 1State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Center of Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, PR China. qzwzhh@hotmail.com

Journal of Computational Chemistry
|December 4, 2003
PubMed

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In addition to the oxymercuration–demercuration method, which converts the alkenes to alcohols with Markovnikov orientation, a complementary hydroboration-oxidation method yields the anti-Markovnikov product. The hydroboration reaction, discovered in 1959 by H.C. Brown, involves the addition of a B–H bond of borane to an alkene giving an organoborane intermediate. The oxidation of this intermediate with basic hydrogen peroxide forms an alcohol.
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In the presence of organic peroxides, the addition of hydrogen bromide to an alkene yields the isomer that is not predicted by Markovnikov’s rule. For example, the addition of hydrogen bromide to 2-methylpropene in the presence of peroxides gives 1-bromo-2-methylpropane. This addition reaction proceeds via a free radical mechanism, which reverses the regioselectivity. The free radical reaction mechanism involves three stages: initiation, propagation, and termination.