α-Bromo carbonyl compounds as promoters for the synthesis of (2-bromoethyl)benzene by the anti-Markovnikov addition of hydrogen bromide to styrene

Ronny Neumann, Fernando De La Vega, Adva Bar-On

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

The synthesis of (2-bromoethyl)benzene by the anti-Markovnikov addition of gaseous hydrogen bromide to styrene has been found to be promoted by α-bromo carbonyl compounds such as 2-bromo-2-methylpropanal. These compounds were found to catalyze the "abnormal" addition in a variety of solvents such as ethyl acetate, heptane, toluene and dioxane. High concentrations of 2-bromo-2-methylpropanal and hydrogen bromide and low concentrations of styrene favor formation of (2-bromoethyl)benzene. Using the free-radical catalyzed cyclization of 6-bromo-1-hexene as a probe we have found that the 2-bromo-2-methylpropanal does not in itself initiate a free-radical chain reaction by thermal formation of radicals. Instead, radicals may react with 2-bromo-2-methylpropanal to form relatively stable 2-methylpropanal radicals. The presence of such radicals increases the effective length or inhibits termination of the free-radical chain reaction (propagation) and in the case of hydrobromination of styrene raises the yield of (2-bromoethyl)benzene.

Original languageEnglish
Pages (from-to)1315-1318
Number of pages4
JournalJournal of Organic Chemistry
Volume60
Issue number5
Publication statusPublished - 1995

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Hydrobromic Acid
Carbonyl compounds
Styrene
Free Radicals
Heptanes
Cyclization
Toluene
isobutyraldehyde
(2-bromoethyl)benzene

ASJC Scopus subject areas

  • Organic Chemistry

Cite this

α-Bromo carbonyl compounds as promoters for the synthesis of (2-bromoethyl)benzene by the anti-Markovnikov addition of hydrogen bromide to styrene. / Neumann, Ronny; De La Vega, Fernando; Bar-On, Adva.

In: Journal of Organic Chemistry, Vol. 60, No. 5, 1995, p. 1315-1318.

Research output: Contribution to journalArticle

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AB - The synthesis of (2-bromoethyl)benzene by the anti-Markovnikov addition of gaseous hydrogen bromide to styrene has been found to be promoted by α-bromo carbonyl compounds such as 2-bromo-2-methylpropanal. These compounds were found to catalyze the "abnormal" addition in a variety of solvents such as ethyl acetate, heptane, toluene and dioxane. High concentrations of 2-bromo-2-methylpropanal and hydrogen bromide and low concentrations of styrene favor formation of (2-bromoethyl)benzene. Using the free-radical catalyzed cyclization of 6-bromo-1-hexene as a probe we have found that the 2-bromo-2-methylpropanal does not in itself initiate a free-radical chain reaction by thermal formation of radicals. Instead, radicals may react with 2-bromo-2-methylpropanal to form relatively stable 2-methylpropanal radicals. The presence of such radicals increases the effective length or inhibits termination of the free-radical chain reaction (propagation) and in the case of hydrobromination of styrene raises the yield of (2-bromoethyl)benzene.

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