Bromobutanes, dehydrobromination

Direct experimental evidence for the trans elimination in E2 reactions has been obtained from deuterated -2-bromobutane (the deuterium atom occupies position 3). This compound on dehydrobromination forms trans and cis butene-2 in the ratio of 6 1... 

Problem 6.13 Give the structural formulas for the alkenes formed on dehydrobromination of the following alkyl bromides and underline the principal product in each reaction (a) 1-bromobutane, (b) 2-bromobutane, (c) 3-bromopentane, (d) 2-bromo-2-methylpentane, (e) 3-bromo-2-methylpentane, (/) 3-bromo-2,3-dimethyl-pentane. ... 

Several reaction were examined the dehydrobromination of bromoalkanes, the esterification of benzoic acid with 1-bromobutane and the macrolactonisation of [Pg.138]

Using the models you made in exercise 1 of 1-bromo and 2-bromobutane, demonstrate the result of dehydrobromination. To do so, remove the bromine and a hydrogen from an adjacent carbon insert a double bond between these two carbons. How many isomers are possible from each compound Which is the more stable in the case where two are possible ... 

A remarkable effect of alkali cation exchange of silica gel on the acid-base properties and the selectivity of dehydrobromination of 2-bromobutane has been observed.The reaction proceeds with anti-elimination over Cs- and K-exchanged silica gel in which basic sites play a primary role. On the other hand, the reaction proceeds with syn elimination over silica gel and Na- and Li-exchanged silica gels, all of which are weakly acidic. The observed dependence of the steric courses of the reaction on the acid-base properties was explained by the variation of the reaction mechanism from a concerted elimination over basic surfaces to a carbenium-ion like mechanism over acidic surfaces (Section 4.8). In conformity with this conclusion, the dehydrobromination proceeds with syn elimination over silica gels exchanged with Ba(II), Ca(II), Mg(II) and Ni(II) ions." ... 

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