3-bromo cyclohexane is formed by bromination of cyclohexane with
Answers
Explanation:
The addition of bromine to cyclohexene in carbon tetrachloride solutions has been studied. Results are unreproducible, but when N-bromosuccinimide or N-bromophthalimide is also present to scavenge hydrogen bromide, a slower reaction, second-order in bromine, with reproducible rate constants is observed. This shows a negative overall activation energy. There may be terms in higher powers of [Br2], but the first-order term in bromine is too small to measure. A faster second phase of the reaction begins when all the N-bromo-imide initially present has reacted with the hydrogen bromide formed in side reactions, including those leading to 3-bromocyclohexene and (from adventitious water) to 2-bromocyclohexanol, and is of order 1.5 in bromine
It was investigated whether bromine might be added to cyclohexene in carbon tetrachloride solutions. The results are unreliable, but when N-bromosuccinimide or N-bromophthalimide is present to scavenge hydrogen bromide, a slower reaction, second-order in bromine, is observed with repeatable rate constants. This indicates that the overall activation energy is negative. Higher powers of [Br2] may have terms, but the first-order term in bromine is too tiny to measure. When all of the N-bromo-imide that was previously present has reacted with the hydrogen bromide generated in side reactions, such as those that lead to 3-bromocyclohexene and (from adventitious water) to 2-bromocyclohexene, a faster second phase of the reaction begins.