Given that terminal alkynes react with bromine and water to yield bromoketones. A mechanism for the reaction is to be proposed. To what reaction of alkenes this reaction is analogous is also to be stated. Concept introduction: Addition of bromine to alkynes occurs through the formation of a cyclic bromonium ion intermediate. Water being nucleophilic, if present will attack the bromonium ion to yield an enol. The enol will then tautomerize to a ketone . Thus in thr product a bromine and a hydroxyl group are added to the triple bond. This reaction is similar to the addition of halohydrins to alkenes. To propose: A mechanism for the reaction in which ethynylbenzene reacts with bromine and water to yield a bromoketone is to be proposed. Further to state to what reaction of alkenes this reaction resembles.

Question

Alkynes do not react directly with aqueous acid as do alkenes, but will do so in the presence of mercury(II) sulfate as a Lewis acid catalyst. The reaction occurs with Markovnikov regiochemistry, so the OH group adds to the more highly substituted carbon and the H adds to the less highly substituted carbon. The initial product of the reaction is a vinyl alcohol, also called an enol. The enol immediately rearranges to a more stable ketone via tautomerization. Draw curved arrows to show the movement of electrons in this step of the mechanism. Arrow-pushing Instructions -X티 Hö: H-O -CH3 -CH3 H30*

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Question

Chapter 9.SE, Problem 29AP

Interpretation Introduction

Interpretation:

Given that terminal alkynes react with bromine and water to yield bromoketones. A mechanism for the reaction is to be proposed. To what reaction of alkenes this reaction is analogous is also to be stated.

Concept introduction:

Addition of bromine to alkynes occurs through the formation of a cyclic bromonium ion intermediate. Water being nucleophilic, if present will attack the bromonium ion to yield an enol. The enol will then tautomerize to a ketone. Thus in thr product a bromine and a hydroxyl group are added to the triple bond. This reaction is similar to the addition of halohydrins to alkenes.

To propose:

A mechanism for the reaction in which ethynylbenzene reacts with bromine and water to yield a bromoketone is to be proposed. Further to state to what reaction of alkenes this reaction resembles.

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