Major product of the given reaction has to be identified. Concept introduction: H B r addition to alkene under radical condition: Non-markonikov addition of H B r to alkenes occur by a radical mechanism in presence of peroxide, in which a B r · reacts with the π bond of the alkene to create a radical intermediate that H · from H − B r to continue the chain process. The regioselectivity of the products is the opposite of the ordinary Markonikov addition products that form under polar conditions; hence it is useful alternative to polar addition of H − B r in organic synthesis.

Question

(a) (b) (c) Suggest a synthesis of the following alkene (A) using a Wittig reaction strategy. Draw the starting material(s), key reagent and a full reaction mechanism including an explanation of the observed geometry. Which of the following (B) and (C) will favour the enol form? Briefly explain your reasoning. Predict the product(s) and provide a mechanism for each of the following transformations: (i) (ii) OMe OMe Base OEt NaOEt

Answer 1

Question

Chapter 8, Problem 8.32P

(a)

Interpretation Introduction

Interpretation:

Major product of the given reaction has to be identified.

Concept introduction:

HBr addition to alkene under radical condition:

Non-markonikov addition of HBr to alkenes occur by a radical mechanism in presence of peroxide, in which a Br· reacts with the π bond of the alkene to create a radical intermediate that H· from H−Br to continue the chain process. The regioselectivity of the products is the opposite of the ordinary Markonikov addition products that form under polar conditions; hence it is useful alternative to polar addition of H−Br in organic synthesis.

(b)

Interpretation Introduction

Interpretation:

Major product of the given reaction has to be identified.

Concept introduction:

HBr addition to alkene under radical condition:

Non-markonikov addition of HBr to alkenes occur by a radical mechanism in presence of peroxide, in which a Br· reacts with the π bond of the alkene to create a radical intermediate that H· from H−Br to continue the chain process. The regioselectivity of the products is the opposite of the odinary Markonikov addition products that form under polar conditions; hence it is useful alternative to polar addition of H−Br in organic synthesis.

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