We discuss the reaction of Grignard reagents (organomagnesium compounds) to ketones in Chapter 17. Mechanistically, the reaction proceeds by the nucleophilic addition of a methyl carbanion to the electrophilic carbon of the carbonyl, breaking the C―Oπ bond, resulting in an alkoxide intermediate that is subsequently protonated to produce the 3° alcohol.
(a) Why does this reaction produce a racemic mixture of 3° alcohols?

Predict the products of the following reactions.

(a) allyl bromide + cyclohexyl magnesium bromide

Show how the reaction of an allylic halide with a Grignard reagent might be used to synthesize the following hydrocarbons.

c. 1-cyclopentylpent-2-ene

We discuss the reaction of Grignard reagents (organomagnesium compounds) to ketones in Chapter 17. Mechanistically, the reaction proceeds by the nucleophilic addition of a methyl carbanion to the electrophilic carbon of the carbonyl, breaking the C―Oπ bond, resulting in an alkoxide intermediate that is subsequently protonated to produce the 3° alcohol.

(b) Why, when the substrate is modified slightly, does the reaction result in an excess of one stereoisomer?

In Chapters 8 and 17 we learn two reactions for the synthesis of the alcohol shown. (a) Show a mechanism for each of the reactions. (b) If you were designing a synthetic route, which would be considered more sustainable? Consider all factors. [Assume the starting organic molecules are equally green.]

Starting from bromobenzene and any other reagents and solvents you need, show how you would synthesize the following compounds. Any of these products may be used as starting materials in subsequent parts of this problem.

b. 1-phenylpropene

Which of the following compounds are suitable solvents for Grignard reactions?

(a) n-hexane

(b) CH₃–O–CH₃

(c) CHCl₃

(d) cyclohexane

(e) benzene

(f) CH₃OCH₂CH₂OCH₃

(g)

(h)