Chapter 10: Q56P (page 540)

Often, compounds can be synthesized by more than one method. Show how this 3° alcohol can be made from the following:
(a) two different ketones
(b) two different alkenes
(c) an ester
(d) a 3° alkyl bromide

Short Answer

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Step by step solution

Starting material

Tertiary alcohol can be easily prepared by the reaction of ketone with Grignard reagent followed by hydrolysis. By acid-catalyzed hydration of alkene gives tertiary alcohol. An ester with two equivalents of Grignard reagent gives tertiary alcohol. It can also be prepared by the reaction of tertiary alkyl bromide with moist Ag₂O. The structure of the product formed is given as:

Formation of the desired product

a) Treatment of 1-cyclopentylbutan-2-one with ethyl magnesium bromide followed by hydrolysis gives the desired product. The reaction is as follows:

Formation of product in reaction a

Treatment of pentan-3-one with (cyclopentyl methyl) magnesium bromide followed by hydrolysis gives the desired product.

Formation of product in reaction a

b) An alcohol can be synthesized by the acid-catalyzed hydration of an alkene. Acid-catalyzed hydration of (2-ethyl but-1-en-1-yl) cyclopentane gives the desired product. The reaction is as follows:

Formation of product in reaction b

Acid-catalyzed hydration of (Z) –(2-ethyl but-2-en-1-yl) cyclopentane gives the desired alcohol. The reaction is as follows:

Formation of product in reaction b

c) The desired tertiary alcohol can be synthesized by the reaction between an ester and two equivalents of Grignard reagent. The reaction is as follows: