(f)Steric crowding increases more when hydroxide adds to the axial carbonyl group.20.32Compound A is thep-toluenesulfonate ester (tosylate) oftrans-4-tert-butylcyclohexanol. Theoxygen atom of the alcohol attacks the sulfur ofp-toluenesulfonyl chloride, and so the reactionproceeds with retention of configuration.The second step is a nucleophilic substitution in which benzoate ion displaces p-toluenesulfonatewith inversion of configuration.Saponification of cis-4-tert-butylcyclohexyl benzoate in step 3 proceeds with acyl–oxygen cleav-age to give cis-4-tert-butylcyclohexanol.20.33Reaction of ethyl trifluoroacetate with ammonia yields the corresponding amide, compoundA. Com-pound A undergoes dehydration on heating with P4O10to give trifluoroacetonitrile, compound B.Grignard reagents react with nitriles to form ketones.tert-Butyl trifluoromethyl ketone is formedfrom trifluoroacetonitrile by treatment withtert-butylmagnesium chloride followed by aqueoushydrolysis.
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