To determine which reactant will give the shown alcohol upon reaction with one mole of phenyl magnesium bromide (PhMgBr) followed by acidic hydrolysis, we must identify the mechanism of Grignard reactions with nitriles and ketones.
Grignard reagents such as PhMgBr are known to add to carbonyl compounds like ketones, aldehydes, and also nitriles. The initial step involves the nucleophilic addition of the Grignard reagent to the carbon of the carbonyl or cyano group.
In the presence of a nitrile like R-C≡N, the Grignard reagent forms an intermediate imine which, upon hydrolysis, yields the corresponding ketone. This ketone can further undergo addition with another molecule of PhMgBr to ultimately give a tertiary alcohol.
The target molecule shown is a tertiary alcohol where the carbon is bonded to a phenyl group, a methyl group, and another phenyl group (Ph_2CH(OH)).
Let's evaluate the options:
CH_3-C≡N: Reaction with PhMgBr would lead to a ketone with one methyl and one phenyl group after hydrolysis, producing CH_3-CO-Ph, which does not match the target compound after further reaction.
Ph-C≡N: This would form a ketone Ph-CO-Ph that cannot form the alcohol in question.
: This compound is acetophenone (Ph-CO-CH_3), which can react with PhMgBr to form the desired tertiary alcohol.
The last option (with an image) corresponds to acetophenone, which will give the target tertiary alcohol after treatment with PhMgBr and hydrolysis.
Thus, the correct answer is the reactant with the structure of acetophenone:
