For the reaction shown, which of the compounds below would be the expected major, and final, organic product?

Question

Quizplus · Accepted Answer

The reaction shown is a Grignard reaction, where the Grignard reagent (an organomagnesium halide) attacks the carbonyl carbon of the aldehyde. The resulting intermediate is an alkoxide ion, which can be protonated by water to yield the final alcohol product. Since the Grignard reagent in this case is phenylmagnesium bromide (C6H5MgBr), the nucleophile is a phenyl group (-C6H5). 
Out of the given compounds, only compound II has a carbonyl carbon that can be attacked by a phenyl group. The resulting intermediate would be a tertiary alcohol since the phenyl group adds to the carbonyl carbon, which is one of two carbons already bearing alkyl substituents. When the alkoxide ion intermediate is protonated, the final product would be compound II with an additional alcohol functional group (-OH) on the carbon that was previously the carbonyl carbon.

For the Reaction Shown, Which of the Compounds Below Would