Rationalize why the carbonyl oxygen of the ester attacks the aluminum of DIBAL-H instead of the alkoxy oxygen in the following reaction.

• A. The resonance hybrid of the ester shows that the carbonyl oxygen of the ester is more nucleophilic than the alkoxy oxygen.
• B. The resonance hybrid of the ester shows that the alkoxy oxygen of the ester is more nucleophilic than the carbonyl oxygen.
• C. The carbonyl oxygen is sterically less hindered hence it can more easily attack aluminum.
• D. None of these.

Answer: (A)