Question

Which of the following group show +M > –I effect?

• A. -F
• B.
• C.
• D. –COOH

Answer 1

The correct option is B

The oxygen of the ester group is in conjugation with the carbonyl of the $-COR$ group. The carbonyl group is electron withdrawing and this rules out the aldehyde and carboxylic acid groups as unsuitable as per the question.

The oxygen of the $-O-CO-R$ is relatively free to conjugate its one of the two lone pairs. This is despite the fact that the $O-CO$ bond has double bond character.