Question
Which of the following carbanion expected to be most stable?
A.
$$p{\text{ - }}N{O_2}{C_6}{H_4}\bar C{H_2}$$
B.
$$o{\text{ - }}N{O_2}{C_6}{H_4}\bar C{H_2}$$
C.
$$o{\text{ - }}CHO{C_6}{H_4}\bar C{H_2}$$
D.
$$p{\text{ - }}CHO{C_6}{H_4}\bar C{H_2}$$
Answer :
$$o{\text{ - }}N{O_2}{C_6}{H_4}\bar C{H_2}$$
Solution :
Carbanions are stabilised by electron withdrawing groups. $$ - N{O_2}$$ is stronger electron withdrawing group as compared to $$ - CHO.$$ At $$ortho$$ - position, the effect is more pronounced.