The functional group that shows negative resonance effect is :
- -OH
- -OR
- -COOH
- -NH2
Answer
(3) -COOH
Solution
−R effect: the group pulls π electrons of the conjugated system towards itself (C=O, C≡N, NO2 type groups); a lone pair on the attached atom gives +R.
(A): –OH — lone pair on O donated ⇒ (A) is +R
(B): –OR — lone pair on O donated ⇒ (B) is +R
(C): –COOH — C=O pulls π electrons towards O ⇒ (C) is −R
(D): -NH2 — lone pair on N donated ⇒ (D) is +R
Answer: (3)