Arrange the following groups in increasing order of their electron withdrawing tendency?
A. –CN
B. –CF3
C. –NO2
D. –Ph
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → D, A, C, B
An electron withdrawing group pulls electron density towards itself. Attached to a carboxyl group, it spreads the negative charge of the carboxylate ion and stabilises it, so the stronger the electron withdrawal, the stronger the acid. So the order of acidity these groups give is also the order of their electron withdrawing tendency.
First, D. –Ph: the weakest; its sp2 carbon pulls electrons only slightly by induction.
Second, A. –CN: a strong withdrawing group (−I and −R).
Third, C. –NO2: stronger than –CN; the positively charged nitrogen pulls hard by −I and −R.
Fourth, B. –CF3: the strongest of the four; three fluorine atoms, the most electronegative element, pull together by the −I effect.
NCERT (2026-27 edition):
Effect of Substituents on the Acidity of Carboxylic Acids
