JEE Main levelSingle correct optionDifficulty 2 of 3g2151
Assertion (A): 2-Methylbenzoic acid is a stronger acid than 4-methylbenzoic acid. Reason (R): An ortho substituent forces the COOH group out of the plane of the benzene ring and so inhibits its resonance with the ring.
ABoth A and R are true but R is not the correct explanation of A
BA is true but R is false
CBoth A and R are true and R is the correct explanation of A
DA is false but R is true
Answer: C
2-Methylbenzoic acid has pKa 3.91 against 4.37 for the 4-isomer. The ortho methyl group twists COOH out of the plane (steric inhibition of resonance), which gives the stronger acid. Hence both statements are true and R explains A.