MHTCET 15 Apr 2026 Shift 2 Paper

Concept:Acidity of carboxylic acids increases when the conjugate base (carboxylate ion) is more stable.Explanation:The carboxylate ion formed after losing $\mathrm{H}^+$ is stabilised by electron-withdrawing groups.In $\mathrm{ClCH}_2\mathrm{COOH}$, the chlorine atom has a strong $-I$ effect.This pulls electron density away from the $-\mathrm{COOH}$ group.As a result, the negative charge on $\mathrm{ClCH}_2\mathrm{COO}^-$ is delocalised and stabilised.A more stable conjugate base means the acid releases $\mathrm{H}^+$ more easily.The other options contain $-\mathrm{H}$, $-\mathrm{CH}_3$, or $-\mathrm{CH}_2\mathrm{CH}_3$, which are electron-donating groups.Alkyl groups show a $+I$ effect that destabilises the carboxylate ion and weakerens the acid.Therefore, the acidity order is:$$\mathrm{ClCH}_2\mathrm{COOH} > \mathrm{HCOOH} > \mathrm{CH}_3\mathrm{COOH} > \mathrm{CH}_3\mathrm{CH}_2\mathrm{COOH}$$Answer:The strongest carboxylic acid is $\mathrm{ClCH}_2\mathrm{COOH}$.Correct option: D. $\mathrm{ClCH}_2\mathrm{COOH}$