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JEE Main levelSingle correct optionDifficulty 2 of 3o1184

Arrange in decreasing rate of reaction with methylamine: (I) benzoyl chloride, (II) benzoic anhydride, (III) methyl benzoate, (IV) N-methylbenzamide.

AI $>$ II $>$ IV $>$ III
BI $>$ II $>$ III $>$ IV
CII $>$ I $>$ III $>$ IV
DI $>$ III $>$ II $>$ IV

Answer: B

Leaving-group ability follows

Cl X^{-} > PhCOO X^{-} > CH X_{3} O X^{-} > CH X_{3} NH X^{-}

(conjugate acid pKa:

- 7

, 4.2, 15.5, about 40). Hence acid chloride

>

anhydride

>

ester

>

amide.

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