Hydrolysis of Y-CH2CH2-Cl in water is fastest for which Y?

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NEET levelSingle correct optionDifficulty 1 of 3o3120

Hydrolysis of $Y - CH X_{2} CH X_{2} - Cl$ in water is fastest for which Y?

A $H X^{-}$
B $F X^{-}$
C $CH X_{3} CH X_{2} X^{-}$
D $CH X_{3} S X^{-}$

Answer: D

Sulfur has easily available lone pairs and is a good internal nucleophile; it displaces chloride to give a cyclic episulfonium ion (anchimeric assistance). Ethyl and hydrogen have no lone pair, and fluorine is too electronegative and too tightly holds its pairs to participate.

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Hydrolysis of $Y - CH X_{2} CH X_{2} - Cl$ in water is fastest for which Y?