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JEE Main levelSingle correct optionDifficulty 2 of 3g3029

Which is the correct order of the rate of acid-catalysed hydration of the alkenes $CH X_{2} = CH X_{2}$ , $CH X_{3} CH = CH X_{2}$ and $(CH X_{3}) X_{2} C = CH X_{2}$ ?

A $CH X_{3} CH = CH X_{2} > (CH X_{3}) X_{2} C = CH X_{2} > CH X_{2} = CH X_{2}$
B $CH X_{2} = CH X_{2} > CH X_{3} CH = CH X_{2} > (CH X_{3}) X_{2} C = CH X_{2}$
Call three react at the same rate
D $(CH X_{3}) X_{2} C = CH X_{2} > CH X_{3} CH = CH X_{2} > CH X_{2} = CH X_{2}$

Answer: D

Rate is controlled by protonation to the carbocation. The tertiary

(CH X_{3}) X_{3} C X^{+}

forms most easily, the secondary isopropyl cation next, and the primary ethyl cation the least readily.

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