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NEET levelSingle correct optionDifficulty 1 of 3g1179

Which of the following carbocations is the most stable?

A $CH X_{3} CH X_{2} CH X_{2} X^{+}$
B $CH X_{3} X^{+}$
C $CH X_{2} = CH - CH X_{2} X^{+}$
D $CH X_{2} = CH X^{+}$

Answer: C

The allyl cation is stabilised by resonance,

CH X_{2} = CH - CH X_{2} X^{+} + CH X_{2} - CH = CH X_{2}

, which spreads the charge over two carbons. The propyl cation has only hyperconjugation, and the vinyl and methyl cations are very unstable.

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