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JEE Main levelSingle correct optionDifficulty 2 of 3g3023

Which of the following is the correct order of stability?

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

Answer: D

The allyl cation is resonance stabilised. The n-propyl cation is primary with hyperconjugation only, and the vinyl cation has the charge on an

s p

carbon in the plane, with no stabilisation, so it is the least stable.

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