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Arrange the following benzylic carbocations in order of increasing stability: (I) para-methyl substituted benzyl cation (II) para-nitro substituted benzyl cation (III) benzyl cation bearing two alkyl groups plus a nitro group on the ring

1. I < II < III
2. II < III < I
3. III < II < I
4. III < I < II

Correct answer: II < III < I

Solution

II has a single strongly deactivating -NO2 and is least stable. III has two donating alkyl groups but also one -NO2, giving partial net stabilisation. I has only a donating p-methyl with no withdrawing group, so it is most stable.

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