Dear Manu
If the carbon bearing the positive charge is immediately adjacent to a carbon-carbondouble bond, the carbocation is termed an allylic carbocation. The simplest case (all R =H) is called the allyl carbocation.R RRR RGeneric allylic carbocationH2C CH2The allyl carbocationIf the carbon bearing the positive charge is immediately adjacent to a benzene ring, thecarbocation is termed a benzylic carbocation. The simplest case is called the benzylcarbocation.RRGeneric benzylic carbocationHHThe benzyl carbocation
If the carbon bearing the positive charge is part of an alkene, the carbocation is termed avinylic carbocation. The simplest case is called the vinyl carbocation. Note that thecarbon bearing the positive charge has two attachments and thus adopts sp hybridizationand linear geometry.

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