Rearrangements

Wagner-Meerwein rearrangement

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The first-formed cation canot eliminate a proton in an E1 reaction because loss of the only availabel proton would give a very strained alkene. However, migration of a methyl group both stabilizes the cation (it becomes tertiary instead of secondary) and allows E1 elimination of a proton to take place to give a stable alkene. The migration of an alkyl group to a cationic centre is known as a Wagner-Meerwein rearrangement or Wagner-Meerwein shift.

 

 

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