Wagner-Meerwein rearrangement

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NOTE: Important charges and non-bonding electrons are shown throughout the animation except during the transition phase

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.

R. R. Naredla and D. A. Klumpp, Chem. Rev., 2013, 113, 6905–6948.