When are rearrangements possible? If a secondary carbocation is vicinal to a tertiary carbon bearing a hydrogen, a 1,2- hydride shift should occur. If a secondary carbocation is vicinal to a quaternary carbon, a 1,2-alkyl shift should occur.

Why do rearrangement reactions occur?

Rearrangements occur to create more stable carbocations. Reviewing carbocation stability from chapter 5 is helpful in identifying carbocations that can undergo rearrangement. Once rearranged, the molecules can also undergo further unimolecular substitution (S _N1) or unimolecular elimination (E1).

Why does rearrangement occur in carbocation?

Whenever an alkyl halide, alcohol or alkene is transformed into a carbocation, the carbocation may be subject to rearrangement. ... Once rearranged, the resultant carbocation will react further to form a final product which has a different alkyl skeleton than the starting material.