A hydride shift is a rearrangement of atoms in which an unstable carbocation is transformed into a more stable one. Carbocations are ions with positively charged carbon atoms and are often found in organic chemistry.
Hydride shifts are common in reactions involving alcohol and hydrogen halides, including HBr, HCl and HI. Because of its instability and fast reactivity rate, HF is not normally used. Hydride shifts occur when alkenes undergo hydration. Hydride shifts normally occur at low temperatures, but the reaction may be sped up by heating the solution of the cation. Other types of carbocation rearrangements occur, including alkyl and aryl shifts.