ents Hydride shifts give n Summary x.RX HRr包，M 3o72a的m 88 eCgoaYacapi9ghepme,edngo arbocation rearrangements also give new E1 aeegg2ceordesoue 3 3 Summary 9-3 Carbocation Rearrangements Hydride shifts give new SN1 products. Treatment of substituted secondary alcohols produces unexpected results: Rearrangement of an initial secondary carbocation to the more stable tertiary carbocation by a hydride shift results in a rearranged product. Hydride shifts are very fast (faster than SN1 or E1) which is partially due to hyperconjugation in the carbocation weakening the C-H bond): Primary carbocations are too unstable to be formed by rearrangement. Secondary or tertiary carbocations equilibrate readily, leading to a mixture of products when trapped by a nucleophile. Carbocation rearrangement takes place regardless of the precursor leading to the carbocation. Carbocation rearrangements also give new E1 products. Under conditions favoring elimination (elevated temperatures and nonnucleophilic media), carbocations can also rearrange to give rearranged products