Which of the following halides undergoes E1 elimination fastest when heated in ethanol without any added strong base?

A2-bromo-2-methylpropane
B1-bromobutane
C2-bromobutane
Dbromoethane

Answer: A

E1 rate follows carbocation stability. The tertiary halide gives the tert-butyl cation, which is far more stable than secondary or primary cations, so it reacts fastest.

Practice Organic Reaction Mechanisms IV: Elimination More on E1 mechanism and carbocation rearrangement

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