tert-Butylbromide reacts with aq. NaOH by SN1 mechanism while n-butylbromide reacts by SN2 mechanism. Why?


Tert-butylbromide undergoes substitution by SN1 mechanism because it is able to form a stable carbocation in the first step after cleavage of the halide group. The carbocation then reacts with the nucleophile OH-. On the other hand, primary halide n-butylbromide cannot form a stable carbocation so it undergoes SN2 mechanism, which is a one-step substitution which involves attack of OH- and simultaneous leaving of X- to form n-butyl alcohol.



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