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Narrative
Isomers of bromobutane are added to an alkaline aqueous acetone solution containing bromcresol green indicator. The solvolysis is revealed by the indicator changing from green to red as hydrogen bromide is liberated in the reaction. The tertiary halide 2-bromo-2-methylpropane reacts fastest. The secondary halide 2-bromobutane reacts next followed by the more hindered primary halide 1-bromo-2-methylpropane. The primary 1-bromobutane does not react under these conditions. The order of reactivity is characteristic of an S_N1 reaction mechanism.

Discussion
Isomers of C₄H₉Br were added to an alkaline aqueous acetone solution containing bromcresol green indicator. The solvolysis is revealed by the indicator changing from green to red as hydrogen bromide is liberated in the reaction. The tertiary halide 2-bromo-2-methylpropane reacts fastest. The secondary halide 2-bromobutane reacts next followed by the more hindered primary halide 1-bromo-2-methylpropane. The primary 1-bromobutane does not react under these conditions. The order of reactivity of tertiary > secondary > primary halides indicates an S_N1 mechanism in which a free carbocation is formed as described in section 10a.