Solvolysis of tertiary and secondary haloalkanes

We have learned that the rate of the Sn2 reaction diminishes drastically when the reacting center changes from primary to secondary to tertiary. These observations, however, pertain only to bimolecular substitution. Secondary and tertiary halides do undergo substitution, but by another mechanism. In fact, these substrates transform readily, even in the presence of weak nucleophiles, to give substitution products. 

For example, when 2-bromo-2-methylpropane (tert-butyl bromide) is mixed with water, it is rapidly converted into 2-methyl-2-propanol (tert-butyl alcohol) and hydrogen bromide. Water is the nucleophile here, even though it is poor in this capacity. Such a transformation, in which a substrate undergoes substitution by solvent molecules, is called solvolysis, such as methano-lysis, ethanolysis, and so on. When the solvent is water, the term hydrolysis is applied. 

Nucleophile red Electrophile blue Leaving group green 

2-Bromopropane is hydrolyzed similarly, albeit much more slowly, whereas 1-bromopropane, bromoethane, and bromomethane are unchanged under these conditions. 

Solvolysis also takes place in alcohol solvents. 

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