Is the substrate t-butyl bromide best suited for SN1 or SN2 reaction?
If you look at the structure of t- butyl bromide (CH3)3.CBr you will see that the carbon atom attached to the bromine is also attached to THREE methyl groups. These, like all alkyl groups have the effect of pushing electrons towards the carbon atom that is attached to the bromine. This makes it easier to ionise and form the cation (CH3)3C+, (which is stabilised by the flow of electrons towards the positively charged carbon atom). So, in reactions such as hydrolysis where the bromine is eventually replaced by a hydroxide group (OH), the mechanism is likely to contain two steps: 1) a slow ionisation of t-butyl bromide to form the ions (CH3)3C+ and Br- 2) a fast attack by OH- to form t-butyl alcohol (CH3)3COH The slow step is always the one that determines the overall rate of reaction, and you can see that this first step involves only one reactant molecule i.e. (CH3)3CBr So the rate determining step is ‘unimolecular’, and this Nucleophilic Substitution reaction is likely to be of the typ
