Choose the member of each pair that will react faster by the SN1 mechanism.
(a) 1-bromopropane or 2-bromopropane
(b) 2-bromo-2-methylbutane or 2-bromo-3-methylbutane
(c) n-propyl bromide or allyl bromide
(d) 1-bromo-2,2-dimethylpropane or 2-bromopropane
(e) 2-iodo-2-methylbutane or tert-butyl chloride
(f) 2-bromo-2-methylbutane or ethyl iodide
Answer :
The structure that can form the more stable carbocation will undergo SN1 mechanism faster
(a) 1-bromopropane or 2-bromopropane
2-Bromopropane will react faster by the SN1 mechanism than 1-bromopropane because secondary alkyl halide while 1-Bromopropane is primary alkyl halide .In general ,secondary alkyl halides are more favourable for SN1 reaction than primary alkyl halides .
(b) 2-bromo-2-methylbutane or 2-bromo-3-methylbutane
2-Bromo-2-methylbutane will form a tertiary carbocation will undergo SN1 mechanism because it is the most stable carbocation and 2-bromo-3-methylbutane forms secondary carbocation which is less stable than tertiary carbocation.
(c) n-propyl bromide or allyl bromide
n-propyl bromide is not having any resonance structure so the formation of stable carbocation is difficult in this case .whereas allyl bromide is having double bond and probably having resonance structures and forming the stable carbocation and thus it can form SN1 mechanism faster than the n-propyl bromide .
(d) 1-bromo-2,2-dimethylpropane or 2-bromopropane
