Question

What role does the leaving group play on the rate of SN1 versus SN2 reactions? (compare 1-bromo to 1 chloro, 2-bromo to 2-chloro etc).What role does the structure of the substrates play on the rate of SN1 versus SN2 reactions (compare primary,secondary and tertiary that may have the same leaving group)

where is the chiral carbon located?

Answer 1

Bromide ion is a better leaving group than the chloride ion in SN1 reaction, which leads to the formation of carbocation, wherein the formation of carbocation is the rate determining step. However, SN2 reaction is independent of nature of leaving group.

primary,secondary and tertiary that may have the same leaving group , primary substrate facilitate to occur reaction via SN2 reaction, whereas tertiary substrate facilitate to occur the reaction via SN1 reaction (more stable 3⁰ carbocation formation). But in case of secondary substrate has equal probability to proceds via SN1 and SN2 reaction depends on the reactivity of nucleophile and role of solvent.