When a reaction gives both an SN1 product and an E1 product how to I distinguish which on is the major one? Similarly, how do I distinguish between SN2 and E2?
The& SN2& and& E2& reactions share a great number of similarities. Both require a good leaving group.& SN2& reactions require a good nucleophile, while& E2 reactions require a good base. In most cases, however, a good nucleophile is also a good base.
Thus& S N 2& and& E2& often compete in the same reaction conditions. The winner is determined by the degree of& α and& β branching and the strength of the nucleophile/base. Increased& α and& β branching and strong basicity favor& E2& elimination. Increased nucleophilicity favors the& SN2 reaction.