A collection of molecules tend to do, by and large, what is easiest for them An
alkyl halide with b-hydrogen atoms when reacted with a base or a nucleophile has two
competing routes: substitution (SN1 and SN2) and elimination Which route will be taken
up depends upon the nature of alkyl halide, strength and size of base/nucleophile and
reaction conditions Thus, a bulkier nucleophile will prefer to act as a base and abstracts
a proton rather than approach a tetravalent carbon atom (steric reasons) and vice versa