Williamson Ether Synthesis

Heating an alkyl halide with an alcoholic solution of a sodium alkoxide gives the corresponding ether by an SN2 mechanism: CH3-ONa + Br-C2H5 (heat) gives CH3-O-C2H5 + NaBr (methoxyethane). Because primary alkyl halides are far more susceptible to SN2 attack than secondary or tertiary ones, a MIXED ether bearing one primary and one tertiary alkyl group must be made from the PRIMARY alkyl halide plus the TERTIARY alkoxide (e.g. sodium tert-butoxide + bromomethane gives 2-methoxy-2-methylpropane). The reverse combination fails: tert-butyl bromide + sodium methoxide instead undergoes beta-elimination (E2, since a …