Final answer:
The substrate used in Williamson ether synthesis depends on the desired reaction, whether it is SN2, E2, SN1, or E1.
Step-by-step explanation:
In Williamson ether synthesis, the substrate used is an alcohol that contains a leaving group. This leaving group is typically an alkyl halide or a sulfonate ester. The choice of the substrate depends on the desired reaction, whether it is SN2, E2, SN1, or E1.
For SN2: Primary or methyl substrates are preferred.
For E2: Tertiary substrates are preferred.
For SN1 and E1: Tertiary and secondary substrates can both react, while primary substrates usually do not react.