Propose a synthesis for the antihistamine \(p\)-methyldiphenhydramine, given this retrosynthetic analysis. Is \(p\)-methyldiphenhydramine chiral? If so, how many of the possible stereoisomers are formed in this synthesis?

If so, how many stereoisomers are formed in the synthesis process? Answer: To synthesize p-methyldiphenhydramine, we can follow these steps: 1. Start with the reaction of p-chlorobenzyl chloride (1-chloro-4-methylbenzene) with diphenylmethanol (benzhydrol). 2. Perform a Williamson ether synthesis, where the alcohol group on benzhydrol attacks the electrophilic carbon on p-chlorobenzyl chloride. This results in the displacement of the chloride anion and formation of an ether linkage between the benzhydrol and 1-chloro-4-methylbenzene. 3. The product formed in step 2 is p-methyldiphenhydramine. P-methyldiphenhydramine is chiral due to its stereogenic center at the carbon atom connecting the two aromatic rings. There are two possible stereoisomers for this molecule, R and S, as it has only one chiral center.