To produce p-methylaniline from aniline, you can use a methylating reagent such as iodomethane (methyl iodide, CH3I) in the presence of a base, such as potassium carbonate (K2CO3). This reaction is an example of a nucleophilic substitution where the nitrogen atom of aniline acts as a nucleophile and attacks the methyl group of iodomethane, resulting in the formation of p-methylaniline.
It is important to note that the reaction may lead to the formation of both p-methylaniline and o-methylaniline due to the possibility of methyl substitution at both the para and ortho positions relative to the amino group on the benzene ring. However, the use of excess aniline and controlling reaction conditions can favor the production of the para product (p-methylaniline).