Beta-Phenylethylamine HCl is an ingredient found in certain diet pills. It’s a naturally occurring chemical that is found in the human body but that can also be made synthetically in a lab. What is Beta-Phenylethylamine HCl Beta-Phenylethylamine HCl is called many different things. On a bottle of diet pills, you may see it listed in that way, but it may also be listed as β-phenylethylamine, β-phenethylamine, and phenylethylamine among other names. The International Union of Pure and Applied Chemistry (IUPAC) calls this substance 2-phenylethylamine, which is represented as C8H11N.