Question: what is the structural difference between capsaicin and dihydrocapsaicin?
Answer: Capsaicinoids come from a larger family of chemicals called the vanilloids, compounds that contain the vanillyl group shown right. The only difference between capsaicin and dihydrocapsaicin is the presence of a carbon-carbon double bond. If capsaicin were subject to hydrogenation, dihydrocapsaicin would be formed.