Capsaicin (C₁₈H₂₇NO₃) — Properties, Uses & Safety

Overview

Capsaicin (C18H27NO3) is the organic compound responsible for the burning sensation experienced when eating chili peppers. With a molar mass of 305.41 g/mol, capsaicin is a white crystalline solid in its pure form, though it is intensely pungent even in minute quantities. It belongs to a family of compounds called capsaicinoids, found naturally in plants of the genus Capsicum. The heat of chili peppers is measured on the Scoville scale, with pure capsaicin rating approximately 16 million Scoville Heat Units (SHU). Capsaicin works by binding to the TRPV1 (transient receptor potential vanilloid 1) receptor on sensory neurons — the same receptor that detects actual heat and physical abrasion. This is why eating spicy food literally feels like burning, even though no tissue damage occurs. The IUPAC name of capsaicin, (E)-N-(4-hydroxy-3-methoxybenzyl)-8-methylnon-6-enamide, reveals its complex structure featuring a vanilloid ring, an amide bond, and a long hydrocarbon tail. GHS hazard codes include H302 (harmful if swallowed), H312 (harmful in contact with skin), H315 (causes skin irritation), H317 (may cause allergic skin reaction), H319 (causes serious eye irritation), and H335 (may cause respiratory irritation). Beyond culinary use, capsaicin is found in topical pain-relief creams where it depletes substance P from nerve endings, providing relief for arthritis and neuropathic pain. It is also the active ingredient in pepper spray used for self-defense. For chemistry students, capsaicin is an engaging molecule that connects organic chemistry functional groups — including amides, ethers, phenols, and alkenes — to biological receptor interactions. It illustrates how molecular shape determines biological activity, a key concept in medicinal chemistry and pharmacology.

IUPAC Name

(E)-N-(4-hydroxy-3-methoxybenzyl)-8-methylnon-6-enamide

CAS Number

404-86-4

PubChem CID

1548943

Molecular Formula

C₁₈H₂₇NO₃

Molar Mass

305.412 g/mol

State at STP

solid

Appearance

White crystalline solid; intensely pungent