A C7, straight-chain fatty acid that contributes to the odour of some rancid oils. Used in the preparation of esters for the fragrance industry, and as an additive in cigarettes. ChEBI: Heptanoic acid is a C7, straight-chain fatty acid that contributes to the odour of some rancid oils. Used in the preparation of esters for the fragrance industry, and as an additive in cigarettes. It has a role as a plant metabolite. It is a medium-chain fatty acid and a straight-chain saturated fatty acid. It is a conjugate acid of a heptanoate.