Pelargonic acid is a C9 straight-chain saturated fatty acid which occurs naturally as esters of the oil of pelargonium. Has antifungal properties, and is also used as a herbicide as well as in the preparation of plasticisers and lacquers. It has a role as an antifeedant, a plant metabolite, a Daphnia magna metabolite and an algal metabolite. It is a straight-chain saturated fatty acid and a medium-chain fatty acid. It is a conjugate acid of a nonanoate. It derives from a hydride of a nonane.