Nonanoic acid (Nonoic acid) is a fatty acid which occurs naturally as esters are the oil of pelargonium. Synthetic esters, such as methyl nonanoate, are used as flavorings. Pelargonic acid is an organic compound composed of a nine-carbon chain terminating in a carboxylic acid. It is an oily liquid with an unpleasant, rancid odor. It is nearly insoluble in water, but well soluble in chloroform and ether.