n-Nonanoic acid, commonly known as pelargonic acid, is a mono-carboxylic acid with a linear chain comprising of nine Carbon atoms. Through the odd-numbered Carbon chain: pelargonic acid derivatives often show advantages of lower pour-points and viscosities, coupled with better solubility, in comparison to their even-numbered countertypes.

At the same time: through the absence of double bonds, their stability is very high. In reacting with various polyols: pelargonic acid is the product of choice for high-performance synthetic lubricant esters.