A method of producing dicarboxylic acids (e.g., .alpha.,.omega. dicarboxylic acids) by reacting a compound having a terminal COOH (e.g., unsaturated fatty acid such as oleic acid) and containing at least one carbon-carbon double bond with a second generation Grubbs catalyst in the absence of solvent to produce dicarboxylic acids. The method is conducted in an inert atmosphere (e.g., argon, nitrogen). The process also works well with mixed unsaturated fatty acids obtained from soybean, rapeseed, tall, and linseed oils.