A one-step vapor phase oxidation process produces an unsaturated carboxylic acid, such as acrylic acid or methacrylic acid, from an alkane, such as propane or isobutane, with a mixed metal oxide catalyst and an excess of alkane relative to oxygen. The unreacted alkane and the byproduct alkene are recycled to the reaction zone without separation. Overall yield and productivity of the unsaturated carboxylic improves for such a process. An analogous method for the preparation of unsaturated nitrites is also disclosed.