Nitrous oxide is known to provide non-catalytic liquid phase oxidation of alkenes to carbonyl compounds (the carboxidation reaction). This paper shows that carboxidation of cyclohexene can be successfully conducted in the gas phase, too. The gas phase carboxidation is a second order reaction proceeding at 325-450 degrees C under 3-16 bar pressure with an activation energy of 26 kcal/mol. The reaction mechanism does not involve free radical steps and leads to cyclohexanone as a main product.