Butyric acid is prepared industrially by oxidation of butyraldehyde. It is prepared from polyvinyl alcohol by reaction with butyraldehyde. Another way to get the substance is by heating butyraldehyde with hydroxylamine. The butyraldehyde is then hydrogenated to produce butanol. Its complex with rhodium is used in the industrial production of butyraldehyde. The second main aldehyde is butyraldehyde, of which about are prepared by hydroformylation. Butyraldehyde and formaldehyde afford polyvinyl butyral (PVB) and polyvinyl formal (PVF), respectively. Butyraldehyde can be produced by the catalytic dehydrogenation of "n"-butanol. Upon prolonged exposure to air, butyraldehyde oxidizes to form butyric acid.