Ozonization of Poly(vinyl alcohol) in Water

Abstract

The rates and products of the ozonization of poly (vinyl alcohol) have been studied at 70°C in neutral and alkaline aqueous solutions. Ozonization of several model compounds and possible intermediates such as 2, 4-pentanediol, 4-methyl-4-hydroxy-2-pentanone and 4-methy1-3-penten2-one was also carried out. Poly (vinyl alcohol) was cleaved quite effectively by ozone to give ketones, carboxylic acids and aldehydes as the major products, the primary reaction being the oxidation of hydroxyl group to a ketone. Formic acid was the major carboxylic acid. It was found that the anomalous ozonolysis played an important role for a double bond conjugated with the carbonyl group. Ozonization in an alkaline aqueous solution was much faster than in a neutral solution and the major products were formic acid and acetic acid, the latter being formed through a β -hydroxy ketone by the reverse aldol type reaction and subsequent oxidation of acetaldehyde. The amount of carboxylic acids formed was larger than that of statistical chain scission of poly (vinyl alcohol). The mechanism of ozonization is discussed.