The oxidation of the fatty dibasic acids and of laevulic acid by hydrogen dioxide in presence of a cupric salt

CONSIDERABLE quantities of the dibasic acids are formed in the laboratory when the higber fatty acids are oxidised by such reagents as alkaline perman- ganate or nitric acid; and oxalic, succinic, adipic and suberic acids have been identified. It is however generally accepted that in vivo the path of the oxidation of the fatty acids does not proceed by way of the dibasic acids. Verkade and Van der Lee [1934] have however recently shown that when decanoic or undecanoic acid was taken by mouth, the terminal methyl group was oxidised and the corre- sponding dibasic acid excreted in the urine. In the laboratory, oxidation of the higher fatty acids with hydrogen dioxide is the process which has been supposed most closely to resemble the normal process of oxidation in the body, and recent experiments [Smedley-MacLean and Pearce, 1934] on the oxidation of palmitic acid, in which this process was catalysed by the addition of a cupric salt, have shown that at 900 there is a rapid breakdown, the end-products being succinic, carbonic and the volatile fatty acids. We therefore investigated the oxidation of the dibasic acids with the same reagents. These acids were found to be more readily attacked than the monobasic acids, so that even at 600 no glutaric or adipic acid and only 10 % suberic acid remained unchanged after 1 hour's heating. When palmitic acid was oxidised by excess of hydrogen dioxide in the presence of copper, there was very little evidence of keto-oxidation: the main products were hydroxy-acids, and there was also evidence of a considerable amount of desaturation. With the dibasic acids, definite evidence was obtained of keto-oxidation: thus laevulic acid was formed from adipic acid, a small quantity of acetonylacetone from suberic acid, and acetone was isolated from the products of oxidation of glutaric acid. With suberic acid however there was definite evidence of hydroxylation, the oc-hydroxy-derivative and a lactonic acid being isolated.