Quantitative investigation of the ozonisation of quinoline, isoquinoline and some of their homologues

The addition of ozone to quinoline, 2- and 8-methylquinoline, 2,3-, 3,4- and 6,7-dimethylquinoline and isoquinoline has been studied quantitatively. With the quinoline homologues the main initial reaction is an attack of the benzene ring, probably with the formation of a monozonide, which was rapidly converted into a 5,6-, 7,8-diozonide; the diozonide then reacts slowly to form a 3,4-, 5,6-, 7,8-, 9,10-tetraozonide. As a side reaction the pyridine nucleus is attacked initially; however this side reaction leads to the same tetraozonide. Isoquinoline adds on one molecule of ozone in the pyridine nucleus to the extent of about 60 % and two molecules of ozone in the benzene ring to an extent of 40 %. In none of the compounds examined was there any indication of the addition of ozone to a C=N bond. These conclusions, based on a determination of the quantities of ozone taken up, the amount of quinoline reacted and the amount of ammonia formed when the reaction product is hydrolised, are in agreement with the qualitative results of the ozonolysis of quinoline bases already published. 1)