On the solubilisation of aromatic amines by purines

Abstract

Abstract The solubilities of the carcinogenic amines, 2‐naphthylamine, 2‐aminofluorene, 2‐anthramine, 4‐aminostilbene, 4‐aminoazobenzene and benzidine in water and in aqueous solutions of caffeine have been examined and it has been found that caffeine exerts a solubilising action on all these amines. Caffeine has quite a marked solubilising action on the simpler amine, 1‐methoxy‐2‐amino‐4‐nitrobenzene and it has been shown that sulphapyridine and sulphathiazole are more soluble in caffeine solutions than in water. The solubility of 2‐aminofluorene has been examined in aqueous solutions of various purines and the results are of the same order as those obtained by Weil‐Malherbe for the solubility of benzpyrene in solutions of the same purines. The most efficient purines are those with the greatest degree of N‐methylation. The influence of a mixture of caffeine and 1,3,7‐trimethyluric acid on the solubility of 2‐aminofluorene in water has been studied and it is shown that the solubilising power of the mixture is less than the sum of the separate effects of each purine on the solubility of the amine. This is taken to mean that the purines antagonise each other probably owing to forces acting between themselves of the same nature as those responsible for the aminofluorene‐purine solubility effects. This effect, which requires further study would probably be of importance in biological systems. Some evidence is given that 2‐phenyl‐quinoline‐4‐carboxylic acid (cinchophen) is solubilised by aqueous solutions of caffeine.