The reaiation chemistry of aqueous solutions of [¹⁴C]Benzoic and [¹⁴C}Salicylic Acids

Abstract

Radioactive tracer techniques have been used to study the effect of ionizing radiation (⁶⁰Co γ-radiation and 45 kV X-rays) on [¹⁴C]benzoic acid (both carboxyl- and uniformly-labelled) and on [carboxy-¹⁴C]salicylic acid in aerated aqueous solutions.    The production of o-, m-, and p-hydroxybenzoic acids from benzoic acid (Loebl, Stein, and Weiss 1951) has been cord3rmed. The approximate initial G values for these products were : ortho, 0.74 ; meta, 0.42 ; para, 0.33. The ratio o : m : p was thus approximately 9 : 5 : 4 whereas Loebl, Stein, and Weiss found the corresponding ratio to be 5 : 2 : 10. Benzoic acid and sodium benzoate were also decarboxylated [G(CO₂) : 0.73 ± 0.03]. The extent of decarboxylation was independent of the initial concentration of benzoic acid in the range studied (0.5-7.0 X 10^-3 M). The total reaction of the benzoic acid corresponded to a G value of approximately 2.6. Very little, if any, diphenyl was produced. The main non-volatile products from salicylic acid were 2,3- and 2,5-dihydroxy- benzoic acids which were obtained in the ratio 2,5 : 2,3 :: 1 : 1.6. The 2,4- and 2,6- isomers were not detected. Salicylic acid was also decarboxylated, G(CO₂) being 1 53 ± 0.07 in alkaline solutions. The above results are compared with other results relating to free-radical reactions. The possible use of the decarboxylation of sodium [carboxy-¹⁴C]benzoate as a sensitive dosimeter for ionizing radiation is suggested.