ULTRAVIOLET IRRADIATION OF PYRIMIDINE DERIVATIVES: III. INFLUENCE OF HYDROGEN CYANIDE ON THE PHOTOLYSIS

The presence of HCN in concentrations up to 0.05 M in aqueous, buffered solutions of uracil, uridine, and 1,3-dimethyluracil has been shown to divert the normal course of the photochemical hydration reactions of these compounds as a result of photochemically induced combination between HCN and the pyrimidine derivative. A simple calculation indicates that HCN is more efficient than water in reacting with activated uracil molecules by a factor of about 103. The possible general significance of such nucleophilic addition reactions in the photochemistry of nucleic acids is discussed.