C4H4N2O2. M.W. 112.09. Uracil is one of the four nucleic acid bases found in RNA. In double-stranded RNA, it pairs with adenine, via two hydrogen bonds in Watson-Crick base pairing. Uracil can be formed by deamination of cytosine. The half-life of uracil in water is 12 years at 100 °C and 3.8 × 108 years at 0 °C at pH 7. It has a UV absorption maximum at 260 nm in neutral solution. It has been found in the Murchison meteorite and has been synthesized in HCN polymerizations and Fischer-Tropsch-type reactions and by the action of electric discharges and irradiations of high-energy protons on simple gas mixtures such as CO–N2–H2O.