Yield of free-ions in the radiolysis of formamide, a liquid of very high dielectric constant

Solutions of N2O in liquid formamide (dielectric constant 109) gave a yield of N2 during γ-radiolysis of G(N2) = 3.3 ± 0.3. Competition between N2O and other scavengers, including water, ethanol, acids, AgNO3, and CdI2 strongly resembled the pattern of reactivity characteristic of solvated electrons found in other polar liquids. Furthermore, the yield obtained (3.3) was consistent with the high dielectric constant and predicted for the free-ion yield by Freeman's model assuming a total ionization of 4.7. However, the absence of an absorption band in nanosecond pulse radiolysis experiments suggests that solvated electrons were not present 10−9 s after the passage of the ionizing radiation. It is quite possible that in this system "solvent anions" (or other reactive reducing ions) were formed in yield equal to the "free-ion" yield. This presupposes that formamide anions readily reduce N2O and Ag+, are inactivated by H+ and do not react with water and alcohols.The high dielectric constant apparently leads to large yields of comparatively long-lived (> 10−7 s) reducing ions (free-ion yield of 3.3) accompanied by rather small yields of H atoms and simple molecular decomposition products. In these respects the radiolysis decomposition of formamide resembles that of water.