Radical production in the radiolysis of liquid pyridine

A combined experimental and theoretical approach has been used to probe the radiolytic decomposition of liquid pyridine. The major single condensed phase product in the gamma-radiolysis of pyridine is dipyridyl with a yield of 1.25 molecules/100 eV total energy absorbed. Scavenging studies suggest that most, if not all, dipyridyl has a radical precursor, but only about 10% of that is due to the pyridyl radical. The remainder of the dipyridyl may be due to reaction of the parent radical cation with pyridine. Iodine scavenging and quantum chemical calculations both show that the ortho-pyridyl radical (2-pyridyl) is far more stable than the other two isomers.