An electron spin resonance study of γ-irradiated lithium DL-lactate

Abstract

An e.s.r. study of single crystals of lithium DL-lactate, irradiated at room temperature, indicates that the free radical CH₃C(OH)CO₂-Li⁺ is trapped in the crystalline matrix and from the magnitude of the isotropic hyperfine splitting parameters of the methyl protons (53.0 MHz) and the hydroxyl group (9.3 MHz),it is inferred that extensive polarization of the orbital containing the unpaired electron into the carboxylate and hydroxyl groups occurs. Experiments on powdered lithium DL-lactate show that this free radical is formed at the end of a reaction sequence. When lithium DL-lactate is irradiated at 77ºK, the low temperature e.s.r. pattern originates from CH₃CHCO₂-Li⁺ and it is only on warming the sample that the fragment CH₃C(OH)CO₂-Li⁺ is formed. A similar reaction sequence has also been noted in irradiated glycollic acid.