ESR STUDY OF L-ALANINE-1-13C IRRADIATED AT LOW TEMPERATURES

The ESR spectra of L-alanine-l-uC, x irradiated at low temperatures (T<150°K.), have been examined. The spectra have been interpreted in terms of a carboxyl radical similar to those postulated for other irradiated organic acids. From the values of the 12C hyperfine tensor it has been confirmed that the unpaired electron is essentially a 2pr-type electron located primarily on the carboxyl carbon and that this spin density interacts with the a proton. From the magnitude of the isotropic 13C hyperfine splitting it is found that the RCO2 - structure is bent about 8° from planarity. The stable room-temperature fragment in irradiated L-alanine-l-18C ejdiibits essentially isotropic 18C splittings of 12.8 G.