ESR Study of Stereospecific Proton Transfer in Irradiated Crystals of l-Alanine

Crystals of l-alanine irradiated at 80°K were studied with ESR technique. It was found that the proton transfer, which had originally been proposed by Sinclair and Hanna, was stereospecific: The produced species was found to be O(1)−/CH3HCNH3+—Ċ(2)–H, and no evidence for its chemically equivalent species O(1)–H/CH3HCNH3+—Ċ(2)− was detected. This stereospecific proton transfer was interpreted on the basis of a quantum-tunneling model, which was found to account for the observed result satisfactorily. A new sample cavity was developed. This cavity has a device which enables one to orient an irradiated crystal to any desired direction, even at 80°K.