14N and 1H ENDOR studies of x-irradiated single crystals of hippuric acid

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Abstract
N‐benzoylaminomethyl radical formed by room temperature x‐irradiation of single crystals of hippuric acid (N‐benzoylglycine) has been identified and its structure established by detailed ENDOR studies at 77 K. Besides proton signals, ENDOR transitions arising from the hyperfine and quadrupole interactions of the 14N nucleus were also detected and a detailed analysis is presented. The assignment of exchangeable protons has been accomplished by use of partially deuterated crystals. Radical identification and spin density distribution have been confirmed by comparison of the experimental results with those obtained from INDO–MO calculations. The radical is most likely formed from oxidized hippuric acid by deprotonation and subsequent decarboxylation.