ESR study of some gamma irradiated amino acids and condensed 1,4-dihydropyridines

L-alanine methyl ester hydrochloride, 2-aminoisobutyric acid and some condensed 1,4-dihydropyridine derivatives (Compounds R1–R4) were gamma irradiated, the induced free radicals was investigated at room temperature by electron spin resonance techniques. The observed paramagnetic species of amino acids compounds were attributed to the CH3ĊHCOOCH3 and (CH3)2ĊCOOH radicals, respectively. The observed spectra of the 1,4-dihydropyridine derivatives interpreted in terms of some type of amine radical fragments. The spectra were computer simulated and the g values of the radicals and the hyperfine structure constants of the unpaired electron with nearby protons and 14N nucleus were determined. In this study, the observed paramagnetic species were found to be stable at room temperature more than 2 months.