Publication costs assisted by the Carnegie-Mellon University and the U. S, Atomic Energy Commission Radicals of the type RC(OH)COOR', produced by photoreduction of -keto acids and esters in 2-propanol solutions, have been studied by esr. In each of the five systems, glyoxylic acid, pyruvic acid, ketobutyric acid, methyl pyruvate, and ethyl pyruvate, the esr spectrum gave evidence for the existence of comparable concentrations of two different species interpreted as cis and trans isomers of the RC(OH)COOR' radicals. Accurate hyperfine constants are given for the pairs of isomers in all but the first case where resolution of the individual spectra was not possible.(1) Supported In part by the U. S. Atomic Energy Commission.(2) T.
The radicals produced by reaction of hydroxyl radicals with some amines, amino acids, and related compounds in aqueous solutions have been studied by esr. Irradiation with high-energy electrons was carried out directly in the esr cavity. In most cases amino alkyl radicals were formed by hydrogen abstraction from the carbon bearing the amino group. The radicals CH2NH2, CH2NHCH8, and CH2N (CH3)2 produced from mono-, di-, and trimethylamine have been observed in the pH range 7-13.5. In acid solutions no radicals with the expected structure RCHNH3+ have been observed. In the cases of diand trimethylammonium ions secondary reactions leading to radicals of the type R2ÑH+ take place. The radical found in acid solutions of glycine is best described by the structure NH2CHCOOH as supported by experiments in D20. In alkaline solutions of all amino acids radicals of the type H2NCRC02~were observed. In the case of -aminoisobutyric acid a different radical, probably of type RÑH, was also observed at pH 13 and low concentration of solute. The results are consistent with a mechanism involving the reaction RCH2NH3+ + H or OH RCHNH3+ + H2 or H20 in acid solution and the two competing reactions RCH2NH2 + OH -* RCHNH2 + H20 and RCH2-NH-2 + OH -RCH2ÑH + H20 in alkaline solution. The latter reaction must be followed by a fast secondary step, RCH2ÑH + RCH2NH2 RCH2NH2 + RCHNH2, whch causes the disappearance of RCH2ÑH in most cases.
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