Studies on some radical transfer reactions by entrapping the radicals as polymer end groups. II. Reactions of ȮH radicals with amino acids

Abstract

AbstractThe reaction of ȮH radicals with a number of aliphatic amino acids has been studied by entrapping the resultant radicals as end groups of poly(methyl methacrylate) that have been detected and estimated by the sensitive dye partition technique. The rate constants of the reaction (in mol−1 L S−1) of 7 amino acids at 25°C and at pH 1.00 have been determined as 8.33 × 108 for glycine, 2.56 × 109 for β‐alanine, 2.01 × 109 for β‐alanine, 3.99 × 109 for 4‐amino butyric acid, 7.56 × 109 for (1+) valine, 1.42 × 1010 for (1−) leucine, and 5.98 × 1010 for 6‐amino caproic acid. Glycine, α‐alanine, β‐alanine, and 4‐amino butyric acid produced radicals that underwent deamination and incorporated only carboxyl‐bearing end groups in the polymer. The other amino acids, leucine, valine, and 6‐amino caproic acid, produced at least two types of radicals, radicals that underwent deamination and those that remained intact, and incorporated in the polymer both carboxyl‐ and amine‐bearing end groups but in different amounts. The latter type of radicals were about 29% from 6‐amino caproic acid, 23% from leucine, and 18% from valine. The change of pH from 0.80 to 2.72 did not produce any significant change in the end group profile of the polymer obtained, indicating no appreciable change in the rate of the reaction of ȮH radicals with the simplest amino acid glycine in the pH range studied.