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

The reaction of ?H 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 ?H radicals with the simplest amino acid glycine in the pH range studied.