title: Stopped-flow investigation of the reaction between vitamin E radical and vitamin C in solution.
abstract: Kinetic study of the reaction between vitamin E radical and vitamin C has been performed. The rates of reaction of vitamin C (ascorbic acid 1, 6-0-stearyl ascorbic acid 2, and 2,6-O-dipalmitoyl ascorbic acid 3) with vitamin E radical (5,7-diisopropyl-tocopheroxyl) in benzene-ethanol (2:1, v/v) solution have been determined spectrophotometrically, using stopped-flow technique. The second-order rate constants obtained are 549 +/- 30 M-1s-1 for 1, 626 +/- 53 M-1s-1 for 2, and 4.84 +/- 1.41 M-1s-1 for 3 at 25.0 degrees C. The result shows that the ascorbic acid ester 2 having a long-alkyl-chain at 6-position is 1.14 times as reactive as the ascorbic acid 1, whereas the ascorbic acid ester 3 substituted at 2-position is only 0.01 times as reactive as the ascorbic acid 1.
mesh_terms: D001205:Ascorbic Acid / Q000378:metabolism*; D005609:Free Radicals; D007700:Kinetics; D008433:Mathematics; D012996:Solutions; D014810:Vitamin E / Q000378:metabolism*
chemical_list: D005609:Free Radicals; D012996:Solutions; D014810:Vitamin E; D001205:Ascorbic Acid