title: Scavenging of dpph* radicals by vitamin E is accelerated by its partial ionization: the role of sequential proton loss electron transfer.
abstract: [reaction: see text] Rate constants for reaction of alpha-tocopherol, 2,2,5,7,8-pentamethyl-6-hydroxychroman, and 2,6-di-tert-butyl-4-methylphenol with 2,2-diphenyl-1-picrylhydrazyl radical were measured in solvents of different polarity and H-bond basicity. In ionization supporting solvents besides hydrogen atom transfer (HAT), the kinetics of the process is partially governed by sequential proton loss electron transfer (SPLET). Addition of acetic acid reduces the rate by eliminating SPLET to leave only HAT, while addition of water increases the rate by enhancing phenol deprotonation.
authors.affiliation: Warsaw University, Department of Chemistry, Warsaw, Poland.
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Musialik
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Litwinienko
mesh_terms: D000975:Antioxidants / Q000737:chemistry / Q000494:pharmacology; D001713:Biphenyl Compounds; D004583:Electrons; D016166:Free Radical Scavengers / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry / Q000494:pharmacology; D010851:Picrates / Q000737:chemistry*; D011522:Protons; D014810:Vitamin E / Q000737:chemistry* / Q000494:pharmacology
chemical_list: D000975:Antioxidants; D001713:Biphenyl Compounds; D016166:Free Radical Scavengers; D010636:Phenols; D010851:Picrates; D011522:Protons; D014810:Vitamin E; C004931:1,1-diphenyl-2-picrylhydrazyl