title: Spectroscopic studies on the photochemical decarboxylation mechanisms of synthetic pyrethroids.
abstract: A novel radical trapping technique combined with a fluorescence spectroscopic analysis has been employed to investigate the radical intermediates produced by photodecarboxylation of four synthetic pyrethroids: fenvalerate (SMD), fenpropathrin (DTL), cyphenothrin (GKL), and cypermethrin (AGT). Under photoirradiation at >290 nm, all pyrethroids underwent direct photolysis via homolytic cleavage of the carbon-oxygen bonds in the ester groups. The consumed amount of a nitroxide free radical, as a trapping agent for the intermediate radical of a pyrethroid, was determined by ESR, which was the measure of the reaction yield of a photochemically generated α-cyano-3-phenoxybenzyl radical common to all pyrethroids. The reactivities of the pyrethroids studied was in the sequence of SMD >> DTL > GKL > AGT. Furthermore, nanosecond transient absorption spectroscopy demonstrated that geminate recombination of the radical pair within a solvent cage is the main deactivation route of the photochemically generated α-cyano-3-phenoxybenzyl radical common for all pyrethroids studied.
authors.affiliation: Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd, Takarazuka, Hyogo, Japan. suzukiy16@sc.sumitomo-chem.co.jp
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Shoji
authors.initials: S
authors.lastname: Ishizaka
authors.forename: Noboru
authors.initials: N
authors.lastname: Kitamura
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000737:chemistry; D009570:Nitriles / Q000737:chemistry; D010782:Photolysis; D011722:Pyrethrins / Q000138:chemical synthesis / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D005609:Free Radicals; D009570:Nitriles; D011722:Pyrethrins; C017160:cypermethrin; C044267:fenpropathrin; C051001:cyphenothrin; C017690:fenvalerate