title: Gas-phase reactivity of the O=P(OCH3)2 + phosphonium ion towards alpha,beta-unsaturated esters in a quadrupole ion trap.
abstract: Ion-molecule reactions between the O=P(OCH3)2 + phosphonium ions and eight alpha,beta-unsaturated esters (methyl acrylate, ethyl acrylate, methyl crotonate, ethyl crotonate, methyl 3,3-dimethylacrylate, ethyl 3,3-dimethylacrylate, methyl methacrylate and ethyl methacrylate) were performed in a quadrupole ion trap mass spectrometer. The O=P(OCH3)2 + phosphonium ions, formed by electron ionization from neutral trimethyl phosphite, were found to react with alpha,beta-unsaturated esters to give an adduct [RR'C=CR''COOR''', O=P(OCH3)2]+, which lose spontaneously a molecule of trimethyl phosphate (R'''=CH3) or dimethyl ethyl phosphate (R'''=C2H5). An ion corresponding to a protonated trialkyl phosphate is also observed when substituent R''=H. To confirm the experimental results, and to elucidate the mechanism for the formation of the ionic species, a theoretical study using the density functional theory (DFT) approach was carried out. The potential energy surface obtained from B3LYP/6-31G(d,p) calculations for the reaction between O=P(OCH3)2 + and methyl acrylate is described.
authors.affiliation: Laboratoire Analyse et Environnement, CNRS UMR 8587, Université d'Evry Val-d'Essonne, Bd François Mitterrand, 91025 Evry Cedex, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Leclerc
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Leon
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Taphanel
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Morizur