title: Gas-phase reactivity of the O=P(OCH3)2+ phosphonium ion with aliphatic esters in a quadrupole ion trap. Spontaneous elimination of ketenes.
abstract: Ion-molecule reactions between the O=P(OCH(3))(2) (+) phosphonium ions and five aliphatic esters (methyl acetate, methyl propionate, methyl 2-methylpropionate, methyl butyrate and ethyl acetate) were performed in a quadrupole ion trap mass spectrometer. The O=P(OCH(3))(2) (+) phosphonium ions, formed by electron ionization from neutral trimethyl phosphite, were found to react with aliphatic esters to give an adduct ion [RR'CHCOOR", O=P(OCH(3))(2)](+), which loses spontaneously a molecule of ketene CH(2)=CO or substituted ketenes RR'C=CO. Isotope-labeled methyl acetate was used to elucidate fragmentation mechanisms. The potential energy surface obtained from B3LYP/6-31G(d,p) calculations for the reaction between O=P(OCH(3))(2) (+) and methyl acetate 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: Marie-Hélène
authors.initials: MH
authors.lastname: Taphanel
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Morizur