Reaction Kinetics of PO2Cl-, PO2Cl2 -, POCl2 -, and POCl3 - with O2 and O3 from 163 to 400 K

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 108; no. 42; pp. 9120 - 9125
• Main Authors: Fernandez, Abel I, Midey, Anthony J, Miller, Thomas M, Viggiano, A. A
• Format: Journal Article
• Language: English
• Published: American Chemical Society 21.10.2004
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp047545q

Rate constants and product ion branching fractions for the gas-phase reactions of O2 and O3 with the anions (a) PO2Cl-, (b) POCl3 -, (c) POCl2 -, and (d) PO2Cl2 - were measured in a selected-ion flow tube (SIFT). The kinetics were measured at temperatures of 163−400 K and a He pressure of 0.4 Torr. Only PO2Cl- reacts with O2 to a measurable extent, having k(163−400 K) = 1.1 × 10-8(T/K)-1.0 cm3 molecule-1 s-1, while O3 reacts with all of the anions except PO2Cl2 -. The fitted rate constant expressions for the O3 reaction with anions a−c are as follows:  k a(163−400 K) = 3.5 × 10-6(T/K)-1.6, k b(163−400 K) = 4.0 × 10-7(T/K)-1.2, and k c(163−400 K) = 3.7 × 10-7(T/K)-1.4 cm3 molecule-1 s-1. Calculations were performed at the G3 level of theory to obtain optimized geometries, energies, and electron affinities (EAs) of the reactant and product species, as well as to determine the reaction thermochemistry to help understand the experimental results. The PO x Cl y - anions that have lower electron binding energies (eBE) and higher spin multiplicities are more reactive. The doublets are more labile than the singlets. How the extra electron density is distributed in the anion does not predict the observed reactivity of the ion. The reactions of PO2Cl- with O2 and O3 yield predominantly PO3 - and PO4 -. The reaction of POCl2 - with O3 yields mostly Cl- and PO2Cl2 -, while the POCl3 - reaction with O3 yields mostly O3 - and PO2Cl2 -.