Atmospheric Gas-Phase Reactions of Selected Phosphorus-Containing Compounds

The kinetics of the gas-phase reactions of phosphorus oxychloride [P(O)Cl 3 ], methylphosphonic dichloride [CH 3 P(O)Cl 2 ], dimethyl phosphonate [(CH 3 O) 2 P(O)H], and trimethyl phosphite [(CH 3 O) 3 P] with the OH radical were measured at 298 ± 2 K and 1 atm (∼740 Torr) of dry air by a relative rate method which employed the photolysis of CH 3 ONO as the source of OH radicals and analysis of the reaction mixtures by in-situ Fourier transform infrared (FT-IR) spectroscopy. The measured values of the OH radical reaction rate constants (cm 3 molecule -1 s -1 ) are the following: P(O)Cl 3, < 4 × 10 -14; CH 3 P(O)Cl 2, (6.4 ± 2.1) × 10 -14; (CH 3 O) 2 P(O)H, (5.08 ± 0.53) × 10 -12; and (CH 3 O) 3 P, (7.1 ± 0.9) × 10 -10, corresponding to estimated tropospheric lifetimes of >290 days, 180 days, 2.3 days, and 0.016 day, respectively, for the reactions of these compounds with OH radicals. In support of the OH radical rate constant measurement for (CH 3 O) 3 P, the absolute rate constant for the NO 2 + (CH 3 O) 3 P reaction was measured and determined to be (3.8 ± 0.4) × 10 -18 cm 3 molecule -1 s -1 at 298 ± 2 K. The products of the reaction of dimethyl phosphonate with the OH radical and those of trimethyl phosphite with the OH radical, NO 2, and O 3 were investigated by FT-IR spectroscopy and atmospheric pressure ionization mass spectrometry (API-MS).