OH REACTION-KINETICS OF POLYCYCLIC AROMATIC-HYDROCARBONS AND POLYCHLORINATED DIBENZO-P-DIOXINS AND DIBENZOFURANS

Rate constants were measured for gas-phase reactions of the hydroxyl r adical (OH) with six polycyclic aromatic hydrocarbons (PAH) and four p olychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F). These OH reaction rate constants were determined in helium at about 1 atm over various temperature ranges between 306 and 405 K. The experiments were carried out in a small, heated quartz reaction chamber sampled by on- line mass spectrometry, and OH was produced by the photolysis of O-3 i n the presence of H2O. Arrhenius regressions were performed with the r ate constants of each compound, and the temperature dependencies were found to be slight to nonexistent. The OH reaction rate constants of P CDD/F were in agreement with those predicted by a structure-reactivity method. The resulting rate constants at 298 K (in units of 10(-12) cm (3) s(-1)) were as follows: naphthalene, 23; acenaphthene, 58; fluoren e, 13; phenanthrene, 27; anthracene, 190; fluoranthene, 11; dibenzo-p- dioxin, 12; 2,7-dichlorodibenzo-p-dioxin, 4.4; dibenzofuran, 3.5; and 2,8-dichlorodibenzofuran, 2.2.