KINETICS OF THE GAS-PHASE REACTION OF OH WITH CLNO2 FROM 259-K TO 348-K
Journal of Physical Chemistry, 96 (6):
2568--2572 (January 1992)Abstract
The temperature dependence of the rate constant for the gas-phase reaction of OH with ClNO2 has been determined from 259 to 348 K using a fast flow discharge system. The decay of OH was followed using resonance fluorescence in the presence of a great excess of ClNO2. Two different flow tube wall coatings, phosphoric acid and halocarbon wax, were used to check for possible heterogeneous reactions. The rate constant over this temperature range can be expressed in the Arrhenius form k = (2.4(-1.1)+1.4) x 10(-12) exp(-1250 +/- 155)/T cm3 molecule-1 s-1, where the uncertainties are two standard deviations and represent precision only. Systematic errors due to the presence of small amounts of impurities Cl2 and ClNO could introduce an additional 10% uncertainty into the A factor and 5% into the value of E(a)/R. The sole chlorine-containing product, observed by mass spectrometry, from 298 to 348 K was HOCl. Both this product and the kinetics are consistent with the existence of one major (> 90%) product channel, OH + ClNO2 --> HOCl + NO2. The kinetics and mechanism of this reaction are compared to those of the reactions of OH with nitrosyl chloride (ClNO) and chlorine nitrate (ClONO2). This reaction of OH with ClNO2 is sufficiently slow that photolysis will be the major fate of ClNO2 in the troposphere.