A Shock Tube Study of H + HNCO + NH 2 + CO

The reaction of atomic hydrogen with isocyanic acid (HNCO) to produce the amidogen radical (NHZ) and carbon monoxide, (W)) H + HNCO NH2 + CO has been studied in shock-heated mixtures of HNCO dilute in argon. Time-histories of the ground-state NHZ radical were measured behind reflected shock waves using cw, narrowlinewidth laser absorption at 597 nm, and HNCO time-histories were measured using infrared emission from the fundamental u2-band of HNCO near 5 pm. The second-order rate coefficient of reaction (2(a)) was determined to be: kZn = 2.1 x 1014 exp(-8500/T,K) ( f = 0.5, F = 1.75) T = 2340-3270 K , cm3 mol-’ s-’, where f and F define the lower and upper uncertainty limits, respectively. An upper limit on the rate coefficient of (5) NH2 + HNCO + NH3 + NCO was determined to be: k s 5 5.0 x 10” cm3 mol-’ s-’, T = 2340-2680 K