Kinetics of the Reaction of Propargyl Radical with Nitric Oxide

Abstract

The reaction between the propargyl radical (C3H3) and NO has been investigated as a function of temperature (195−473 K) and pressure (3−100 Torr) by using color center laser infrared kinetic spectroscopy. At room temperature and below, the reaction rate was found to depend strongly on the helium buffer gas pressure and, at any fixed buffer gas density, to decrease with increasing temperature. This behavior is consistent with the reaction occurring by termolecular addition to produce C3H3NO. Data collected over a wide pressure range at 195 and 296 K were fitted to a semiempirical model developed by Troe for reactions of this type. The structure and energetics of the adduct were explored by performing both B3LYP 6-311++G(2df,2pd) and G2 calculations. The enthalpy change, ΔH, for addition of NO to the CH end of propargyl was determined as −123 and −138 kJ/mol, respectively, by using these two methods. The calculations also showed that NO can add at the CH2 end of propargyl but with a smaller binding energy. Estimates of the equilibrium constant for adduct formation, made using data obtained from these calculations, revealed that the addition reaction should shift from an equilibrium position strongly favoring the adduct to one strongly favoring free propargyl as the temperature is raised from 550 to 650 K. This temperature regime is higher than any of the temperatures reached experimentally.

Gas Phase Kinetics and Equilibrium of Allyl Radical Reactions with NO and NO2

“…The rate coefficients were observed to vary between 1.1 × 10 −12 and 1.5 × 10 −11 cm 3 s −1 , in comparison with 3.0 × 10 −13 to 1.4 × 10 −11 cm 3 s −1 determined for the C 3 H 5 + NO rate coefficients in the present study (p = 0.47−3.38 Torr, T = 201−363 K). DeSain et al 33 observed a strong dependence on bath gas pressure at 195 and 296 K and a negative temperature dependence of the rate coefficients through the temperature range used. According to their calculations, equilibrium between C 3 H 3 + NO and C 3 H 3 NO should be reached at about 500 to 650 K range, which was stated inaccessible due to experimental difficulties.…”

“…The qualitative behavior of the C 3 H 5 + NO reaction may be compared to that of the smallest resonantly stabilized hydrocarbon radicals' reaction with nitric oxide; C 3 H 3 + NO was investigated by DeSain et al 33 The C 3 H 3 + NO rate coefficients were measured at three temperatures, 195 K, 296 K, and 473 K, and at 2 to 100 Torr pressure of He using a color center laser infrared kinetic spectroscopy. The rate coefficients were observed to vary between 1.1 × 10 −12 and 1.5 × 10 −11 cm 3 s −1 , in comparison with 3.0 × 10 −13 to 1.4 × 10 −11 cm 3 s −1 determined for the C 3 H 5 + NO rate coefficients in the present study (p = 0.47−3.38 Torr, T = 201−363 K).…”

Radical reaction C3H+NO: A mechanistic study

“…Moreover, because both C 3 H (in linear and cyclic forms) and NO have been detected in space, the present efficient C 3 H+NO reaction might provide a mechanistic knowledge for understanding the depletion of both species in interstellar chemistry. We are aware that among the C 3 ‐radical chemistry,3–5 the simplest C 3 H has received the least attention concerning its reactivity despite its detection in space and its potential importance in hydrocarbon combustions. Reactions of the higher hydrogenated C 3 ‐radicals, that is, C 3 H 3 and C 3 H 5 , with NO have already been studied.…”

“…However, the chemistry of the C 3  HC radicals has been relatively little understood. Some experiments have been performed on the C 3 H 3 reactions with O 2 , O, NO, and C 2 H 2 3. The dimerization of C 3 H 5 and its reactions with NO, O‐atoms and HBr have already been experimentally studied 4.…”

“…The environmental nitric oxide (NO) is known to cause the acidification of rain, affect human health through ozone production, and product photochemical smog 12. The effectiveness in removal of NO (so‐called NO‐reburning) has been shown for a large number of radicals including the hydrocarbon radicals, CH n ( n = 1–3),1b–1f C 2 H n ( n =1,3)1g–1k, and C 3 H n ( n = 3,5) 3, 4b. However, the reaction between the simplest C 3 ‐radical, C 3 H, and NO has never been considered either experimentally or theoretically.…”