title: Gas phase kinetics and equilibrium of allyl radical reactions with NO and NO2.
abstract: Allyl radical reactions with NO and NO(2) were studied in direct, time-resolved experiments in a temperature controlled tubular flow reactor connected to a laser photolysis/photoionization mass spectrometer (LP-PIMS). In the C(3)H(5) + NO reaction  1 , a dependence on the bath gas density was observed in the determined rate coefficients and pressure falloff parametrizations were performed. The obtained rate coefficients vary between 0.30-14.2 × 10(-12) cm(3) s(-1) (T = 188-363 K, p = 0.39-23.78 Torr He) and possess a negative temperature dependence. The rate coefficients of the C(3)H(5) + NO(2) reaction  2  did not show a dependence on the bath gas density in the range used (p = 0.47-3.38 Torr, T = 201-363 K), and they can be expressed as a function of temperature with k(C(3)H(5) + NO(2)) = (3.97 ± 0.84) × 10(-11) × (T/300 K) (-1.55±0.05) cm(3) s(-1). In the C(3)H(5) + NO reaction, above 410 K the observed C(3)H(5) radical signal did not decay to the signal background, indicating equilibrium between C(3)H(5) + NO and C(3)H(5)NO. This allowed the C(3)H(5) + NO ⇄ C(3)H(5)NO equilibrium to be studied and the equilibrium constants of the reaction between 414 and 500 K to be determined. With the standard second- and third-law analysis, the enthalpy and entropy of the C(3)H(5) + NO ⇄ C(3)H(5)NO reaction were obtained. Combined with the calculated standard entropy of reaction (ΔS°(298) = 137.2 J mol(-1)K(-1)), the third-law analysis resulted in ΔH°(298) = 102.4 ± 3.2 kJ mol(-1) for the C(3)H(5)-NO bond dissociation enthalpy.
authors: Laboratory of Physical Chemistry, Department of Chemistry, University of Helsinki, P.O. Box 55 (A.I. Virtasen aukio 1), FIN-00014 Helsinki, Finland. matti.p.rissanen@helsinki.fi
authors: Matti P
authors: MP
authors: Rissanen
authors: Damien
authors: D
authors: Amedro
authors: Lev
authors: L
authors: Krasnoperov
authors: Paul
authors: P
authors: Marshall
authors: Raimo S
authors: RS
authors: Timonen
mesh_terms: D000498:Allyl Compounds / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry; D005740:Gases / Q000737:chemistry; D007700:Kinetics; D009569:Nitric Oxide / Q000737:chemistry*; D009585:Nitrogen Dioxide / Q000737:chemistry*; D013696:Temperature
chemical_list: D000498:Allyl Compounds; D005609:Free Radicals; D005740:Gases; D009569:Nitric Oxide; D009585:Nitrogen Dioxide