On the Kinetics of Reactions of Hydrogen Atoms with Aromatic Hydrocarbons

Triebert, J.; Engelmann, L.; Olzmann, Matthias; Scherzer, K.

doi:10.1524/zpch.1998.205.part_1.033

Cited by 7 publications

(8 citation statements)

References 21 publications

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“…The present k 1 data are in excellent accord with the results of Nicovich and Ravishankara 21 below 500 K (see Figure 4), and the greatest difference is less than 5%. The 298 K value of Triebert et al 28 of (5.6 ( 2.8) × 10 -14 cm 3 molecule -1 s -1 is also in agreement. This latter measurement extends the pressure range for the bath gas down to 4 mbar of He, so reaction 1 does appear to be at the high-pressure limit under our conditions, as argued previously by Nicovich and Ravishankara.…”

Section: Resultssupporting

confidence: 78%

“…21 However, Mebel et al have since suggested that secondary chemistry could have been important under the conditions employed. 27 One measurement has appeared subsequently by Triebert et al 28 Here we reinvestigate reaction 1 and its reverse, reaction -1, by the laser flash-photolysis/resonance fluorescence (LP-RF) technique and use the ratio of the rate constants to derive the equilibrium constant for reaction 1 and thus its thermochemistry.…”

Section: Introductionmentioning

confidence: 99%

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Enthalpy of Formation of the Cyclohexadienyl Radical and the C−H Bond Enthalpy of 1,4-Cyclohexadiene: An Experimental and Computational Re-Evaluation

et al. 2009

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A quantitative understanding of the thermochemistry of cyclohexadienyl radical and 1,4-cyclohexadiene is beneficial for diverse areas of chemistry. Given the interest in these two species, it is surprising that more detailed thermodynamic data concerning the homolytic C-H bond enthalpies of such entities have not been forthcoming. We thus undertook an experimental and computational evaluation of (a) the enthalpy of formation of cyclohexadienyl radical (C 6 H 7 ), (b) the homolytic C-H bond enthalpy of 1,4-cyclohexadiene (C 6 H 8 ), and (c) the enthalpy of the addition of a hydrogen atom to benzene. Using laser photolysis experiments coupled with highly accurate ab initio quantum mechanical techniques, a newly recommended enthalpy of formation for C 6 H 7 is determined to be 208.0 ( 3.9 kJ mol -1 , leading to a homolytic bond dissociation enthalpy of 321.7 ( 2.9 kJ mol -1 , almost 9 kJ mol -1 higher than previously determined enthalpies that used less certain experimental values for the C 6 H 7 enthalpy of formation.

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Section: Resultssupporting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Enthalpy of Formation of the Cyclohexadienyl Radical and the C−H Bond Enthalpy of 1,4-Cyclohexadiene: An Experimental and Computational Re-Evaluation

et al. 2009

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“…The temperatureindependent rates from LPSB01 for addition to cations are used, which are based primarily on experimental work by Snow et al (1998). Addition to neutrals is about two orders of magnitude slower for benzene (Triebert et al 1998;Mebel et al 1997) and has not been measured for larger PAHs. No rates are known for the addition of hydrogen to anions or to cations with Z > 1.…”

Section: Hydrogen Additionmentioning

confidence: 99%

PAH chemistry and IR emission from circumstellar disks

Visser¹,

Geers²,

Dullemond

et al. 2007

A&A

100

127

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Aims. The chemistry of, and infrared (IR) emission from, polycyclic aromatic hydrocarbons (PAHs) in disks around Herbig Ae/Be and T Tauri stars are investigated. PAHs can exist in different charge states and they can bear different numbers of hydrogen atoms. The equilibrium (steady-state) distribution over all possible charge/hydrogenation states depends on the size and shape of the PAHs and on the physical properties of the star and surrounding disk. Methods. A chemistry model is created to calculate the equilibrium charge/hydrogenation distribution. Destruction of PAHs by ultraviolet (UV) photons, possibly in multi-photon absorption events, is taken into account. The chemistry model is coupled to a radiative transfer code to provide the physical parameters and to combine the PAH emission with the spectral energy distribution (SED) from the star+disk system. Results. Normally hydrogenated PAHs in Herbig Ae/Be disks account for most of the observed PAH emission, with neutral and positively ionized species contributing in roughly equal amounts. Close to the midplane, the PAHs are more strongly hydrogenated and negatively ionized, but these species do not contribute to the overall emission because of the low UV/optical flux deep inside the disk. PAHs of 50 carbon atoms are destroyed out to 100 AU in the disk's surface layer, and the resulting spatial extent of the emission does not agree well with observations. Rather, PAHs of about 100 carbon atoms or more are predicted to cause most of the observed emission. The emission is extended on a scale similar to that of the size of the disk, with the short-wavelength features less extended than the long-wavelength features. For similar wavelengths, the continuum emission is less extended than the PAH emission. Furthermore, the emission from T Tauri disks is much weaker and concentrated more towards the central star than that from Herbig Ae/Be disks. Positively ionized PAHs are predicted to be largely absent in T Tauri disks because of the weaker radiation field.

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“…Calvert et al (2002) b. Bohn (2001 j. Atkinson (1986) r. Atkinson et al (1984) c. Atkinson and Aschmann (1989) k. Corchnoy and Atkinson (1990) s. Bolzacchini et al (1999) d. Atkinson and Aschmann (1988) l. Baulch et al (1994) t. Triebert et al (1998) e. Bignozzi et al (1981 m. Frerichs et al (1989) u. Baulch et al (1992) f. Chiorboli et al (1983) n. Cvetanovic (1987) v. Shi and Bernhard (1997) g. Kwok et al (1997) o.…”

Section: Methodsmentioning

confidence: 99%

Predicting arene rate coefficients with respect to hydroxyl and other free radicals in the gas-phase: a simple and effective method using a single topological descriptor

et al. 2007

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Abstract. The reactivity of aromatic compounds is of great relevance to pure and applied chemical disciplines, yet existing methods for estimating gas-phase rate coefficients for their reactions with free radicals lack accuracy and universality. Here a novel approach is taken, whereby strong relationships between rate coefficients of aromatic hydrocarbons and a Randić-type topological index are investigated, optimized and developed into a method which requires no specialist software or computing power.Measured gas-phase rate coefficients for the reaction of aromatic hydrocarbons with OH radicals were correlated with a calculated Randić-type index, and optimized by including a term for side chain length. Although this method is exclusively for use with hydrocarbons, it is more diverse than any single existing methodology since it incorporates alkenylbenzenes into correlations, and can be extended towards other radical species such as O( 3 P ) (and tentatively NO 3 , H and Cl). A comparison (with species common to both techniques) is made between the topological approach advocated here and a popular approach based on electrophilic subsituent constants, where it compares favourably.A modelling study was carried out to assess the impact of using estimated rate coefficients as opposed to measured data in an atmospheric model. The difference in model output was negligible for a range of NO x concentrations, which implies that this method has utility in complex chemical models.Strong relationships (e.g. for OH, R 2 =0.96) between seemingly diverse compounds including benzene, multisubstituted benzenes with saturated, unsaturated, aliphatic and cyclic substitutions and the nonbenzenoid aromatic, azuleneCorrespondence to: C. J. Percival (c.percival@manchester.ac.uk) suggests that the Randić-type index presented here represents a new and effective way of describing aromatic reactivity, based on a quantitative structure-activity relationship (QSAR).

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On the Kinetics of Reactions of Hydrogen Atoms with Aromatic Hydrocarbons

Cited by 7 publications

References 21 publications

Enthalpy of Formation of the Cyclohexadienyl Radical and the C−H Bond Enthalpy of 1,4-Cyclohexadiene: An Experimental and Computational Re-Evaluation

Enthalpy of Formation of the Cyclohexadienyl Radical and the C−H Bond Enthalpy of 1,4-Cyclohexadiene: An Experimental and Computational Re-Evaluation

PAH chemistry and IR emission from circumstellar disks

Predicting arene rate coefficients with respect to hydroxyl and other free radicals in the gas-phase: a simple and effective method using a single topological descriptor

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