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Reaction of hydrogen atoms with propyne at high temperatures: An experimental and theoretical study

Bentz, T. and Giri, B. R. and Hippler, H. and Olzmann, M. and Striebel, F. and Szőri, Milán (2007) Reaction of hydrogen atoms with propyne at high temperatures: An experimental and theoretical study. JOURNAL OF PHYSICAL CHEMISTRY A, 111 (19). pp. 3812-3818. ISSN 1089-5639

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Abstract

The kinetics of the reaction of hydrogen atoms with propyne (pC(3)H(4)) was experimentally studied in a shock tube at temperatures ranging from 1200 to 1400 K and pressures between 1.3 and 4.0 bar with Ar as the bath gas. The hydrogen atoms (initial mole fraction 0.5-2.0 ppm) were produced by pyrolysis of C(2)H(5)I and monitored by atomic resonance absorption spectrometry under pseudo-first-order conditions with respect to propyne (initial mole fraction 5-20 ppm). From the hydrogen atom time profiles, overall rate coefficients k(ov) equivalent to -([pC(3)H(4)][H])(-1) x d[H]/dt for the reaction H + pC(3)H(4) -> products (not equal H) were deduced; the following temperature dependence was obtained: k(ov) = 1.2 x 10(-10) exp(-2270 K/T) cm(3) s(-1) with an estimated uncertainty of +/- 20%. A pressure dependence was not observed. The results are analyzed in terms of statistical rate theory with molecular and transition state data from quantum chemical calculations. Geometries were optimized using density functional theory at the B3LYP/6-31G(d) level, and single-point energies were computed at the QCISD(T)/cc-pVTZ level of theory. It is confirmed that the reaction proceeds via an addition-elimination mechanism to yield C(2)H(2) + CH(3) and via a parallel direct abstraction to give C(3)H(3) + H(2). Furthermore, it is shown that a hydrogen atom catalyzed isomerization channel to allene (aC(3)H(4)), H + pC(3)H(4) -> aC(3)H(4) + H, is also important. Kinetic parameters to describe the channel branching of these reactions are deduced.

Item Type: Article
Subjects: Q Science / természettudomány > QD Chemistry / kémia > QD02 Physical chemistry / fizikai kémia
SWORD Depositor: MTMT SWORD
Depositing User: MTMT SWORD
Date Deposited: 01 Oct 2017 16:22
Last Modified: 01 Oct 2017 16:22
URI: http://real.mtak.hu/id/eprint/64602

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