Crossed-beam radical-radical reaction dynamics of O(P3)+C3H3→H(S2)+C3H2O

Abstract

The radical-radical oxidation reaction, O(3P)+C3H3 (propargyl)-->H(2S)+C3H2O (propynal), was investigated using vacuum-ultraviolet laser-induced fluorescence spectroscopy in a crossed-beam configuration, together with ab initio and statistical calculations. The barrierless addition of O(3P) to C3H3 is calculated to form energy-rich addition complexes on the lowest doublet potential energy surface, which subsequently undergo direct decomposition steps leading to the major reaction products, H+C3H(2)O (propynal). According to the nascent H-atom Doppler-profile analysis, the average translational energy of the products and the fraction of the average transitional energy to the total available energy were determined to be 5.09+/-0.36 kcal/mol and 0.077, respectively. On the basis of a comparison with statistical prior calculations, the reaction mechanism and the significant internal excitation of the polyatomic propynal product can be rationalized in terms of the formation of highly activated, short-lived addition-complex intermediates and the adiabaticity of the excess available energy along the reaction coordinate.

Hydrogen Atom Release Dynamics in Radical–Radical Reactions: Saturated vs Unsaturated

“…This was illustrated well by our crossed-beam investigations of Equations (1)-(2) of O( 3 P) with unsaturated p-conjugated radicals such as the allyl (C 3 H 5 ) and propargyl (C 3 H 3 ) radicals. [2][3][4] Oð 3 PÞ þ RH ðRH ¼ C 3 H 5 , C 3 H 3 Þ! Hð 2 SÞ þ OR ðmajorÞ ð1ÞIn these reactions, the hydrocarbon radicals were produced from a supersonic flash pyrolysis source, wherein the labile precursors underwent rapid, complete decomposition to generate jet-cooled radical beams without recombination and/or secondary dissociation.…”

“…This was illustrated well by our crossed-beam investigations of Equations (1)-(2) of O( 3 P) with unsaturated p-conjugated radicals such as the allyl (C 3 H 5 ) and propargyl (C 3 H 3 ) radicals. [2][3][4] Oð 3 PÞ þ RH ðRH ¼ C 3 H 5 , C 3 H 3 Þ! Hð 2 SÞ þ OR ðmajorÞ ð1Þ…”

A Theoretical Investigation of the Gas‐Phase Oxidation Reaction of the Saturated tert‐Butyl Radical

“…[16] As manifested in recent dynamics and theoretical investigations, the prediction of the major channels is also consistent with the gas-phase kinetic observations in the oxidation reactions of unsaturated hydrocarbon radicals such as allyl and propargyl. [3][4][5][6][7][8][9][10] The quantitative information of the kinetic rate constants and branching ratio can be described on the basis of the microcanonical statistical theory. .…”

“…[3][4][5][6][7][8][9][10] A supersonic flash pyrolysis source was adopted to produce clean, jet-cooled radical beams without experiencing recombination and/or secondary dissociation. [6] With the aid of quantum statistical calculations, analyses of the nascent state distributions of various reaction products have demonstrated the existence of unusual reaction mechanisms and dynamic characteristics in comparison to the predicted energy distributions.…”

Reaction Dynamics of Carbon‐Centered Radicals in Extreme Environments Studied by the Crossed Molecular Beam Technique

“…[104][105][106][107][108] Due to the experimental difficulties in generating two unstable reactants simultaneously, only a very few atom-radical reactions have been conducted so far under single collision conditions. These are reactions of ground-state carbon atoms with propargyl by the PI 109 and of oxygen atoms with t-butyl (t-C 4 H 9 ), 110 propargyl, 111,112 and allyl (C 3 H 5 ). 113,114 However, the detection of the products of the oxygen atom reactions was limited to those with well-established fingerprints using LIF of the hydroxyl (OH) radical product formed in the hydrogen abstraction channel and of atomic hydrogen using hydrogen atom Doppler profile analysis.…”