Elementary reaction

About: Elementary reaction is a research topic. Over the lifetime, 2972 publications have been published within this topic receiving 76110 citations.

Catalytic effect of a single water molecule on the atmospheric reaction of HO2 + OH: fact or fiction? A mechanistic and kinetic study

Abstract: The catalytic effect of a single water molecule was investigated by studying the reaction of HO2 with OH at the CCSD(T)/aug-cc-pVTZ//CCSD/6-311G(d,p) level of theory. Three hydrogen abstraction channels were found for the reaction of HO2 with OH in the absence of a water molecule. The reaction channel for 3O2 formation was dominant. The computed rate constant for the reaction was 2.2 × 10−11 cm3 molecule−1 s−1 at 298 K and was in good agreement with previously reported values. In the presence of a water molecule, the two reactions of the complex HO⋯H2O with HO2 and the complex HO2⋯H2O with OH were investigated. The calculated results show that the reaction mechanisms become much more complex, but the dominant product does not change. Although a water molecule plays a role in the positive catalytic effect of decreasing the energy of the transition state barrier within the temperature range of 216.7–298.2 K, the effective rate constants of HO2⋯H2O + OH and HO2 + HO⋯H2O reactions are respectively slower by 5–9 and 2–3 orders of magnitude than that of the unassisted reaction in the absence of a water molecule. Thus, we can predict that the title reaction’s rate enhancement by a single water molecule does not occur under tropospheric conditions.

The reaction of F + D2 at ultra-low temperatures: the effect of rotational excitation

Abstract: We report an ab initio study of the dynamics of the reaction F + D2→DF + D, where D2 is initially in a rotationally excited state (j = 2). The possibility of obtaining ultra-cold molecules and of investigating reaction dynamics at ultra-low temperature relies on the production of molecules in a well defined quantum state and it is important to know the relative efficiency of the rotational quenching and of the chemical reaction. We examine here a reaction with an activation barrier, the reaction of F with D2, and we find that quenching dominates the reaction when the initial rotational level lies energetically below the barrier, so severe trap loss may occur before the reaction can take place.

Kinetics of the Reactions of CH2(ã1A1) with CH3C2H, HCN, CO2, N2O and COS

Abstract: The reactions of CH2(a1A1) with CH3C2H, HCN, CO2, N2O and COS are investigated at room temperature. CH2(a1A1) is generated by pulsed laser photolysis of CH2CO. Overall removal rate constants are derived from concentration profiles under first order reaction conditions using direct, time resolved LIF detection of CH2(a1A1). The second order rate constants are found in units of 1013 cm2/mol s to be 24, 18, 2.0, 3.8 and 20, respectively. — The contributions of physical quenching to the removal of CH2(a1A1) are determined by monitoring directly the formation of CH2(X3B1) with the LMR absorption technique. The branching ratios of collision induced intersystem crossing versus total consumption of 1CH2 are 0.24, 0.32, 0.67, 0.46 and 0.29 for the five reactants.