Theoretical and Shock Tube Study of the Rate Constants for Hydrogen Abstraction Reactions of Ethyl Formate

Abstract

We report a systematic chemical kinetics study of the H atom abstractions from ethyl formate (EF) by H, O(P), CH, OH, and HO radicals. The geometry optimization and frequency calculation of all the species were conducted using the M06 method and the cc-pVTZ basis set. The one-dimensional hindered rotor treatment of the reactants and transition states and the intrinsic reaction coordinate analysis were also performed at the M06/cc-pVTZ level of theory. The relative electronic energies were calculated at the CCSD(T)/cc-pVXZ (where X = D, T) level of theory and further extrapolated to the complete basis set limit. Rate constants for the tittle reactions were calculated over the temperature range 500-2500 K by the transition state theory (TST) in conjunction with the asymmetric Eckart tunneling effect. In addition, the rate constants of H-abstraction by hydroxyl radical were measured in shock tube experiments at 900-1321 K and 1.4-2.0 atm. Our theoretical rate constants of OH + EF → products agree well with the experimental results within 15% over the experimental temperature range of 900-1321 K. Branching ratios for the five types of H-abstraction reactions were also determined from their individual site-specific rate constants.

Reaction Mechanisms and Kinetics of the Hydrogen Abstraction Reactions of C4–C6 Alkenes with Hydroxyl Radical: A Theoretical Exploration

“…To this end, it was necessary to include the contribution of RComps and PComps to the rate constant. However, a series of previous theoretical studies indicated that the formation of the RComps was not the rate-determining step [21,22,23]. Such a simplification is rational in kinetics because the energies of the formed weakly RComps are just lower than the reactants, as shown in Figure 3, and are rather unstable at high temperatures.…”

A theoretical and shock tube kinetic study on hydrogen abstraction from phenyl formate

“…TS3 and TS4 have one H-bond (2.546 and 2.538 Å) and the OH radical is perpendicular to the benzene ring plane. Compared with the TSs of other methyl esters (MF, 4 MA, 5 MP 6 and EF 26 ) that have H-bond lengths of 1.970-2.220 Å, the influence of Hbond on the energies of PF is not as obvious as the alkyl esters due to the longer H-bond. For the PF + HO2 reactions, all the four TSs are stabilized by the H-bond formed between the carbonyl oxygen and H-atom in the benzene ring.…”

“…Note that the Eckart tunneling correction is not applicable for certain reaction channels with negative energy barriers (see Table S1). Thus, the Winger method 25 was used instead to account for the tunneling effect as the deviation between the Eckart and Winger corrections is only 6−20% over the temperature range of 500−2500 K. 26 As no relevant experimental and theoretical results were reported in the literature, Fig. 2 only presents the rate constants for PF + H determined in this work.…”

“…Fig. 6 compares the rate constants for H-abstractions Please do not adjust margins Please do not adjust margins from MF, 4 ethyl formate (EF), 26 benzene, 28 toluene 28 and PF by OH. Comparing the H-abstraction at the carbonyl site from MF, EF and PF, reaction (PF + OH) has the largest rate constant, followed by reactions (EF + OH) and (MF + OH) shown in Fig.…”

Small ester combustion chemistry: Computational kinetics and experimental study of methyl acetate and ethyl acetate

“…H-atom abstractions from all three sites on EA by ȮH and HȮ2 radicals were calculated in this work. The rates for H-atom abstraction on the ethyl side by radicals other than ȮH/HȮ2 radicals were assumed to be similar to the rates reported by Wu et al [28], which were calculated for ethyl formate. They were adopted here because of the partial structural similarity to EA, and because no other studies have reported these rates for EA.…”