Master Equation Modeling of the Unimolecular Decompositions of α‐Hydroxyethyl (CH₃CHOH) and Ethoxy (CH₃CH₂O) Radicals

Abstract

The unimolecular decomposition of two radical isomers of C2H5O (CH3CH2O/ethoxy, CH3CHOH/α‐hydroxyethyl) are investigated by means of Rice–Ramsperger–Kassel–Marcus/master equation simulations in helium and nitrogen bath gases on an accurate one‐dimensional potential energy surface. For ethoxy, simulations are carried out between temperatures of 406 and 1200 K and pressures of 0.001 and 100 atm. For CH3CHOH, simulations are carried out between temperatures of 800 and 1500 K and pressures of 0.001 and 100 atm. Results are compared with available experimental data, with good agreement. The dominant product of α‐hydroxyethyl decomposition is CH3CHO + H, with C2H3OH + H and CH3 + CH2O, being minor channels. Rate coefficients are strongly dependent on temperature and pressure and are recommended with attendant uncertainty factor estimates. The relative roles of vinyl alcohol and acetaldehyde in the context of combustion chemistry are also discussed.

Kinetics of isopropanol decomposition and reaction with H atoms from shock tube experiments and rate constant optimization using the method of uncertainty minimization using polynomial chaos expansions (MUM‐PCE)

“…Calculations from Dames 34 predict that about 92% of CH 3 C(H)OH will decompose to either acetaldehyde or vinyl alcohol, while 8% will form formaldehyde. Since vinyl alcohol will tautomerize to acetaldehyde, R1499 will overwhelmingly lead to acetaldehyde as the closed shell product.…”

“…6,[30][31][32][33] Fission of the C−O bond has too large a barrier to play a significant role. 30 Scheme 1 shows the main unimolecular reactions of isopropanol: dehydration (R1498) produces propene (C 3 H 6 ) and water; C−C bond fission (R1499) produces a methyl radical (CH 3 ) and a CH 3 CHOH radical, whichaccording to calculations by Dames 34 -will decompose to either acetaldehyde (CH 3 CHO) or formaldehyde (CH 2 O).…”

Theoretical studies on the mechanism and kinetic for CH3CH2O + HO2 and CH3CHOH + HO2 reactions

“…It has been suggested that the further oxidation of CH 3 O and CH 2 OH radicals by HO 2 produces more stable species like formaldehyde, formic acid, or hydrogen peroxide Equations to . Thus, the reactions of CH 3 CH 2 O and CH 3 CHOH with HO 2 are one of the most important degradation processes in the atmosphere …”

“…[26] Thus, the reactions of CH 3 CH 2 O and CH 3 CHOH with HO 2 are one of the most important degradation processes in the atmosphere. [27][28][29][30][31][32][33][34][35][36][37] CH 3 (5) There is no any experimental and theoretical report in the literature about the reactions of CH 3 CH 2 O + HO 2 and CH 3 CHOH + HO 2 . By contrast, a theoretical study on the singlet and triplet reaction mechanisms of CH 3 O + HO 2 and CH 2 OH + HO 2 has been reported at CCSD (T)/aug-cc-pVTZ//MPWB1K/6-31 + G (d,p) level of theory by Mousavipour and co-workers, [38] which provides the meaningful information to the reaction mechanism that involved HO 2 radical.…”

High-pressure pyrolysis and oxidation of ethanol

“…The α-hydroxyethyl radical (CH 3 CHOH) is presumably the major product of Habstraction from ethanol. For the decomposition of CH 3 CHOH (R6), the rate constants are taken from an RRKM study by Dames [41] who predicted the major branch, CH 3 CHOH(+M) = CH 3 CHO+H(+M) (R6a) to be faster by up to one order of magnitude compared to an earlier calculation by Xu et al [46].…”