A thermochemistry and kinetic study on the thermal decomposition of ethoxyquinoline and ethoxyisoquinoline

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Quantum chemical calculations were used to study the production of ethylene and keto/enol tautomers from ethoxyquinoline (2‐EQ) and ethoxyisoquinoline (1‐EisoQ and 3‐EisoQ) in the gas phase and ethanol at the MP2/6‐311++G(2d,2p)//BMK/6‐31+G(d,p) level. The obtained data indicate that the elimination of ethylene from 1‐EisoQ and 2‐EQ is slightly more favorable than from 3‐EisoQ. Formation of quinolone and isoquinolone (2‐EQO, 1‐EisoQO, and 3‐EisoQO) is kinetically favored compared to their enols. Decomposition of 2‐EQ and 1‐EisoQ to ethylene and keto forms is thermodynamically and kinetically preferable more stable than the corresponding enols. However, the hydroxy form of 3‐EisoQ is more stable than its keto tautomer in the gas phase and ethanol. The enol tautomers cost less energy when formed from their keto forms rather than from the parent ethoxyquinolone and ethoxyisoquinoline

Atmospheric Oxidation of Methyl Propanoate by the OH radical

The file attached to this record is the author's final peer reviewed version.Atmospheric oxidation of methyl propanoate (MP) by the OH radical has been performed using density functional theory (BMK, BBIK) and ab initio (MP2, CBS-QB3) calculations. The thermodynamic and kinetic parameters are calculated. Three channels have been discussed. These reactions occur through low energy barriers of 3.2–4.3 kcal/mol. The energy barriers increase in the order α < μ < β at CBS–QB3. However, BMK shows slightly different order. Rate constants and branching ratios reveal that the H-abstraction from Cα is as the dominant reaction over the whole temperature range of 200–300 K, with a competition from Cβ channel at lower temperature. The BB1K data reproduce the available experimental rate constant

First-principle studies on the gas phase OH-initiated oxidation of O-toluidine

In the present work, the gas phase reaction of OH radical initiated O-toluidine (OTOD) oxidation is investigated at ROCBS-QB3. Different pathways for OH radical additions to the benzene ring sites and H-atom abstractions are explored in details. At 200 K, the oxidation mechanism of OTOD is thoroughly dominated by the OH-addition to the aromatic ring, whereas the main favorable route is the OH addition to C2 atom with a branching ratio of 52.76%. Raising temperature to 1000 K, the total abstraction of amine's hydrogens becomes the main oxidation pathway for OTOD with contributions of 29.29%. The atmospheric lifetimes of aniline and OTOD are calculated to be 20.74 and 11.23 min., respectively. The fate of OTOD-OH2 (P2) adduct with atmospheric O2 molecule is inspected using the unimolecular Rice-Ramsperger-Kassel-Marcus (RRKM-ME) to verify our results at transition state theory (TST) and shows pressure and temperature dependence of the secondary oxidation mechanism. - 2019 Elsevier B.V.Scopu