Cyclopentadienone Oxidation Reaction Kinetics and Thermochemistry for the Alcohols, Hydroperoxides, and Vinylic, Alkoxy, and Alkylperoxy Radicals

Abstract

Cyclopentadienone has one carbonyl and two olefin groups resulting in 4n + 2 π-electrons in a cyclic five-membered ring structure. Thermochemical and kinetic parameters for the initial reactions of cyclopentadienone radicals with O2 and the thermochemical properties for cyclopentadienone-hydroperoxides, alcohols, and alkenyl, alkoxy, and peroxy radicals were determined by use of computational chemistry. The CBS-QB3 composite and B3LYP density functional theory methods were used to determine the enthalpies of formation (ΔfH°298) using the isodesmic reaction schemes with several work reactions for each species. Entropy and heat capacity, S°(T) and Cp°(T) (50 K ≤ T ≤ 5000 K) are determined using geometric parameters, internal rotor potentials, and frequencies from B3LYP/6-31G(d,p) calculations. Standard enthalpies of formation are reported for parent molecules as cyclopentadienone, cyclopentadienone with alcohol, hydroperoxide substituents, and the cyclopentadienone-yl vinylic, alkoxy, and peroxy radicals corresponding to loss of a hydrogen atom from the carbon and oxygen sites. Entropy and heat capacity vs temperature also are reported for the parent molecules and for radicals. The thermochemical analysis shows The R(•) + O2 well depths are deep, on the order of 50 kcal mol(-1), and the R(•) + O2 reactions to RO + O (chain branching products) for cyclopentadienone-2-yl and cyclopentadienone-3-yl have unusually low reaction (ΔHrxn) enthalpies, some 20 or so kcal/mol below the entrance channels. Chemical activation kinetics using quantum RRK analysis for k(E) and master equation for falloff are used to show that significant chain branching as a function of temperature and pressure can occur when these vinylic radicals are formed.

Extensive Theoretical Study of the Thermochemical Properties of Unsaturated Hydrocarbons and Allylic and Super-Allylic Radicals: The Development and Optimization of Group Additivity Values

“…The difference in IDT predictions at 900 K is about an order of magnitude. Using the higher entropy value from the QC calculations, the equilibrium shifts to form this radical which promotes reactivity, resulting in shorter predicted IDTs and Sebbar et al 20 10 hydroxycyclohexadienyl peroxy isomers Chen et al 21 11 C 1 −C 4 hydroperoxides and peroxy radicals Wang et al 22 12 alcohols, hydroperoxides, and vinylic, alkoxy, and alkylperoxy radicals Yommee et al 23 13 hydroxyl-and hydroperoxide-substituted furan, methylfuran, and methoxyfuran Hudzik et al 24 14 isooctane and carbon radicals Snitsiriwat et al 25 better agreement with the experimental data. Further investigation found that, using the GA method, there are two different ways in which the thermochemistry of 2-propenyl-1methyl radical can be calculated, as shown in Figure 4 and Table 2.…”

“…Ritter and Bozzelli developed THERM (THermo Estimation for Radicals and Molecules) based on Benson’s GA method, which can be used as illustrated in Figure . Bozzelli and co-workers − have also studied the thermochemistry of different classes of species including sulfurated, nitridated, fluorinated, oxygenated, and saturated hydrocarbons, Table . Enthalpies of formation, entropies, and heat capacities have been compiled for certain classes of species using density functional theory (DFT) and composite compound methods, from which bond dissociation energies (BDEs) of similar type of bonds and GAVs were systematically reported and compared.…”

Reaction kinetics and thermochemistry of the chemically activated and stabilized primary ethyl radical of methyl ethyl sulfide, CH3SCH2CH2•, with O2 to CH3SCH2CH2OO•

“…where h p is the Planck's constant and к b is Boltzmann's constant, R is gas constant, and R = 1.987 cal mol −1 K −1 . 34,38,49,50 The high-pressure limit rate constant parameters are calculated based on the thermochemical properties of reactant, product, and transition state geometries optimized under the CBS-QB3 level. Temperature-and pressure-dependent rate constants are calculated using the multichannel, multifrequency quantum Rice-Ramsperger-Kassel (QRRK) analysis for k(E) based on a master equation analysis for falloff and stabilization as implemented in the CHEMASTER code.…”

“…The entropy differences between the reactants and the transition states (Δ S ≠ ) over the temperature range of 200–3000 K were used to determine the preexponential factor ( A , s −1 or cm 3 mol −1 s −1 ). The preexponential values of A are expressed by where h p is the Planck's constant and к b is Boltzmann's constant, R is gas constant, and R = 1.987 cal mol −1 K −1 …”

Nonmonotonic Temperature Dependence of the Pressure-Dependent Reaction Rate Constant and Kinetic Isotope Effect of Hydrogen Radical Reaction with Benzene Calculated by Variational Transition-State Theory

“…In addition, it can be burdensome to consistently include the multidimensional tunneling effect and/or anharmonicity effects on rate constants in conventional RRKM calculations. A simpler method is the quantum Rice-Ramsperger-Kassel (QRRK) approximation combined with chemical activation theory, as developed in modern form by Dean and improved further by Dean and Bozzelli and their co-workers, which uses kinetic parameters estimated empirically or obtained from the high-pressure results of canonical-ensemble transition-state theory calculations combined with electronic structure calculations to predict the pressure effect on the dissociation rate. These workers usually used CBS-QB3 theory for the electronic structure calculations.…”