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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Quantum chemical study of low temperature oxidation mechanism of dibenzofuran
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Quantum chemical study of low temperature oxidation mechanism of dibenzofuran

机译：二苯并呋喃的低温氧化机理的量子化学研究

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A density functional theory (DFT) study of the reaction of dibenzofuranyl radical with oxygen molecule has been made. The geometries, energies, and vibrational frequencies of the reactant, transition states, intermediates, and products have been calculated at the B3LYP/6-311+G(3df, 2p)//B3LYP/6-31G(d) level of theory. The initial reaction of dibenzofuran (DBF) with molecular oxygen results in the formation of the 1-dibenzofuranylperoxy radical. The stability of this adduct toward decomposition at low to intermediate temperatures results in it undergoing several possible rearrangements. The lowest energy pathway with a barrier of 24.2 kcal/mol involves a rearrangement to the 1,1-dioxadibenzofuran radical. The next lowest energy pathway involves fission of the O-O linkage whose reaction energy was found to be 37.6 kcal/mol. Transition state theory (TST) calculations indicate that the lowest energy pathway should predominate at temperatures up to about 1200 K. Two other unimolecular reaction pathways with barriers of 45.5 and 91.1 kcal/mol have also been discovered. The latter pathway leads to the formation of a para-quinone (dibenzofuran quinone) which has been detected experimentally in the low-temperature oxidation of DBF [Marquaire, P. M.; Worner, R.; Rambaud, P.; Baronnet, F. Organohalogen Compd. 1999, 40, 519]. Our quantum calculations, however, do not support this latter pathway to quinone formation. Instead, the quinone is most probably formed as a consequence of recombination of the 1-dibenzofuranyloxy radical (produced by peroxy fission) with an O atom in the para position. Each of the unimolecular reaction pathways have been subjected to detailed quantum chemical investigation and transition states and intermediates leading to the final products (principally CO, CO2, and C2H2 with traces of benzofuran and benzene) have been identified. For certain stable intermediates, their possible reactions with molecular oxygen have been further investigated quantum chemically. The present work therefore presents a detailed quantum chemical investigation of the reaction pathways in the low-temperature oxidation mechanism of DBF. Since the dibenzofuran moiety is present in the polychlorinated DBFs, our conclusions should be generally applicable to this family of compounds.
机译：进行了二苯并呋喃基自由基与氧分子反应的密度泛函理论研究。反应物的几何形状，能量和振动频率，过渡态，中间体和产物的计算理论级为B3LYP / 6-311 + G（3df，2p）// B3LYP / 6-31G（d）。二苯并呋喃（DBF）与分子氧的初始反应导致1-二苯并呋喃基过氧自由基的形成。该加合物在低温至中温下分解的稳定性导致其经历了几种可能的重排。势垒为24.2 kcal / mol的最低能量途径涉及到1,1-二恶二苯并呋喃基团的重排。下一个最低的能量途径涉及O-O键的裂变，其反应能量为37.6 kcal / mol。过渡态理论（TST）计算表明，最低能量途径应在最高约1200 K的温度下占主导地位。还发现了另外两个具有45.5和91.1 kcal / mol的势垒的单分子反应途径。后一种途径导致对苯醌（二苯并呋喃醌）的形成，该对苯醌已在DBF的低温氧化中通过实验检测到[Marquaire，P.M。; P.M.，M.M.，1987]。沃纳河; Rambaud，P .; Baronnet，F。有机卤素化合物。 1999，40，519]。但是，我们的量子计算不支持后者形成醌的途径。相反，醌很可能是由于1-二苯并呋喃基氧基（由过氧裂变产生）与对位的O原子重组而形成的。每个单分子反应路径都经过了详细的量子化学研究，并确定了导致最终产物（主要是CO，CO2和C2H2以及痕量苯并呋喃和苯）的过渡态和中间体。对于某些稳定的中间体，其与分子氧的可能反应已通过量子化学进一步研究。因此，本工作提出了DBF低温氧化机理中反应途径的详细量子化学研究。由于二苯并呋喃部分存在于多氯DBF中，因此我们的结论通常应适用于该族化合物。

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