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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Kinetics of alpha-hydroxy-alkylperoxyl radicals in oxidation processes. HO2 center dot-initiated oxidation of ketones/aldehydes near the tropopause
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Kinetics of alpha-hydroxy-alkylperoxyl radicals in oxidation processes. HO2 center dot-initiated oxidation of ketones/aldehydes near the tropopause

机译：氧化过程中α-羟基-烷基过氧自由基的动力学。在对流层顶附近，HO2中心点引发的酮/醛氧化

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A comparative theoretical study is presented on the formation and decomposition of α-hydroxy-alkylperoxyl radicals, Q(OH)OO. (Q = RR'C:), important intermediates in the oxidation of several classes of oxygenated organic compounds in atmospheric chemistry, combustion, and liquid-phase autoxidation of hydrocarbons. Detailed potential energy surfaces (PESs) were computed for the HOCH2O2. &REVARR; HO2. + CH2O reaction and its analogues for the alkyl-substituted RCH(OH)OO. and R2C(OH)OO. and the cyclic cyclo-C6H10(OH)OO. The state-of-the-art ab initio methods G3 and CBS-QB3 and a nearly converged G2M//B3LYP-DFT variant were found to give quasi-identical results. On the basis of the G2M//B3LYP-DFT PES, the kinetics of the ≈ 15 kcal/mol endothermal a-hydroxy-alkylperoxyl decompositions and of the reverse HO2. + ketone/aldehyde reactions were evaluated using multiconformer transition state theory. The excellent agreement with the available experimental (kinetic) data validates our methodologies. Contrary to current views, HO2. is found to react as fast with ketones as with aldehydes. The high forward and reverse rates are shown to lead to a fast Q(OH)OO. &REVARR; HO2. + carbonyl quasi-equilibrium. The sizable [Q(OH)OO.]/[carbonyl] ratios predicted for formaldehyde, acetone, and cyclo-hexanone at the low temperatures (below 220 K) of the earth's tropopause are shown to result in efficient removal of these carbonyls through fast subsequent Q(OH)OO. reactions with NO and HO2.. IMAGES model calculations indicate that at the tropical tropopause the HO2.-initiated oxidation of formaldehyde and acetone may account for 30% of the total removal of these major atmospheric carbonyls, thereby also substantially affecting the hydroxyl and hydroperoxyl radical budgets and contributing to the production of formic and acetic acids in the upper troposphere and lower stratosphere. On the other hand, an RRKM-master equation analysis shows that hot α-hydroxy-alkylperoxyls formed by the addition Of 02 to C-1-, C-2-, and C-3-α-hydroxy-alkyl radicals will quasi-uniquely fragment to HO2. plus the carbonyl under all atmospheric conditions.
机译：对α-羟基-烷基过氧自由基Q（OH）OO的形成和分解进行了比较理论研究。 （Q = RR'C :)，这是大气化学，烃类燃烧和液相自氧化过程中几种含氧有机化合物氧化的重要中间体。计算出HOCH2O2的详细势能面（PESs）。 ＆REVARR; HO2。 + CH2O反应及其类似物，用于烷基取代的RCH（OH）OO。和R 2 C（OH）OO。和环状的环-C6H10（OH）OO。发现了最先进的从头开始方法G3和CBS-QB3，以及接近收敛的G2M // B3LYP-DFT变体，可提供近似相同的结果。在G2M // B3LYP-DFT PES的基础上，＆AP的动力学; 15 kcal / mol内热α-羟基-烷基过氧分解和反向HO2分解。使用多构体过渡态理论评估+酮/醛反应。与可用的实验（动力学）数据的极好的一致性验证了我们的方法论。与当前观点相反，HO2。被发现与酮的反应速度与与醛的反应速度一样快。高正向和反向速率显示出可导致快速Q（OH）OO。 ＆REVARR; HO2。 +羰基准平衡。在对流层顶的低温下（220 K以下），预测甲醛，丙酮和环己酮的相当大的[Q（OH）OO。] / [羰基]比显示可快速有效地除去这些羰基随后的Q（OH）OO。 IMAGES模型计算表明，在热带对流层顶，HO2引发的甲醛和丙酮氧化可能占这些主要大气羰基总去除量的30％，从而也大大影响了羟基和氢过氧自由基预算并有助于对流层上部和平流层下部的甲酸和乙酸的生产。另一方面，RRKM主方程分析表明，通过在C-1-，C-2-和C-3-α-羟基烷基中添加02形成的热α-羟基烷基过氧基将准- HO2的唯一片段。在所有大气条件下加羰基。

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