首页> 外文期刊>International Journal of Chemical Kinetics >Thermochemical Properties from Ab Initio Calculations:pi-and sigma-Free Radicals of Importance in Soot Formation:·C_3H_3(Propargyl),·C_4H_3,·C_(13)H_9(Phenalenyl),·C_6H_5(Phenyl),~·C10H7(Naphthyl),·C_(14)H_9(Anthryl),·C_(14)H_9(Phenanthryl),·C_(16)H_9(pyrenyl)·C_(12)H_7 (acenaphthyl), and ·C_(12)H_9 (biphenylyl)
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Thermochemical Properties from Ab Initio Calculations:pi-and sigma-Free Radicals of Importance in Soot Formation:·C_3H_3(Propargyl),·C_4H_3,·C_(13)H_9(Phenalenyl),·C_6H_5(Phenyl),~·C10H7(Naphthyl),·C_(14)H_9(Anthryl),·C_(14)H_9(Phenanthryl),·C_(16)H_9(pyrenyl)·C_(12)H_7 (acenaphthyl), and ·C_(12)H_9 (biphenylyl)

机译:从头算计算得出的热化学性质:烟尘形成中重要的pi和σ自由基:·C_3H_3(炔丙基),·C_4H_3,·C_(13)H_9(苯基),·C_6H_5(苯基),〜·C10H7(萘基) ),·C_(14)H_9(蒽基),·C_(14)H_9(菲基),·C_(16)H_9(吡啶基)·C_(12)H_7(ac基)和·C_(12)H_9(联苯基) )

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摘要

The calculated difference in the standard heat of formation DELTA DELTA_fH°(298.15)of n-and i-C4H3 free radicals is 37.9 k)mol~(-1)for G3MP2B3 and 45.0 kJ mol~(-1)for CCSD(T)-CBS(WlU)calculations,which seems to preclude the direct even-carbon radical pathway to benzene and higher PAH(polycyclic aromatic hydrocarbon)formation including soot in a hydrocarbon flame.For the phenyl-type sigma-radicals listed in the title,absolute values of DELTA_fH°(298.15)have been calculated using G3MP2B3-computed values of bond dissociation energies D°(298.15)and combined with experimental values of DELTA_f H°(298.15)for the parent hydrocarbon because of a slight systematic overprediction of the thermodynamic stability of large PAHs by the applied computational G3MP2B3 method.Standard enthalpies of formation DELTA_fH°(298.15)as well as absolute entropies S° and heat capacities C_p~° are given for a series of pi-and sigma-free radicals important to combustion as a function of temperature.A spread of roughly 40 kJ mol~(-1)in the average C-H bond strength of PDELTA H leading to sigma-radicals has been calculated,the lowest leading to 4-phenanthryl(463.6 kJ mol~(-1)),the highest leading to 2-biphenylyl radical(502.5 kJ mol~(-1)).
机译:n和i-C4H3自由基的标准形成热量DELTA DELTA_fH°(298.15)的标准差对于G3MP2B3为37.9 k)mol〜(-1),对于CCSD(T)为45.0 kJ mol〜(-1) -CBS(WlU)计算,这似乎排除了直接的偶数碳自由基途径通向苯和更高的PAH(多环芳烃)形成,包括碳氢化合物火焰中的烟ot。对于标题中所列的苯基型σ自由基,绝对已使用G3MP2B3计算的键解离能D°(298.15)的值计算了DELTA_fH°(298.15)的值,并结合了对母体烃的DELTA_fH°(298.15)的实验值,因为对热力学稳定性的系统性过度预测应用一系列的G3MP2B3计算方法计算了大型PAHs。对于一系列对燃烧重要的pi和sigma-自由基,给出了标准的形成焓DELTA_fH°(298.15)以及绝对熵S°和热容C_p〜°。温度的函数。粗糙的扩散计算出PDELTA H的平均CH键强度导致σ自由基的40 kJ mol〜(-1),最低导致4-菲基(463.6 kJ mol〜(-1)),最高导致2。 -联苯基(502.5 kJ mol〜(-1))。

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