【摘要】 运用密度泛函方法和Gaussian 3理论,对Coll等人提出的Titan大气中可能生成环氧乙烷的5个反应进行了热化学计算和分析.结果表明:1.所有反应的反应焓变和吉布斯自由能变都小于零,反应都是放热反应,具有较大的自发反应趋势;2.在低温下反应的平衡常数很大,其数据显示反应在低温下正向进行的自发反应趋势更大.可以认为,在Titan大气的低温环境中自然合成环氧乙烷是很有可能的;3.由密度泛函方法和Gaussian 3理论两种方法的计算结果相吻合,互相印证了结论的可靠性.更多还原

【Abstract】 The thermodynamical properties of reactions: H₂CCH₂ + O(¹D)→C₂H₄O, H₂CCH₂ + O(³P)→C₂H₄O, CH₃⁺+C₂H₅OH→C₂H₅O⁺ +CH₄, C₂H₅O⁺ + e^- →C₂H₄O+H and C₂H₅ + O→C₂H₄O +H have been caculated and discussed by means of density Functional theory（DFT） at the B3LYP/6-31G* and G3 level. Those reactions could produce oxirane in Titan’s atmosphere. The geometries of the reactants and products of reactions have been optimized, the energies of the reaction and the equilibrium constant K of reaction have been computed. The analysis of the results shows that: （a） The free Energies of reactions are negative values. It means that reactions could product oxirane spontaneously in titan’s environment. （b） The results of DFT method are in agreement with the date of G3 theory. （c） The converted temperature of reaction（1）, （2） and （5） is respectively 4808.5 Kelvin, 2850.7 Kelvin and 4613.2Kelvin. the authors considered that all of these reactions might be pathways for the synthesis of oxirane in Titan’s atmosphere.更多还原