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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Conformational Composition of Gaseous trans-1,4-Dichlorocyclohexane. Molecular Structures and Energy Differences of the aa and ee Components from Gas-Phase Electron Diffraction and ab Initio Calculations
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Conformational Composition of Gaseous trans-1,4-Dichlorocyclohexane. Molecular Structures and Energy Differences of the aa and ee Components from Gas-Phase Electron Diffraction and ab Initio Calculations

机译：气态反式1，4-二氯环己烷的构象组成。气相电子衍射和从头算计算aa和ee组分的分子结构和能量差异

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Electron-diffraction patterns from gaseous trans-1,4-dichlorocyclohexane at a temperature of 105 deg C have been analyzed with the help of results from ab initio molecular orbital calculations to yield the structures of the ee and aa forms (equatorially and axially disposed chlorine atoms, respectively) of the molecule and the composition of the mixture. The model of this complicated system was defined in terms of the structure of the ee form, tying many of the parameters of the aa form to those of the ee by parameter differences calculated ab initio. Some of the results (r_g/A, angle_e/deg; 2#sigma# uncertainties) for the ee (aa) forms from the preferred model are = 1.115(4) (1.113); r(C_1-C_2) = 1.525(6) (1.525); r(C_2-C_3) = 1.542(13) (1.535); r(C-Cl) = 1.799(3) (1.812); r(Cl...Cl) = 6.309(11) (5.236); angle(C_2C_1C_6) = 109.9(14) (110.1); angle(CCCl) = 109.7(4) (109.8); flap (the angle between the planes C_2C_1C_6 and C_2C_3C_5C_6) = 51.7(19) (47.2(12)). The mole fraction of the ee form was determined to be 0.46(6). The structural predictions of ab initio calculations were tested by optimizations at several levels, among them HF/6-31G~*, MP2/6-311G~*, QCISD/6-311+G(2df,p). MPw1PW91/6-311G~*, B3P86/6-311G~*, and B3P86/6-311+G(2df,p). Parameter values from each of these calculations are in good agreement with experiment, but those from the HF/6-31G~* are poorest. The experimental composition is most accurately predicted by the MP2/6-311G~* and QCISD/6-311+G(2df,p) calculations from the conformational energy differences #DELTA#E_(theor) corrected for zero-point energy and entropy differences. The composition of the system is discussed in relation to that of monochlorocyclohexane.
机译：在从头算分子轨道计算的结果的帮助下，分析了温度为105℃时，气态反式1,4,2-二氯环己烷的电子衍射图，得出了ee和aa形态（赤道和轴向布置的氯）的结构分子）和混合物的组成。根据ee形式的结构定义了此复杂系统的模型，通过从头算出的参数差异将aa形式的许多参数与ee的那些参数联系在一起。首选模型的ee（aa）形式的某些结果（r_g / A，angle_e / deg; 2＃sigma＃不确定性）为 = 1.115（4）（1.113）; r（C_1-C_2）= 1.525（6）（1.525）; r（C_2-C_3）= 1.542（13）（1.535）; r（C-Cl）= 1.799（3）（1.812）; r（Cl ... Cl）= 6.309（11）（5.236）;角度（C_2C_1C_6）= 109.9（14）（110.1）;角（CCCl）＝ 109.7（4）（109.8）;襟翼（平面C_2C_1C_6和C_2C_3C_5C_6之间的夹角）= 51.7（19）（47.2（12））。 ee形式的摩尔分数经测定为0.46（6）。通过从头开始计算的结构预测在多个级别上进行了优化，其中包括HF / 6-31G〜*，MP2 / 6-311G〜*，QCISD / 6-311 + G（2df，p）。 MPw1PW91 / 6-311G〜*，B3P86 / 6-311G〜*和B3P86 / 6-311 + G（2df，p）。这些计算中的每一个参数值都与实验很好地吻合，但是HF / 6-31G〜*的参数值最差。根据对零点能量和熵校正的构象能差＃DEL ## E_（theor），通过MP2 / 6-311G〜*和QCISD / 6-311 + G（2df，p）计算可以最准确地预测实验成分差异。关于一氯环己烷的体系组成进行了讨论。

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