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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Conformational Characteristics of Methyl Nitrite: A Cryospectroscopic Study
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Conformational Characteristics of Methyl Nitrite: A Cryospectroscopic Study

机译：亚硝酸甲酯的构象特征：低温光谱研究

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摘要

Mid-infrared spectra of solutions in liquid argon, krypton, and xenon of methyl nitrite, which occurs as a mixture of cis and trans conformers, have been investigated. In liquid argon and in liquid krypton at temperatures below 150 K, the rate of conformational equilibration is found to be negligible, while at temperatures above 160 K in liquid krypton, and in liquid xenon, the equilibration is near-instantaneous. The standard enthalpy difference #DELTA#H deg between the conformers in liquid krypton was measured in the 165-205 K interval to be 3.02(9) kJ mol~(-1), with the cis as the more stable conformer. Starting from solutions containing nonequilibrium populations of the conformers, the conformational equilibration was studied as a function of time at five different temperatures between 150 and 160 K in liquid krypton. From these kinetic data, the extinction coefficient ratios for the v_3 and v_8 conformational doublets have been determined to be 1.2(2) and 4.8(8), respectively. The extinction coefficient ratio for c_8 was combined with the value for #DELTA#H deg to yield the value of 5.1(2) J K~(-1) mol~(-1) for the standard conformational entropy difference #DELTA#S deg. The kinetic data have also been used to calculate the enthalpy and entropy of activation for the interconversion from trans to cis conformer, and were found to be 44.0(14) kJ mol~(-1) and 16(9) J K~(-1) mol~(-1), respectively. The results are discussed in light of literaturae data and in light of perturbation Monte Carlo calclations on solvation enthalpy and entropy.
机译：研究了在亚硝酸甲酯的液态氩，k和氙中以顺式和反式构象异构体的混合物形式存在的溶液的中红外光谱。在低于150 K的温度下的液态氩和液态k中，构象平衡的速率可忽略不计，而在高于160 K的温度下，液态liquid和液态氙中的构象平衡速率几乎是瞬时的。在165-205 K的间隔内测得液态k构象异构体之间的标准焓差＃DELTA＃H deg为3.02（9）kJ mol〜（-1），顺式为更稳定的构象异构体。从包含构象异构体非平衡群体的溶液开始，研究了液态rypto中五个不同温度（介于150和160 K之间）随时间变化的构象平衡。从这些动力学数据，确定v_3和v_8构象双峰的消光系数之比分别为1.2（2）和4.8（8）。将c_8的消光系数比率与＃DELTA＃H deg的值相结合，得出标准构象熵差＃DELTA＃S deg的值为5.1（2）J K〜（-1）mol〜（-1）。动力学数据也已用于计算从反式构象到顺式构象异构体相互转化的活化焓和熵，发现为44.0（14）kJ mol〜（-1）和16（9）JK〜（-1 ）mol〜（-1）。根据文献数据和扰动的溶剂化焓和熵的蒙特卡洛计算对结果进行了讨论。

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