CONFORMATIONS OF 1,2-DIMETHOXYETHANE IN THE GAS AND LIQUID PHASES FROM MOLECULAR DYNAMICS SIMULATIONS
CONFORMATIONS OF 1,2-DIMETHOXYETHANE IN THE GAS AND LIQUID PHASES FROM MOLECULAR DYNAMICS SIMULATIONS
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分子动力学模拟中 1,2-二甲氧基乙烷在气相和液相中的构象
DOI：
10.1021/ja00106a061
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发表时间：
1995
影响因子：
15
通讯作者：
D. Y. Yoon
中科院分区：
文献类型：
--
作者：
Grant D. Smith;R. Jaffe;D. Y. Yoon
我们最近对1，2-二甲氧基乙烷（DME）构象异构体的几何构型和能量进行了从头计算。1-1 2我们发现ttt构象的能量最低，而tgt和tg±g：¥构象的能量仅高出0.1-0.2 kcal/mol。构象能产生与气相电子衍射研究3一致的构象布居，其预测在273 K下构象布居的顺序为tg±g：f+ tg±g±> tgt> ttt。（例如，参考文献4-6）和模拟（如参考文献7和8）指出二甲醚在液相和固相中的构象与气相不同;即DME中存在着凝聚相效应，改变了分子的构象布居。矩阵隔离studies 6表明，thettt构象是最稳定的构象在氩矩阵在34 K，与我们的研究结果一致，这是最低的能量构象。在液态和结晶态，光谱研究表明，tgt conformer 4是优选的。在气相中分布最多的tg±g：f构象1-3的分布随着从气相到液相的变化而减少。4 5· 9 tgt构象在液体或固体状态下的稳定性很容易根据极性相互作用来理解; tgt构象具有明显的偶极矩，而ttt构象的偶极矩为零。考虑到tg±gT构象异构体的显著偶极矩，从气相到液相的群体减少不容易理解。
We have recently conducted ab initio electronic structure calculations of the geometries and energies of the conformers of 1, 2-dimethoxyethane (DME). 1-1 2 We found that the ttt conformer is the lowest in energy, while the tgt and tg±g:¥ conformers are only 0.1—0.2 kcal/mol higher in energy. The conformer energies yield conformer populations consistent with gas phase electron diffraction studies3 thatpredict the order of conformer populations to be tg±g: f+ tg±g±> tgt> ttt at 273 K.Both experiment (eg, refs 4—6) and simulation (eg, refs 7 and 8) indicate that the conformations of DME are different in the liquid and solid phases compared to thegas phase; ie, there are condensed phase effects in DME which change the confor-mational populations of the molecule. Matrix isolation studies6 indicate that thettt conformer is the most stable conformer in an argon matrix at 34 K, consistent with our findings that this is the lowest energy conformer. In the liquid and crystalline states, spectroscopic studiesindicate that the tgt conformer4 is preferred. The population of the tg±g: f conformer, the most populous conformer in thegas phase, 1-3 is found to decrease on going from the gas to the liquid. 4 5· 9 The stabilization of the tgt conformer in the liquid or solid state is easily understood in terms of polar interactions; the tgt conformer has an appreciable dipole moment while the ttt conformer has a zero dipole moment. Considering the significant dipole moment of the tg±gT conformer, the decrease in population in going from the gas to the liquid phase is not as easily understood.