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A PM3 Molecular Orbital Study on the Conformational Equilibrium of Cyclohexane upon α-Cyclodextrin Inclusion Complexation
Huang Xin, Liu Lei, Li Xiaosong, Guo Qingxiang, Liu Youcheng
Department ofChemistry and Open Laboratoryfor Bond-Selective Chemistry, University ofScience and Technology ofChina, Hefei 230026
Abstract:
The effect ofα-cyclodextrin (α-CD) inclusion complexation on the conformational equilibrium of cyclo- hexane wasstudied with thesemiempirical PM3 molecularorbital calculations. The calculation results indicated that the chair form of cyclohexane is 18.5 kJ·mol-1lower than that of boat one in energy, however, theα-cyclodextrin inclusion complex of boat cycl ohexane is 4.4 kJ·mol-1more stable than the complex of chair form. It demon-strated that the conformational equilibrium of cyclohexane was influenced by theα-CD inclusion complexation. Hence, caution should be given when extrapolating the conformational behaviors of the guest compounds in the supramolecular systems totheir free forms, since the interactionsbetween the host and guest significantly affect the conformation of the guest compounds.
Key words:  α-Cyclodextrin, Cyclohexane, Conformational equilibrium, PM3
FundProject:
α-环糊精包合物中环己烷构象平衡的PM3研究
黄欣, 刘磊, 李晓松, 郭庆祥, 刘有成
中国科学技术大学化学系,中国科学院选键化学开放实验室 合肥 230026
摘要:
用PM3分子轨道方法研究了α-环糊精的包合作用对环己烷构象平衡的影响。发现α-环糊精的包合作用可以改变环己烷的构象平衡。计算结果表明,虽然环己烷的椅式构象比船式构象稳定18.5kJ*mol-1,但在α-环糊精的包合物中,船式环己烷包合物比椅式环己烷包合物稳定4.4kJ*mol-1。因此,超分子体系中客体分子的构象平衡不能简单地从其游离态的构象平衡外推得到,而应该考虑在超分子体系中分子间相互作用对构象的影响。
关键词:  α-环糊精  环己烷  构象平衡  PM3
DOI:10.1088/1674-0068/13/5/539-543
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