APPLICATIONS OF NMR AND THEORETICAL CALCULATIONS TO STUDY THE O-H∙∙∙N INTRAMOLECULAR HYDROGEN BOND EFFECT ON THE CONFORMATIONAL EQUILIBRIUM OF CIS-3-N-ETHYLAMINOCYCLOHEXANOL AND CIS-3-N,N-DIETHYLAMINOCYCLOHEXANOL

IF 0.5 4区 化学 Q4 CHEMISTRY, MULTIDISCIPLINARY
Paulo R. de Oliveira, R. Rittner, Palimécio Guerrero Jr., P. Batista, G. Costa
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引用次数: 0

Abstract

Textbooks show that in cis-1,3-disubstituted cyclohexane molecule, the conformer with the substituents in the diaxial positions is higher in energy and hence, it presents a low population in the conformational equilibrium. The diaxial conformer is destabilized by the repulsion between the substituent groups and the axial hydrogen atoms on the same side of the ring. This interaction is known as the 1,3-diaxial interaction. In this study, the solvent effect on the conformational equilibria of cis-3-N-ethylaminocyclohexanol (cis-3-EACOL) and cis-3-N,N-diethylaminocyclohexanol (cis-3-DEACOL) has been assessed through the spin-spin coupling constant (3JHH). The results show that the diaxial conformation of cis-3-EACOL decreases from 92% in CCl4 (∆Gee-aa = 1.48 kcal mol-1 ) to 10% in DMSO-d6 (∆Gee-aa = −1.31 kcal mol-1). For cis-3-DEACOL the diaxial conformer decreased from 36% in CCl4 (∆Gee-aa = −0.33 kcal mol-1) to 7% in Pyridine-d5 (∆Gee-aa = −1.55 kcal mol-1). The stabilization of the diaxial conformer in nonpolar solvents takes place due to the O-H···N intramolecular hydrogen bond, which overcomes the 1,3-diaxial steric interactions.
应用核磁共振和理论计算研究o-h∙∙n分子内氢键对顺-3- n -乙基氨基环己醇和顺-3- n, n -二乙基氨基环己醇构象平衡的影响
课本表明,在顺式-1,3-二取代环己烷分子中,取代基在二轴位置的构象能量较高,因此在构象平衡中占比较低。取代基与环同侧的轴向氢原子之间的斥力使二轴形构象不稳定。这种相互作用被称为1,3-二轴相互作用。本研究通过自旋-自旋耦合常数(3JHH)评价了溶剂对顺-3- n-乙基氨基环己醇(顺-3- eacol)和顺-3- n, n-二乙基氨基环己醇(顺-3- deacol)构象平衡的影响。结果表明,顺-3- eacol的双轴构象从CCl4(∆Gee-aa = 1.48 kcal mol-1)中的92%下降到DMSO-d6(∆Gee-aa = - 1.31 kcal mol-1)中的10%。顺-3- deacol的双轴构象从CCl4中的36%(∆Gee-aa = - 0.33 kcal mol-1)下降到吡啶-d5中的7%(∆Gee-aa = - 1.55 kcal mol-1)。在非极性溶剂中,由于O-H···N分子内氢键克服了1,3-二轴位相互作用,使得双轴构象稳定。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Quimica Nova
Quimica Nova 化学-化学综合
CiteScore
1.60
自引率
12.50%
发文量
72
审稿时长
2-4 weeks
期刊介绍: Química Nova publishes in portuguese, spanish and english, original research articles, revisions, technical notes and articles about education in chemistry. All the manuscripts submitted to QN are evaluated by, at least, two reviewers (from Brazil and abroad) of recognized expertise in the field of chemistry involved in the manuscript. The Editorial Council can be eventually asked to review manuscripts. Editors are responsible for the final edition of QN.
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