NMR Studies and Conformational Energy Calculations of 1,2-Dimethoxyethane and Poly(oxyethylene)
NMR Studies and Conformational Energy Calculations of 1,2-Dimethoxyethane and Poly(oxyethylene)
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1,2-二甲氧基乙烷和聚氧乙烯的核磁共振研究和构象能计算
DOI：
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发表时间：
1985
期刊：
影响因子：
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通讯作者：
A. Abe
中科院分区：
文献类型：
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作者：
K. Tasaki;A. Abe
用核磁共振技术对聚氧乙烯单体模型化合物1，2-二甲氧基乙烷（DME）的构象进行了研究。在转动异构态方案的基础上，分析了邻位耦合常数与温度的关系。对于C-C键，13 CH卫星边带提供所需信息。构象能Eσ，代表相对于反式的偏置态能量，被发现在−0.5至−1.2 kcal mol−1的范围内变化，这取决于溶剂系统。同时测定了邻位1H-1H偶联的JT和JG值：JT=11.4±0.3和JG=2.3±0.1 Hz。对于围绕C-O键的旋转，研究了与末端甲基相关的邻位13 C-1H耦合常数。采用JG=1.3 Hz，则偏态和反式态之间的能量差估计为Eρ=0.8 ~ 1.1 kcal mol−1。在这些处理中，严格考虑了键旋转沿着链的邻位依赖特性。所得聚合物的Eσ和Eρ值与DME相当。结果与以前报道的Viti等。和Mastuzaki等。
Conformational studies on 1,2-dimethoxyethane (DME), a monomer model compound of poly(oxyethylene), have been carried out by using NMR technique. The observed temperature dependence of the vicinal coupling constants was analyzed on the basis of the rotational isomeric state scheme. For the C–C bond, the 13CH satellite side bands provide the desired information. Conformational energy Eσ, representing the energy of the gauche state expressed relative to the trans, was found to vary in a range −0.5 to −1.2 kcal mol−1, depending on the solvent system. Values of JT and JG for the vicinal 1H–1H coupling were determined concomitantly: JT=11.4±0.3 and JG=2.3±0.1 Hz. For the rotation about the C–O bond, the vicinal 13C–1H coupling constant associated with the terminal methyl group was studied. Adoption of JG=1.3 Hz leads to an estimate of Eρ=0.8 to 1.1 kcal mol−1 for the energy difference between the gauche and trans states. In these treatments, the neighbor-dependent character of the bond rotation along the chain was rigorously taken into account. The values of Eσ and Eρ derived for the polymer are comparable with those of DME. The results are compared with those reported previously by Viti et al. and Mastuzaki et al.