Stereoregular Oligomers of Methyl Methacrylate: X-Ray Crystal Structure Analysis and 1H NMR Spectrum of the Trimer
Stereoregular Oligomers of Methyl Methacrylate: X-Ray Crystal Structure Analysis and 1H NMR Spectrum of the Trimer
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甲基丙烯酸甲酯的立构低聚物：三聚体的 X 射线晶体结构分析和 1H NMR 谱
DOI：
10.1295/polymj.21.231
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发表时间：
1989
期刊：
影响因子：
2.8
通讯作者：
K. Hatada
中科院分区：
文献类型：
--
作者：
K. Ute;T. Nishimura;Y. Matsuura;K. Hatada
用高效液相色谱法从甲苯中与t-BuMgBr反应制备的齐聚物中分离出甲基丙烯酸甲酯的三聚体，并通过单晶X射线衍射分析确定了其晶体和分子结构。从庚烷中生长的三聚体的单斜晶体属于空间群P21/n，晶胞常数a=10.047，B=24.743，c=9.026 °，β=109.02°。最终R值为0.050。三聚体的构型为meso-meso构型。在我们以前的报告[K. Hatada等人，Polym. J.，19，1325（1987）]。晶体中沿主链骨架序列t-Bu-CCCCCC-Hω的构象为ttg+tg+（作为（R，S，R）-异构体）沿着。然而，考虑到亚甲基质子的化学位移、1HCOSY谱中观察到的4J相关峰以及ω-末端单元中次甲基和亚甲基质子之间的3 J邻位耦合常数，发现更扩展的状态ttttg+在溶液中占主导地位。ω-末端单元中不等价的亚甲基质子之间的化学位移对于外消旋序列比对于内消旋序列大，而对于链内单体单元则相反。
A trimer of methyl methacrylate was isolated by HPLC from the oligomer mixture prepared in toluene with t-BuMgBr, and the crystal and molecular structure was determined by single crystal X-ray analysis. A monoclinic crystal of the trimer grown from heptane belonged to the space group P21/n having cell constants a=10.047, b=24.743, c=9.026 Å and β=109.02°. The final R value was 0.050. The configuration of the trimer was proved to be meso-meso. This trimer had been differently assigned to meso-racemo isomer in our previous report [K. Hatada et al., Polym. J., 19, 1325 (1987)]. The conformation in the crystal is ttg+tg+ (as (R,S,R)-isomer) along the main chain skeletal sequence t-Bu-CCCCCC-Hω. However, the more extended state ttttg+ was found to be predominant in solution, from the considerations of the chemical shifts of the methylene protons, 4J-correlation peaks observed in 1H COSY spectrum, and 3J vicinal coupling constants between the methine and methylene protons in the ω-end unit. The chemical shift between the nonequivalent methylene protons in the ω-end unit is larger for racemo-sequence than for meso-sequence, while the opposite is true for in-chain monomeric units.
影响因子：
3.2
作者：
T. Kitayama;T. Shinozaki;Eiji Masuda;Masanori Yamamoto;K. Hatada
通讯作者：
T. Kitayama;T. Shinozaki;Eiji Masuda;Masanori Yamamoto;K. Hatada