Chirality Induction in Cyclocopolymerization Arising from the Chiral Twist of Templates
摘要:
The cyclopolymerization capable of forming monomeric units without planes of symmetry provides one useful means for asymmetric polymerization. Three succharides: L-threitol, α-D-glucose, and D-mannitol, were used as a template for asymmetric induction in radical cyclocopolymerization. The bis (p-vinylbenzoate) monomers (1a-c) (M 1 ) derived from the templates were copolymerized with styrene (M 2 ). The resulting copolymers (2a-c) were canverted into poly [(methyl 4-vinylbenzoate) -co-styrene] s (3a-c). The polymers were optically active; a sourse of chirality was the isolated M 1 unit. The exciton chirality method was employed for determining the absolute configuration of the cyclic units. The template having R, R-configuration transmitted its chirality to the main chain in the intramolecular cyclization of the monomer to form an enantiomeric S, S-racemo cyclic unit. The template having S, S-configuration gave the R, R-racemo cyclic unit. The acyclic template, (2S, 4S) -2, 4-pentanediol, was more effective than the cyclic templates such as the D-mannitol and L-threitol. The (2S, 4S) -2, 4-pentanediyl template approximately doubled in effect for the asymmetric induction by comparison with the (S) -1, 3-butanediyl one. The difference in the circular dichroism (CD) spectrum between the monomers from these templates was estimated by calculating the most stable rotational conformation and its energy level. The source of the optical activity in the cyclocopolymerizations was estimated by means of molecular mechanics and semiempirical molecular orbital calculation. The copolymerization of bis (methacryloyloxy) monomer (4a) (M 1 ) from L-threitol with styrene (M 2 ) induced the new chirality due to the isolated M 1 unit in the main chain as well. In contrast to the case of the L-threitol template, the copolymerization of bis (methacryloyloxy) monomer (4b) from D-mannitol indicated that the new chirality should be induced by the M 1 diad unit rather than the isolated unit.
展开
关键词:
Asymmetric Polymerization Cyclocopolymerization Chiral Radical Polymerization Divinyl Monomer Vinylbenzoate Methacrylate Tamplate Chiral Diol Exciton Circular Dichroism Spectrum Cyclic Unit Absolute Configuration Racemo Computational Chemistry
DOI:
10.1295/koron.54.684
被引量:
年份:
1997
通过文献互助平台发起求助,成功后即可免费获取论文全文。
相似文献
参考文献
引证文献
来源期刊
引用走势
辅助模式
引用
文献可以批量引用啦~
欢迎点我试用!