乳化物与和β-二胺酸复合物的聚合:立体控制和机制
B M Chamberlain1, M Cheng, D R Moore
1Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA.
Journal of the American Chemical Society
|July 18, 2001
概括
新的和催化剂基于β-二胺联体有效聚合乳酸到高立体选择性聚乳酸. 复合物[{BDI-1}ZnO{i}Pr}{2}表现出优异的战术性控制,而类型显示出快速的聚合率.
科学领域:
- 有机金属化学 有机金属化学
- 聚合物科学 聚合物科学
- 催化剂是一种催化剂.
背景情况:
- 聚乳酸 (PLA) 是一种具有越来越多应用的可生物降解聚合物.
- 开发高效和立体选择性催化剂用于PLA合成至关重要.
- β-二胺联体为金属复杂设计提供可调节的框架.
研究的目的:
- 合成和表征 (II) 和 (II) 氧化复合物与β-二氧化联体.
- 评估这些复合物的催化活性和立体选择性在乳化物聚合过程中.
- 研究连接物替代剂和反应条件对聚合结果的影响.
主要方法:
- (II) 和 (II) 氧化物复合物的合成,具有β-二胺联体框架.
- 使用合成的金属复合体,对rac-, meso-和 (S,S) - 乳化物进行环开聚合.
- 对聚合物的战术性,分子量和多分散性的分析.
- 动力学研究以确定对单体和催化剂的反应顺序.
主要成果:
- 复合物[{BDI-1}ZnO{i}Pr}{2}) 在聚合rac-和meso-lactide分别以异质性PLA和联合性PLA的过程中表现出高活性和立体选择性.
- 观察到活体聚合特征,由狭窄的多分散度和线性分子量增长表明.
- 复合物[BDI-1]MgO[i]Pr[2]显示了rac-lactide异常快的聚合率.
- 干替代剂显著影响了聚合率和立体选择性.
结论:
- 支持β-二胺酸的和氧化物是立体选择性聚乳酸合成的有效催化剂.
- 复合物对PLA的战术性提供了很好的控制,而复合物则提供了高的催化速度.
- 这项工作突出了定制的金属二胺酸复合物的潜力,用于循环的受控聚合.
相关概念视频
04:01Factors Affecting Solubility
Compared with pure water, the solubility of an ionic compound is less in aqueous solutions containing a common ion (one also produced by dissolution of the ionic compound). This is an example of a phenomenon known as the common ion effect, which is a consequence of the law of mass action that may be explained using Le Chȃtelier’s principle. Consider the dissolution of silver iodide:
01:08Esters to β-Ketoesters: Claisen Condensation Mechanism
Regular Claisen condensation involves the synthesis of β-ketoesters by combining identical ester molecules bearing two α hydrogens in the presence of an alkoxide base. The reaction commences with the deprotonation of the acidic α hydrogen by the base to form a resonance stabilized ester enolate. This nucleophilic ion then attacks the carbonyl center of another ester molecule to generate a tetrahedral alkoxide intermediate. Next, the expulsion of the alkoxide group from the intermediate restores...
01:14Alkylation of β-Diester Enolates: Malonic Ester Synthesis
Malonic ester synthesis is a method to obtain α substituted carboxylic acids from ꞵ-diesters such as diethyl malonate and alkyl halides.
01:26EDTA: Auxiliary Complexing Reagents
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01:19Masking and Demasking Agents
EDTA titrations may necessitate masking and demasking agents to temporarily protect a particular metal ion in a mixture from the EDTA reaction. These agents facilitate the sequential analysis of the metal ions by forming stable complexes with some—but not all—metal ions during certain steps.
There are many masking agents, such as cyanide, fluoride, triethanolamine, thiourea, and 2,3-bis(sulfanyl)propan-1-ol (formerly 2,3-dimercapto-1-propanol), with the masking agent chosen based on the metal...
There are many masking agents, such as cyanide, fluoride, triethanolamine, thiourea, and 2,3-bis(sulfanyl)propan-1-ol (formerly 2,3-dimercapto-1-propanol), with the masking agent chosen based on the metal...
01:09Complexation Equilibria: Factors Influencing Stability of Complexes
In complexation reactions, metal cations are the electron pair acceptors, and the ligands are the electron pair donors. The stability of the metal complexes depends primarily on the complexing ability of the central metal ion and the nature of the ligands. Generally, the complexing ability of the metal ion depends on the size and charge of the ion. As the metal ion size increases, the stability of the metal complexes decreases, provided that the valency of the metal ion and the ligands remain...