使用奇拉催化剂进行乳化物聚合的立体化学:使用聚合物交换机制进行立体控制的新机会
Tina M Ovitt1, Geoffrey W Coates
1Baker Laboratory, Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-1301, USA.
Journal of the American Chemical Society
|February 14, 2002
概括
合金复合物能够在乳酸聚合过程中精确控制多 (乳酸) 立体化学. 这项研究详细介绍了这些催化剂的合成和应用,以创建具有高保真性的立体块PLA.
科学领域:
- 协调化学 协调化学
- 聚合物化学 聚合物化学
- 催化剂是一种催化剂.
背景情况:
- 石化金属氧化物是不对称合成中的有价值的催化剂.
- 乳酸聚合是生物降解的聚乳酸 (PLA) 的关键途径.
- 乳化物的立体控制聚合是定制PLA特性至关重要的.
研究的目的:
- 为了合成和氧化复合物.
- 为了研究它们在控制乳酸脂聚合立体化学中的有效性.
- 为了阐明立体块PLA形成的机制.
主要方法:
- (SalBinap) MOR复合物的合成 (M = Al, Y).
- 使用奇拉催化剂聚合中乳酸和肉乳酸.
- 由此产生的多样乳酸微结构的分析 (立体化学).
主要成果:
- 化复合物4在乳酸聚合过程中表现出极好的立体控制.
- 综合性PLA是从meso-lactide中制造的,使用纯4的等离子分子.
- 立体块PLA (异态和异态) 是使用racemic4形成的.
- 复合体5显示没有立体控制.
结论:
- 化氧化物是立体选择性乳聚合物的有效催化剂.
- 聚合物交换机制解释了立体块PLA的形成.
- 该研究提供了对先进的PLA材料催化剂设计的见解.
相关概念视频
Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
The rate of acid-catalyzed hydration of alkenes depends on the alkene's structure, as the presence of alkyl substituents at the double bond can significantly influence the rate.
Diels–Alder Reaction Forming Cyclic Products: Stereochemistry
The Diels–Alder reaction is one of the robust methods for synthesizing unsaturated six-membered rings. The reaction involves a concerted cyclic movement of six π electrons: four π electrons from the diene and two π electrons from the dienophile.
Radical Halogenation: Stereochemistry
Stereochemistry is the study of the different spatial arrangements of atoms in a given molecule. The stereochemistry of radical halogenations can be understood from three different situations:
Halogenation to form a new chiral center:
Halogenation to form a new chiral center:
Polymer Classification: Stereospecificity
Polymerization generates chiral centers along the entire backbone of a polymer chain. Accordingly, the stereochemistry of the substituent group has a significant effect on polymer properties. Polymers formed from monosubstituted alkene monomers feature chiral carbons at every alternate position in the polymer backbone. Relative to the predominant orientation of substituents at the adjacent chiral carbons, the polymer can exist in three different configurations: isotactic, syndiotactic, and...
Stereochemical Effects of Enolization
The chiral α-carbon of the carbonyl compound is the stereocenter of the molecule. As shown in the figure below, when such a carbonyl compound undergoes racemization under an acidic or basic condition, an achiral enol is formed.
Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry
Diels–Alder reactions between cyclic dienes locked in an s-cis configuration and dienophiles yield bridged bicyclic products.


