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相关概念视频

Preparation of Epoxides03:00

Preparation of Epoxides

Overview
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...
Olefin Metathesis Polymerization: Overview01:13

Olefin Metathesis Polymerization: Overview

Recently, the development of olefin metathesis polymerization advanced the field of polymer synthesis. Simply put, the reorganization of substituents on their double bonds between two olefins in the presence of a catalyst is known as the olefin metathesis reaction. The use of metathesis reaction for polymer synthesis is called olefin metathesis polymerization.
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists of a...
Polymer Classification: Stereospecificity01:26

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...
Structure and Nomenclature of Ethers02:28

Structure and Nomenclature of Ethers

Structure and Bonding
Ethers are organic compounds with an ether functional group which is characterized by an oxygen atom connected to two — identical or different — alkyl, aryl, or vinyl groups. The C–O–C linkage in dimethyl ether — the simplest ether — has an approximately tetrahedral bond angle of 110.3 degrees. The oxygen atom is sp3- hybridized, with the C–O distance being about 140 pm.
Classification of Ethers
Based on their attached substituent groups, ethers can be classified into two...
Structure and Nomenclature of Alcohols and Phenols02:23

Structure and Nomenclature of Alcohols and Phenols

Overview
Alcohols are one of the most important functional groups in organic chemistry. The name of alcohol comes from the hydrocarbon from which it is derived. Alcohols are organic molecules containing the functional hydroxyl or –OH group directly bonded to carbon. Phenols have an OH group directly attached to a benzene ring. While alcohols are colorless, phenol is a white crystalline compound with a characteristic "hospital smell" odor.
As with other organic compounds, alcohols and phenols...
ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH301:11

ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH3

All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...

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Depolymerizable Olefinic Polymers Based on Fused-Ring Cyclooctene Monomers
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立体特异性八面体组4 bis (酸) 乙醇复合物用于烯聚合.

Elizabeth T Kiesewetter1, Sören Randoll, Madalyn Radlauer

  • 1Department of Chemistry, Stanford University, Stanford, California 94305-5080, USA.

Journal of the American Chemical Society
|April 3, 2010
PubMed
概括

哈夫尼和二酸乙烯复合物是高度活性的α-olefin聚合催化剂. 催化剂表现出优越的立体选择性,产生具有特定结构特征的高质量聚烯.

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:

  • 八面体组4双酸乙烯复合物是已知的α-olefin聚合的催化剂.
  • 甲基氨酸 (MAO) 是这些类型的催化剂的常见激活剂.

研究的目的:

  • 为了研究4组双酸乙醇复合物的催化活性和立体特异性.
  • 为了比较基于 (Hf) 和 (Zr) 的催化剂的性能.
  • 了解连接体结构对催化剂立体选择性的影响.

主要方法:

  • 八面体组4双酸乙烯复合物的合成和表征.
  • 与甲基氨酸 (MAO) 复合物的激活.
  • 进行X射线晶体分析以确定结构上的相似性和差异.
  • 对α-olefin聚合物的研究,以评估催化剂活性和立体特异性.

主要成果:

  • 当MAO激活Zr和Hf复合体时,它们在α-olefin聚合中表现出高活性和立体特异性.
  • X射线晶体学显示Zr和Hf复合体是同结构的,Hf复合体的键长略短.
  • 与Zr复合物相比,Hf复合物产生了更多的立体选择性催化剂,尽管结构相似.

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Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

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  • 三丁替代Hf和Zr复合物产生了高分子量聚烯 (>97%同性,点高达165°C).
  • 结论:

    • 由MAO激活的4组双酸乙复合物是α-olefin聚合物的有效和立体特异性催化剂.
    • 基于哈夫的催化剂比基于的催化剂具有增强的立体选择性.
    • 干结构在决定这些聚合催化剂的立体特异性方面发挥着重要作用.