基组5中意想不到的周期性 乳的环开放聚合的启动者
Antoine Buchard1,2, Matthew G Davidson1,2, Gerrit Gobius du Sart3
1Institute for Sustainability, University of Bath, Bath BA2 7AY, United Kingdom.
Inorganic chemistry
|December 20, 2023
概括
(V) 和 (V) 复合物催化乳的环开聚合 (ROP),就像 ε-caprolactone 一样. 催化剂表现出优越的活性,通过独特的启动机制使新的聚合物和受控的聚合物特性成为可能.
科学领域:
- 有机金属化学 有机金属化学
- 聚合物化学 聚合物化学
- 催化剂是一种催化剂.
背景情况:
- 氨基三 (酸) 支持的 () 和 () 乙氧化物是已知的乳环开放聚合 (ROP) 的启动剂.
- 之前的研究表明, (V) 复合物在ROP中表现出比 (V) 复合物更高的活性.
- 某些乳的ROP,如δ-valerolactone和rac-β-butyrolactone,在V组或介导条件下具有挑战性.
研究的目的:
- 为了研究和比较 ε-caprolactone (ε-CL) 添加剂的催化活性,在乳 ROP中支持,氨基三 () 和 () 乙氧化物.
- 探索这些 (V) 和 (V) 系统的启动机制和反应性趋势.
- 为了证明新型和的合成和催化效用,V) 和-V) δ-瓦洛拉克添加物.
主要方法:
- 基,氨基三 ((phenolate) 支持的 ((V) 和 ((V) 乙氧化与e-caprolactone,δ-valerolactone和rac-β-butyrolactone的合成.
- 使用这些合成的复合物,对各种乳进行催化环开放聚合 (ROP).
- 动力学研究,以确定和比较 (V) 和 (V) 催化剂的活性.
- 通过机械学研究,研究聚合起始机制.
主要成果:
- 与同结构的 (V) 复合体相比, (V) 种在 ε-caprolactone 的 ROP 中表现出更高的催化活性,这与之前的文献相矛盾.
- (V) 和 (V) 系统都成功启动了δ-valerolactone和rac-β-butyrolactone的ROP,其中的同源始终表现出更高的活性.
- 合成了新的阴离子乙烯基-- (V) 和- (V) -瓦洛拉克添加物,证实了-瓦洛拉克作为配体的实用性和该方法的通用性.
- 启动机制被阐明为氧化物对协调的乳的分子内核友性攻击.
结论:
- ((V) 催化剂在乳ROP中表现出比 ((V) 类型相比更高的活性,挑战了现有的文献.
- 开发的催化系统为 ε-caprolactone, δ-valerolactone 和 rac-β-butyrolactone 的 ROP 提供了一条多功能途径,包括以前未实现的聚合物.
- 独特的分子内启动机制允许通过独立操纵启动和动力学来精确控制聚合物结构,特性和分散性.
更多相关视频
相关概念视频
00:57Cationic Chain-Growth Polymerization: Mechanism
2.3K
The cationic polymerization mechanism consists of three steps: initiation, propagation, and termination. In the initiation step of the polymerization process, the π bond of a monomer gets protonated by the Lewis acid catalyst, which is formed from boron trifluoride and water. The protonation of the π bond generates a carbocation stabilized by the electron‐donating group. In the propagation step, the π bond of the second monomer acts as a nucleophile and attacks the...
2.3K
01:04Anionic Chain-Growth Polymerization: Mechanism
2.0K
The mechanism for anionic chain-growth polymerization involves initiation, propagation, and termination steps. In the initiation step, a nucleophilic anion, such as butyl lithium, initiates the polymerization process by attacking the π bond of the vinylic monomer. As a result, a carbanion, stabilized by the electron‐withdrawing group, is generated. The resulting carbanion acts as a Michael donor in the propagation step and attacks the second vinylic monomer, which acts as a Michael...
2.0K
01:20Anionic Chain-Growth Polymerization: Overview
2.1K
The polymerization process that involves carbanion as an intermediate is called anionic polymerization. It is also a type of addition or chain-growth polymerization. Anionic polymerization gets initiated by a strong nucleophile such as an organolithium or a Grignard reagent. The most commonly used initiator for anionic polymerization is butyl lithium. Monomers involved in anionic polymerization must possess a vinyl group bonded to one or two electron-withdrawing groups. For instance,...
2.1K
02:24Acid-Catalyzed Ring-Opening of Epoxides
7.3K
Epoxides that are three-membered ring systems are more reactive than other cyclic and acyclic ethers. The high reactivity of epoxides originates from the strain present in the ring. This ring strain acts as a driving force for epoxides to undergo ring-opening reactions either with halogen acids or weak nucleophiles in the presence of mild acid. The acid catalyst converts the epoxide oxygen, a poor leaving group, into an oxonium ion, a better leaving group, making the reaction feasible. The...
7.3K
02:26Base-Catalyzed Ring-Opening of Epoxides
8.5K
Due to their highly strained structures, epoxides can readily undergo ring-opening reactions through nucleophilic substitution, either in the presence of an acid or a base. The nucleophilic substitution reactions in the presence of acid are called acid-catalyzed ring-opening reactions, and nucleophilic substitution reactions in the presence of a base are called base-catalyzed ring-opening reactions. Epoxides undergo base-catalyzed ring-opening reactions in the presence of a strong nucleophile...
8.5K
01:16Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)
2.6K
Ring-opening metathesis polymerization or ROMP involves strained cycloalkenes as starting materials. The mechanism of ROMP proceeds by reacting cycloalkene with Grubbs catalyst to give metallacyclobutane intermediate which undergoes a ring-opening reaction to form new carbene. The new carbene reacts with another molecule of cycloalkene. Repetition of these steps leads to the formation of an unsaturated open-chain polymer product. All these steps are reversible, however, relieving the ring...
2.6K