功能化芳香三乙烯乙烯的热循环二氧化合成和电子因素
Bryan K Spraul1, S Suresh, Jianyong Jin
1Department of Chemistry and Center for Optical Materials Science and Engineering Technologies (COMSET), Clemson University, Clemson, South Carolina, USA.
Journal of the American Chemical Society
|May 25, 2006
概括
新的芳香三乙烯乙烯被合成并循环二化,形成高环 (PFCB) 化合物. 电子吸收组被发现可以降低这种重要的聚合反应的速率.
科学领域:
- 有机化学 有机化学
- 聚合物化学 聚合物化学
背景情况:
- 芳香三乙烯乙烯是多功能构建块.
- perfluorocyclobutyl (PFCB) 连接提供了独特的材料特性.
研究的目的:
- 为了合成新型的p替代芳香三维尼尔乙醇.
- 为了研究它们的热循环二分化到PFCB化合物.
- 探索替代剂对反应动力学的影响.
主要方法:
- 制备 19 p 置换的芳香三维尼尔乙烯化合物.
- 热基介导的循环二极化.
- 使用19F核磁共振光谱和哈梅特方程进行分析.
主要成果:
- 成功合成了二功能的PFCB化合物.
- 证明了三维尼尔乙烯中间体的功能组耐受性.
- 量化替代剂对循环二极化速率的影响,取电子组减缓反应.
- 计算的哈梅特反应常量 (rho = -0.46 在120°C, -0.59 在130°C).
结论:
- 芳香三维尼尔乙烯可以有效地循环二化为PFCB化合物.
- 这种反应适用于制造阶段增长聚合物的单体.
- 这项研究为这个循环二极化过程建立了第一个线性自由能量关系.
相关概念视频
Thermal and Photochemical Electrocyclic Reactions: Overview
Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
Thermal Electrocyclic Reactions: Stereochemistry
The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Photochemical Electrocyclic Reactions: Stereochemistry
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
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Electrophilic addition of halogens to alkenes proceeds via a cyclic halonium ion to form a 1,2-dihalide or a vicinal dihalide.
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