乙烯基组在聚乙烯的表面循环,涉及不寻常的五角形到六角形转换
Marco Di Giovannantonio1,2, Zijie Qiu3,4, Carlo A Pignedoli5
1Empa, Swiss Federal Laboratories for Materials Science and Technology, nanotech@surfaces Laboratory, 8600, Dübendorf, Switzerland. marco.digiovannantonio@ism.cnr.it.
Nature communications
|March 1, 2024
概括
这项研究详细介绍了黄金表面上乙烯基组的表面合成反应. 乙烯基组循环形成聚合物,可以转化为聚[k]四烯,使精确的纳米结构制造成为可能.
科学领域:
- 表面化学 表面化学
- 有机合成 有机合成
- 材料科学是一种材料科学.
背景情况:
- 表面合成使得分子架构的精确制造成为可能.
- 聚乙烯前体被用于研究分子内反应.
研究的目的:
- 在Au上详细描述乙烯基基组的反应步骤.
- 通过热激活来研究新型纳米结构的形成.
主要方法:
- 在Au111) 表面上利用超高真空条件.
- 在一个聚乙烯模型系统中研究乙烯基组的分子内反应.
主要成果:
- 乙烯基团循环形成二甲基二二二二重复单元.
- 聚合物通过五角形到六角形的重新排列转化为聚[k]四烯.
- 产品的形成高度依赖于温度.
结论:
- 乙烯基组的表面反应提供了基本的化学见解.
- 温度控制允许精确制造复杂的低维纳米结构.
- 这种方法为纳米结构合成提供了高精度和高产量.
相关概念视频
Thermal and Photochemical Electrocyclic Reactions: Overview
2.3K
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.
2.3K
Olefin 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
Thermal Electrocyclic Reactions: Stereochemistry
2.0K
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.
2.0K
Woodward–Hoffmann Selection Rules and Microscopic Reversibility
3.1K
Electrocyclic reactions, cycloadditions, and sigmatropic rearrangements are concerted pericyclic reactions that proceed via a cyclic transition state. These reactions are stereospecific and regioselective. The stereochemistry of the products depends on the symmetry characteristics of the interacting orbitals and the reaction conditions. Accordingly, pericyclic reactions are classified as either symmetry-allowed or symmetry-forbidden. Woodward and Hoffmann presented the selection criteria for...
3.1K
Photochemical Electrocyclic Reactions: Stereochemistry
1.8K
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
1.8K
Aromatic Hydrocarbon Cations: Structural Overview
2.8K
Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
Removing one hydrogen from the intervening CH2 group...
Removing one hydrogen from the intervening CH2 group...
2.8K


