图像制造阻碍了Alkoxy物种在TiO上的旋转
Zhenrong Zhang1, Roger Rousseau, Jinlong Gong
1Fundamental and Computation Sciences Directorate and Institute for Interfacial Catalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, USA.
Journal of the American Chemical Society
|November 26, 2009
概括
这项研究揭示了使用扫描道显微镜和计算方法在二氧化表面上的八氧化分子的旋转动力学. 链旋转受到表面相互作用和附近的基基团的阻碍.
科学领域:
- 表面科学是一门学科.
- 物理化学 物理化学
- 材料科学 材料科学 材料科学
背景情况:
- 了解氧化物表面的分子行为对于催化和电子学至关重要.
- 在表面吸附的有机物种表现出由基质相互作用影响的复杂动态.
研究的目的:
- 为了研究基TiO的八氧基物种的旋转动力学和 conformational 障碍{2}{110}).
- 阐明范德瓦尔斯力和基团在控制这些动态中的作用.
主要方法:
- 使用可变温度扫描道显微镜 (STM) 可视化分子配置.
- 进行分散校正密度函数理论 (DFT-D) 计算,以建模潜在能量表面和旋转障碍.
主要成果:
- STM揭示了多个配置之间旋转的八氧基物种的时间平均快照.
- 由于C...Ti和C...O(b) 相互作用,DFT-D计算发现了显著的旋转障碍 (50-70 kJ mol(-1)) .
- 发现双质基团扰乱了构造群体,并通过C...基排斥增加了旋转障碍.
结论:
- 在TiO{2}{110}上,octoxy的旋转动力学受到基质相互作用和邻近基团的存在的显著影响.
- 这项工作为有机吸附剂在氧化物表面的行为提供了基本的见解.
相关概念视频
02:47Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
Introduction
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
02:44Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide
Alkenes are converted to 1,2-diols or glycols through a process called dihydroxylation. It involves the addition of two hydroxyl groups across the double bond with two different stereochemical approaches, namely anti and syn. Dihydroxylation using osmium tetroxide progresses with syn stereochemistry.
03:08Hydroboration-Oxidation of Alkenes
In addition to the oxymercuration–demercuration method, which converts the alkenes to alcohols with Markovnikov orientation, a complementary hydroboration-oxidation method yields the anti-Markovnikov product. The hydroboration reaction, discovered in 1959 by H.C. Brown, involves the addition of a B–H bond of borane to an alkene giving an organoborane intermediate. The oxidation of this intermediate with basic hydrogen peroxide forms an alcohol.
01:22Alkenes via Reductive Coupling of Aldehydes or Ketones: McMurry Reaction
The radical dimerization of ketones or aldehydes gives vicinal diols through a pinacol coupling reaction. However, the behavior of titanium metals used for the reaction as a source of electrons is unusual. When the reaction is carried out in the presence of titanium, diols can be isolated at low temperatures. Else titanium further reacts with diols, forming alkenes through the McMurry reaction.
02:38Electrophilic Addition to Alkynes: Halogenation
Introduction
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
02:24Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.