键对来自的质子偶联电子转移的动态效应
Martin Sjödin1, Tania Irebo, Josefin E Utas
1Department of Photochemistry and Molecular Science, Uppsala University, Box 523, SE-751 20 Uppsala, Sweden.
Journal of the American Chemical Society
|October 5, 2006
概括
研究了涉及醇的质子合电子转移 (PCET) 反应. 键显著降低反应障碍,促进生物系统中高效的PCET.
科学领域:
- 物理化学 物理化学
- 化学动力学 化学动力学
- 摄影化学的使用.
背景情况:
- 质子合电子转移 (PCET) 在生物过程中至关重要.
- 了解PCET机制是设计高效催化剂的关键.
- 键在PCET动力学中的作用需要进一步阐明.
研究的目的:
- 研究PCET的动力学和机制,从到氧化剂.
- 确定分子内键对PCET通路的影响.
- 探索生物系统中观察到的机制的一般适用性.
主要方法:
- 激光闪光的光解产生一个[Ru(bpy) ((3))) ((3+) 氧化剂.
- 在水溶液中氧化作用的动力学研究.
- 对pH依赖率和马库斯自由能量关系的分析.
主要成果:
- PCET采用了一种协调的电子-质子转移 (CEP) 机制.
- 内分子键通过促进质子向基的转移消除了pH依赖性.
- 键减少了重组能量,降低了反应屏障.
- 机制从逐步转向使用较弱氧化剂的CEP.
结论:
- 协同的电子-质子转移是由分子内键促进的.
- 结合提供了一个一般的机制来降低酶和模型复合体中的PCET障碍.
- 这种机制在较低的驱动力下促进有效的PCET,这与生物系统有关.
相关概念视频
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In the presence of oxidizing agents, phenols are oxidized to quinones. Quinones can be easily reduced back to phenols using mild reducing agents. The electron-donating hydroxyl group enhances the reactivity of the aromatic ring, enabling oxidation of the ring even in the absence of an α hydrogen.
o-hydroxy phenols are oxidized to o-quinones and p-hydroxy phenols to p-quinones. Such redox reactions involve the transfer of two electrons and two protons. The reversible redox property is crucial in...
o-hydroxy phenols are oxidized to o-quinones and p-hydroxy phenols to p-quinones. Such redox reactions involve the transfer of two electrons and two protons. The reversible redox property is crucial in...
Acidity and Basicity of Alcohols and Phenols
Like water, alcohols are weak acids and bases. This is attributed to the polarization of the O–H bond making the hydrogen partially positive. Moreover, the electron pairs on the oxygen atom of alcohol make it both basic and nucleophilic. Protonation of an alcohol converts hydroxide, a poor leaving group, into water—a good one. The two acid–base equilibria corresponding to ethanol are depicted below.
Benzene to Phenol via Cumene: Hock Process
The synthesis of phenol from benzene via cumene and cumene hydroperoxide is called the Hock process. First, a Friedel–Crafts alkylation reaction of benzene with propene gives cumene. Then cumene forms cumene hydroperoxide via a radical chain reaction. In the chain initiation step, the benzylic hydrogen is abstracted to give a benzylic radical. In the chain propagation step, the benzylic radical reacts with an oxygen diradical to form a cumene hydroperoxide radical. The cumene hydroperoxide...
Hydrogen Bonds
Hydrogen BondsHydrogen bonds are weak attractions between atoms that have formed other chemical bonds. One of these atoms is electronegative, like oxygen, and has a partial negative charge. The other is a hydrogen atom that has bonded with another electronegative atom and has a partial positive charge.Hydrogen Bonds Control the World!Because hydrogen has very weak electronegativity when it binds with a strongly electronegative atom, such as oxygen or nitrogen, electrons in the bond are...
Hydrogen Bonds
A hydrogen bond is formed when a weakly positive hydrogen atom already bonded to one electronegative atom (for example, the oxygen in the water molecule) is attracted to another electronegative atom from another polar molecule, such as water (H2O), hydrogen fluoride (HF), or ammonia (NH3). The huge electronegativity difference between the H atom (2.1) and the atom to which it is bonded (4.0 for an F atom, 3.5 for an O atom, or 3.0 for an N atom), combined with the very small size of an H atom...
Physical Properties of Alcohols and Phenols
Alcohols are organic compounds in which a hydroxy group is attached to a saturated carbon. Phenols are a class of alcohols containing a hydroxy group attached to an aromatic ring. The physical properties of the alcohols and phenols are influenced by hydrogen bonding due to the oxygen–hydrogen dipole in the hydroxy functional group and dispersion forces between alkyl or aryl regions of alcohol and phenol molecules.
Alcohols possess a higher boiling point than aliphatic hydrocarbons of similar...
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