在增加分子内反应率中的作用
Anthony A Armstrong1, L Mario Amzel
1Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205-2185, USA.
Journal of the American Chemical Society
|November 20, 2003
概括
可访问的基层和过渡状态之间的差异显著影响了分子内凝结反应速率. 形态,而不是振动,是这些反应中激活自由能量的关键驱动因素.
科学领域:
- 有机化学 有机化学
- 物理化学 物理化学
- 化学动力学 化学动力学
背景情况:
- 内分子凝聚反应在有机合成中至关重要.
- 众所周知,反应速率受到反应分子的结构的影响.
研究的目的:
- 为了研究二氧化酸单分子内凝聚率变化的热起源.
- 为了确定构造和振动对激活自由能量的贡献.
主要方法:
- 基态适配体和过渡状态类适配体之间的差 (DeltaS(NAC,S)) 的估计.
- 估计的DeltaS ((NAC,S) 和实验确定的反应速率常数之间的相关性分析.
- 正常模式分析以评估振动贡献.
主要成果:
- 在DeltaS(NAC,S) 和反应速率 (R(2) = 0.96和0.73之间观察到强烈的相关性.
- 正常模式分析表明,振动变化的贡献很小.
- 发现符合性的差异是显著的.
结论:
- 基本状态和过渡状态之间的合规差异是激活的自由能量的一个主要因素.
- 这项研究阐明了控制分子内凝聚反应动力学的热因子.
相关概念视频
02:55Temperature Dependence on Reaction Rate
The Collision Theory
Atoms, molecules, or ions must collide before they can react with each other. Atoms must be close together to form chemical bonds. This premise is the basis for a theory that explains many observations regarding chemical kinetics, including factors affecting reaction rates.
The collision theory is based on the postulates that (i) the reaction rate is proportional to the rate of reactant collisions, (ii) the reacting species collide in an orientation allowing contact between...
Atoms, molecules, or ions must collide before they can react with each other. Atoms must be close together to form chemical bonds. This premise is the basis for a theory that explains many observations regarding chemical kinetics, including factors affecting reaction rates.
The collision theory is based on the postulates that (i) the reaction rate is proportional to the rate of reactant collisions, (ii) the reacting species collide in an orientation allowing contact between...
02:50Catalysis
The presence of a catalyst affects the rate of a chemical reaction. A catalyst is a substance that can increase the reaction rate without being consumed during the process. A basic comprehension of a catalysts’ role during chemical reactions can be understood from the concept of reaction mechanisms and energy diagrams.
02:28Effect of Temperature Change on Reaction Rate
The Arrhenius equation,
01:13Introduction to Mechanisms of Enzyme Catalysis
For many years, scientists thought that enzyme-substrate binding took place in a simple "lock-and-key" fashion. This model stated that the enzyme and substrate fit together perfectly in one instantaneous step. However, current research supports a more refined view scientists call induced fit. The induced-fit model expands upon the lock-and-key model by describing a more dynamic interaction between enzyme and substrate. As the enzyme and substrate come together, their interaction causes a mild...
01:22Factors Influencing the Rate of Chemical Reactions
A variety of factors influence the rate of chemical reactions. For a chemical reaction to happen, atoms must collide with enough energy to overcome the repulsion between their electrons. This energy is called activation energy. Factors influencing the rate of reaction either lower the activation energy or increase the likelihood of a successful collision.
Concentration and Pressure:
The more particles present within a given space, the more likely those particles are to bump into one another.
Concentration and Pressure:
The more particles present within a given space, the more likely those particles are to bump into one another.
01:27Catalysis
Catalysis influences the rate of chemical reactions by providing an alternative reaction pathway with lower activation energy. A catalyst speeds up a reaction, but it is not consumed during the process. The fundamental principle of catalysis is the ability of a catalyst to alter the reaction mechanism, often introducing a more efficient pathway than the uncatalyzed process.In a catalyzed reaction, the catalyst participates directly in the reaction mechanism. It interacts with reactants to form...