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Catalysis02:50

Catalysis

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.
Autoxidation of Ethers to Peroxides and Hydroperoxides02:23

Autoxidation of Ethers to Peroxides and Hydroperoxides

Ethers represent a class of chemical compounds that become more dangerous with prolonged storage because they tend to form explosive peroxides when standing in the air. Autoxidation is the spontaneous oxidation of a compound in air. In the presence of oxygen, ethers slowly oxidize to form hydroperoxides and dialkyl peroxides.
Regioselectivity of Electrophilic Additions-Peroxide Effect02:35

Regioselectivity of Electrophilic Additions-Peroxide Effect

In the presence of organic peroxides, the addition of hydrogen bromide to an alkene yields the isomer that is not predicted by Markovnikov’s rule. For example, the addition of hydrogen bromide to 2-methylpropene in the presence of peroxides gives 1-bromo-2-methylpropane. This addition reaction proceeds via a free radical mechanism, which reverses the regioselectivity. The free radical reaction mechanism involves three stages: initiation, propagation, and termination.
Oxidation of Alkenes: Syn Dihydroxylation with Potassium Permanganate02:21

Oxidation of Alkenes: Syn Dihydroxylation with Potassium Permanganate

Alkenes can be dihydroxylated using potassium permanganate. The method encompasses the reaction of an alkene with a cold, dilute solution of potassium permanganate under basic conditions to form a cis-diol along with a brown precipitate of manganese dioxide.
Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids02:04

Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids

Diols are compounds with two hydroxyl groups. In addition to syn dihydroxylation, diols can also be synthesized through the process of anti dihydroxylation. The process involves treating an alkene with a peroxycarboxylic acid to form an epoxide. Epoxides are highly strained three-membered rings with oxygen and two carbons occupying the corners of an equilateral triangle. This step is followed by ring-opening of the epoxide in the presence of an aqueous acid to give a trans diol.
Catalysis01:27

Catalysis

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...

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Updated: Jun 30, 2026

Original Experimental Approach for Assessing Transport Fuel Stability
09:48

Original Experimental Approach for Assessing Transport Fuel Stability

Published on: October 21, 2016

粘度对 bis(perfluoro-2-N-propoxypropionyl) 过氧化物在密集的二氧化碳和化溶剂中的热分解的影响.

W C Bunyard1, J F Kadla, J DeYoung

  • 1National Science Foundation Science and Technology Center for Environmentally Responsible Solvents and Processes, Department of Chemistry, University of North Carolina at Chapel Hill, CB 3290, Chapel Hill, North Carolina 27599-3290, USA.

Journal of the American Chemical Society
|July 27, 2001
PubMed
概括

研究了 bis ((perfluoro-2-N-propoxyprionyl) 过氧化物 (BPPP) 的热分解. 密集的二氧化碳对BPPP分解的溶剂效应很小,类似于零粘度条件.

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科学领域:

  • 化学动力学 化学动力学
  • 自由基化学是自由基的化学.
  • 过氧化物分解分解

背景情况:

  • 自由基启动剂在聚合过程中至关重要.
  • 了解溶剂对分解的影响是过程控制的关键.
  • 双二甲-2-N-propoxyprionyl) 过氧化物 (BPPP) 是一个专门的启动剂.

研究的目的:

  • 为了研究BPPP的热分解动力学.
  • 为了评估密集二氧化碳作为溶剂的影响.
  • 为了比较不同化溶剂和启动剂之间的溶剂效应.

主要方法:

  • 在密集的CO2和化溶剂中研究了BPPP的热分解.
  • 测量第一阶分解速率常数 (k ((obs)).
  • 分析了分解激活参数 (和).

主要成果:

  • 在化溶剂中,随着溶剂粘度的下降,k ((obs) 的增加,表明单键裂变.
  • 在密度较高的二氧化碳中,k ((obs) 的比率更高,类似于推断的零粘度率.
  • 激活参数显示了与溶剂粘度的补偿行为.

结论:

  • 密集的二氧化碳对BPPP分解具有最小的溶剂效应.
  • 分解机制在很大程度上独立于密集的CO2中的溶剂粘度.
  • 在密集的二氧化碳中,BPPP的分解动力学与理想的低粘度条件相当.