Related Experiment Video
Updated: May 29, 2026
13:38
Synthesis of Biocompatible Liquid Crystal Elastomer Foams as Cell Scaffolds for 3D Spatial Cell Cultures
Published on: April 11, 2017
Ethylene epoxidation catalyzed by chlorine-promoted silver oxide
M O Ozbek1, I Onal, R A Van Santen
1Chemical Engineering Department, Middle East Technical University, 06531, Ankara, Turkey.
Journal of Physics. Condensed Matter : an Institute of Physics Journal
|September 21, 2011
Summary
Direct ethylene oxide (EO) formation is possible on silver oxide surfaces. This selective reaction pathway avoids acetaldehyde (AA) byproduct formation, unlike pathways involving oxometallacycle intermediates.
Area of Science:
- Heterogeneous catalysis
- Surface chemistry
- Oxidation reactions
Background:
- Ethylene oxide (EO) is a key industrial chemical.
- Selective oxidation of ethylene to EO is challenging.
- Silver-based catalysts are widely used for ethylene oxidation.
Purpose of the Study:
- To investigate the direct formation of ethylene oxide (EO) on a silver oxide surface.
- To understand the reaction mechanism and identify factors influencing EO selectivity.
- To explore methods for enhancing EO selectivity by suppressing competing pathways.
Main Methods:
- Theoretical investigation of reaction pathways.
- Density Functional Theory (DFT) calculations.
- Analysis of surface intermediates and transition states.
Main Results:
- Direct reaction of gas-phase ethylene with surface oxygen on silver oxide forms EO selectively.
- The direct pathway avoids the formation of acetaldehyde (AA).
- Oxometallacycle (OMC) intermediates, formed on oxygen-vacant sites, reduce EO selectivity.
- Chlorine (Cl) adsorption blocks oxygen-vacant sites, preventing OMC formation and enhancing EO selectivity.
Conclusions:
- Direct ethylene oxidation on silver oxide offers a selective route to EO.
- Controlling surface oxygen vacancy sites is crucial for maximizing EO selectivity.
- Surface modification, such as Cl adsorption, can effectively suppress undesired pathways.
Related Concept Videos
03:00Preparation of Epoxides
Overview
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...
02:24Acid-Catalyzed Ring-Opening of Epoxides
Epoxides that are three-membered ring systems are more reactive than other cyclic and acyclic ethers. The high reactivity of epoxides originates from the strain present in the ring. This ring strain acts as a driving force for epoxides to undergo ring-opening reactions either with halogen acids or weak nucleophiles in the presence of mild acid. The acid catalyst converts the epoxide oxygen, a poor leaving group, into an oxonium ion, a better leaving group, making the reaction feasible. The...
02:57Sharpless Epoxidation
The conversion of allylic alcohols into epoxides using the chiral catalyst was discovered by K. Barry Sharpless and is known as Sharpless epoxidation. The use of a chiral catalyst enables the formation of one enantiomer of the product in excess. This chiral catalyst is mainly a chiral complex of titanium tetraisopropoxide and tartrate ester (specific stereoisomer). The stereoisomer used in the chiral catalyst dictates the formation of the enantiomer of the product. In other words, the use of...
02:04Oxidation 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.
02:26Base-Catalyzed Ring-Opening of Epoxides
Due to their highly strained structures, epoxides can readily undergo ring-opening reactions through nucleophilic substitution, either in the presence of an acid or a base. The nucleophilic substitution reactions in the presence of acid are called acid-catalyzed ring-opening reactions, and nucleophilic substitution reactions in the presence of a base are called base-catalyzed ring-opening reactions. Epoxides undergo base-catalyzed ring-opening reactions in the presence of a strong nucleophile...
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.