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Catalysis

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.

Reduction of Alkenes: Asymmetric Catalytic Hydrogenation

Reduction of Alkenes: Asymmetric Catalytic Hydrogenation

Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...

Radical Reactivity: Overview

Radical Reactivity: Overview

Radicals, the highly reactive species, gain stability by undergoing three different reactions. The first reaction involves a radical-radical coupling, in which a radical combines with another radical, forming a spin‐paired molecule. The second reaction is between a radical and a spin‐paired molecule, generating a new radical and a new spin‐paired molecule. The third reaction is radical decomposition in a unimolecular reaction, forming a new radical and a spin‐paired...

Radical Reactivity: Steric Effects

Radical Reactivity: Steric Effects

The presence of electron-donating, electron-withdrawing, or conjugating groups adjacent to a radical center, imparts electronic stabilization to the radicals. Examples of such electronically-stabilized radicals are triphenylmethyl, tetramethylpiperidine‐N‐oxide, and 2,2‐diphenyl‐1‐picrylhydrazyl. These radicals are remarkably stable and are known as persistent radicals. Some of the persistent radicals can even be isolated and purified.
Along with electronic...

Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation

Reduction 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.

Factors Influencing the Rate of Chemical Reactions

Factors 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....

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Related Experiment Video

Updated: Nov 30, 2025

Catalytic Reactions at Amine-Stabilized and Ligand-Free Platinum Nanoparticles Supported on Titania During Hydrogenation of Alkenes and Aldehydes

Catalytic Reactions at Amine-Stabilized and Ligand-Free Platinum Nanoparticles Supported on Titania During Hydrogenation of Alkenes and Aldehydes

Published on: June 24, 2022

Atomically Dispersed Pt-group Catalysts: Reactivity, Uniformity, Structural Evolution, and Paths to Increased

Joaquin Resasco¹, Phillip Christopher¹

¹Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California 93117, United States.

The Journal of Physical Chemistry Letters

|November 16, 2020

Summary

Atomically dispersed platinum-group metals on oxide supports show unique reactivity compared to clusters. Uniform metal sites are crucial for precise catalytic property assessment and single-site behavior in catalysis.

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Catalytic Reactions at Amine-Stabilized and Ligand-Free Platinum Nanoparticles Supported on Titania During Hydrogenation of Alkenes and Aldehydes

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Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

Published on: April 10, 2018

Area of Science:

Catalysis
Materials Science
Surface Chemistry

Background:

Renewed interest in atomically dispersed metal catalysts due to advanced characterization tools.
Focus on platinum-group metals supported on oxides for catalytic applications.

Purpose of the Study:

To present an approach for synthesizing and understanding atomically dispersed platinum-group metals on oxide supports.
To highlight the importance of uniform metal sites for accurate catalytic assessment and single-site behavior.

Main Methods:

Site-specific characterization techniques to differentiate single atoms from clusters.
Methods for assessing the uniformity of metal sites on supports.
Atomic-scale structural analysis and in-situ/operando studies.

Main Results:

Atomically dispersed metal species exhibit distinct reactivity compared to metal clusters.
Uniform local coordination at metal sites is essential for predictable catalytic performance.
Uniformity enables atomic-scale structural elucidation and understanding of dynamic evolution.

Conclusions:

Achieving uniform, single-atom metal sites is key to unlocking precise catalytic control and enhanced functionality.
Controlling the coordination and steric environment of single sites, along with promoting site cooperativity, offers pathways to advanced catalyst design.