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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...

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.

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.

Turnover Number and Catalytic Efficiency

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The turnover number of an enzyme is the maximum number of substrate molecules it can transform per unit time. Turnover numbers for most enzymes range from 1 to 1000 molecules per second. Catalase has the known highest turnover number, capable of converting up to 2.8×106 molecules of hydrogen peroxide into water and oxygen per second. Lysozyme has the lowest known turnover number of half a molecule per second.
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Reduction of Alkenes: Catalytic Hydrogenation

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Alkenes undergo reduction by the addition of molecular hydrogen to give alkanes. Because the process generally occurs in the presence of a transition-metal catalyst, the reaction is called catalytic hydrogenation.
Metals like palladium, platinum, and nickel are commonly used in their solid forms — fine powder on an inert surface. As these catalysts remain insoluble in the reaction mixture, they are referred to as heterogeneous catalysts.
The hydrogenation process takes place on the...

Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation

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Introduction
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.

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Updated: Sep 16, 2025

Synthesis and Testing of Supported Pt-Cu Solid Solution Nanoparticle Catalysts for Propane Dehydrogenation

Synthesis and Testing of Supported Pt-Cu Solid Solution Nanoparticle Catalysts for Propane Dehydrogenation

Published on: July 18, 2017

Recent progress of Rh-based three-way catalysts.

Ruize Jiang^1,2, Huilin Wang^1,2, Li Liu^1,2

¹State Key Laboratory of Rare Earth Resource Utilization Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun China.

Smart Molecules : Open Access

|July 8, 2025

Summary

Rhodium (Rh) is crucial for three-way catalysts in gasoline engines, effectively reducing harmful emissions. Future research aims to develop low-cost, high-performance Rh catalysts for stricter environmental standards.

Keywords:

mechanism and kinetics rhodium (Rh) catalysts structure‐activity relationships three‐way catalysts

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The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes

The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes

Published on: April 10, 2015

Area of Science:

Catalysis
Environmental Science
Materials Science

Background:

Three-way catalysts are essential for controlling pollutant emissions from gasoline engines.
Rhodium (Rh) is a key component in these catalysts due to its effectiveness in reducing nitrogen oxides (NOx), carbon monoxide (CO), and hydrocarbons.
Increasingly stringent automotive emission standards necessitate advancements in catalyst technology.

Purpose of the Study:

To systematically review recent developments in Rh-based three-way catalysts.
To explore potential catalyst supports and active center construction strategies.
To summarize the role of Rh in catalytic mechanisms and kinetics.

Main Methods:

Literature review of Rh-based three-way catalysts.
Analysis of catalyst supports and active site engineering.
Summary of Rh's role in catalytic mechanisms and kinetics.

Main Results:

Rhodium exhibits superior NOx elimination and high N2 selectivity.
Rh simultaneously eliminates CO and hydrocarbons.
Recent developments focus on support materials and active center design.

Conclusions:

A deep understanding of Rh-based catalysts is crucial for future advancements.
Future opportunities lie in designing low-cost Rh catalysts with enhanced low-temperature performance.
Rh remains an irreplaceable element for effective automotive emission control.