Catalytic Hydrogenation: Mechanism and Application

Table of Contents

Catalytic hydrogenation, examples, mechanisms, and applications in organic chemistry have been discussed here:

Catalytic hydrogenation Definition

Catalytic hydrogenation is the addition of molecular hydrogen to carbon-carbon multiple bonds in the presence of transition metal catalysts such as Ni, Pt, Pd, Ru, Rh, etc., or their compounds. Platinum or platinum from PtO2, palladium, ruthenium, or rhodium is common components of the noble metal catalysts used for low-pressure hydrogenations, while catalyst like Raney nickel, copper chromite, and ruthenium supported on carbon or alumina are employed for reasonably high hydrogen pressure. In the hydrogenation apparatus, inert supports like carbon, alumina, barium sulphate, calcium carbonate, etc. are used as surfaces on which palladium, ruthenium, or rhodium catalysts are coated.

The solvents frequently employed for hydrogenation are ethyl acetate, ethanol, methanol, acetic acid, perchloric acid, etc. Like Birch reduction, Cannizzaro reaction, metal hydride reduction, Clemmensen reduction, it is also one of the reduction reactions.

Catalytic hydrogenation Examples

Some of the examples of catalytic hydrogenations are:

catalytic hydrogenation examples

Catalytic hydrogenation mechanism

The reaction is thought to involve chemisorption exothermic adsorption of gases by solids, which results in the formation of a chemical bond between the adsorbing and adsorbed materials. The adsorbing materials, in this case, are a finely divided solid transition metal with a large surface area, hydrogen gas, and an unsaturated compound in the gaseous state, as well as the adsorbed materials.

Catalytic hydrogenation of alkene

The mechanism of catalytic hydrogenation of alkene involving gaseous reactants and products can be described in the following steps:

Step 1: Diffusion of gases reactants, hydrogen, and alkene

catalytic hydrogenation of alkene, catalytic hydrogenation mechanism

Step 2: Adsorption of gaseous reactants to the metal surface

catalytic hydrogenation of alkene, catalytic hydrogenation mechanism

Step 3: Addition of hydrogen to the double bond

catalytic hydrogenation of alkene, catalytic hydrogenation mechanism

Step 4: Desorption of the gaseous product

catalytic hydrogenation of alkene, catalytic hydrogenation mechanism

Step 5: Diffusion of the product, the alkane

Catalytic hydrogenation of aldehydes and ketones

When aldehydes and ketones undergo catalytic hydrogenation, alcohol is obtained as a product. Aldehyde produces primary alcohol, while ketones produce secondary alcohol. Nickel, palladium, or platinum are among the commonly used catalysts for the catalytic hydrogenation of aldehydes and ketones.

catalytic hydrogenation of aldehyde and ketone

Application of catalytic hydrogenation

Since the reactions involve the addition of hydrogen (H2) to carbon-carbon multiple bonds, catalytic hydrogenation reaction has much industrial and analytical importance.

  • Determination of the amount of an unsaturated compound and the number of unsaturated (double or triple bond) per mole of the compound.
  • Applicable for the hydrogenation of fats and oils in industries.

Catalytic hydrogenation reaction video

FAQs/MCQs

catalytic hydrogenation of oil results in the production of

catalytic hydrogenation of oil results in the production of margarine.

catalytic hydrogenation of benzene

catalytic hydrogenation of benzene

Catalytic hydrogenation of benzene gives cyclohexane.

catalytic hydrogenation of ethene

catalytic hydrogenation of ethene

The catalytic hydrogenation of ethene gives ethane

catalytic hydrogenation of ethyne

During catalytic hydrogenation, ethyne is first converted into ethene, and on further reduction ethane is obtained.

References

  • Morrison, R. T., & Boyd, R. N., Organic chemistry, Allyn and Bacon, Inc. 1987.
  • March, J., Advanced Organic Chemistry, Wiley Eastern Limited, 1986.
  • Skyes, P., A Guide Book to Mechanism in Organic Chemistry, Second edition, Orient Longman Ltd., 1988.

Catalytic Hydrogenation Mechanism and Application, catalytic hydrogenation reaction, catalytic hydrogenation mechanism

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