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 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
Step 2: Adsorption of gaseous reactants to the metal surface
Step 3: Addition of hydrogen to the double bond
Step 4: Desorption of the gaseous product
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.
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 gives cyclohexane.
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.
