H

Hydrogenation

C=C + H₂ → C–C
Quick Reference
Formula / NotationC=C + H₂ → C–C
Also Known AsCatalytic hydrogenation, reduction by hydrogen, catalytic reduction, hydration of double bond

What is Hydrogenation?

Hydrogenation is a chemical reaction in which hydrogen gas (H₂) is added across an unsaturated bond (C=C, C≡C, C=O, C≡N) in the presence of a catalyst. It is used extensively to convert unsaturated fats to saturated fats, to produce ammonia (indirectly), and in petroleum refining. Catalytic hydrogenation typically uses nickel, palladium, or platinum catalysts.

Formula & Notation

C=C + H₂ → C–C

Other Names / Synonyms: Catalytic hydrogenation, reduction by hydrogen, catalytic reduction, hydration of double bond

Properties & Characteristics

Requires catalyst: Ni (Raney Ni), Pd, Pt, Rh. Temperature: 25–300°C depending on substrate. Pressure: 1–100 atm H₂. Alkene + H₂ → alkane (Pd/C, 25°C, 1 atm). Ketone + H₂ → alcohol. Benzene + 3H₂ → cyclohexane (higher T, P). Syn-addition (H₂ adds to same face). Exothermic reaction.

Uses & Applications

Food industry (vegetable oil hardening for margarine and shortening). Petroleum refining (removing sulfur, saturation of aromatics). Pharmaceutical synthesis (reducing functional groups). Plastics and polymers (cyclohexane from benzene). Fischer-Tropsch process (syngas to fuels). Fine chemical synthesis.

Safety Information

Highly flammable H₂ under pressure — explosion risk. Pyrophoric catalysts (Raney Ni, Pd/C dry) — ignite spontaneously in air. High-pressure reactors — mechanical hazards. Hydrogen embrittlement of reactor vessels. Partially hydrogenated oils produce trans fats — health concerns. Keep catalyst moist before adding to reaction.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Hydrogenation
Formula C=C + H₂ → C–C
Synonyms Catalytic hydrogenation, reduction by hydrogen, catalytic reduction, hydration of double bond

Frequently Asked Questions

Hydrogenation is a chemical reaction in which hydrogen gas (H₂) is added across an unsaturated bond (C=C, C≡C, C=O, C≡N) in the presence of a catalyst. It is used extensively to convert unsaturated fats to saturated fats, to produce ammonia (indirectly), and in petroleum refining. Catalytic hydrogenation typically uses nickel, palladium, or platinum catalysts.

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