Hydrogenation Definition in Chemistry

Chemistry Glossary Definition of Hydrogenation

Margarine is an example of a product made via hydrogenation.
Margarine is an example of a product made via hydrogenation. milanfoto / Getty Images

Hydrogenation is a reduction reaction which results in an addition of hydrogen (usually as H2). If an organic compound is hydrogenated, it becomes more "saturated" with hydrogen atoms. The process typically requires the use of a catalyst, since hydrogenation only occurs spontaneously at high temperatures. The most common catalysts are nickel, platinum, or palladium.

Hydrogenation reduces the number of double and triple bonds in hydrocarbons, while dehydrogenation removes hydrogen atoms and increases the number of double and triple bonds.

Key Takeaways: Hydrogenation Definition

  • Hydrogenation is a chemical reaction that adds hydrogen to a molecule.
  • Hydrogenation is not thermodynamically favorable at ordinary temperatures, so a catalyst is needed. Usually this catalyst is a metal.
  • Examples of hydrogenated products include margarine, mineral turpentine, and aniline.

Hydrogenation Uses

Hydrogenation has many applications, but most people are familiar with the reaction as the one used to make liquid oils into semi-solid and solid fats. There may be some health concerns associated with hydrogenation of unsaturated dietary fats to produce saturated fats and trans fats.


  • Berkessel, Albrecht; Schubert, Thomas J. S.; Müller, Thomas N. (2002). "Hydrogenation without a Transition-Metal Catalyst: On the Mechanism of the Base-Catalyzed Hydrogenation of Ketones". Journal of the American Chemical Society. 124 (29): 8693–8. doi:10.1021/ja016152r
  • Hudlický, Miloš (1996). Reductions in Organic Chemistry. Washington, D.C.: American Chemical Society. p. 429. ISBN 978-0-8412-3344-7.
  • Jang, E.S.; Jung, M.Y.; Min, D.B. (2005). "Hydrogenation for Low Trans and High Conjugated Fatty Acids". Comprehensive Reviews in Food Science and Food Safety.
  • Kummerow, Fred August; Kummerow, Jean M. (2008). Cholesterol Won't Kill You, But Trans Fat Could. Trafford. ISBN 978-1-4251-3808-0.
  • Rylander, Paul N. (2005). "Hydrogenation and Dehydrogenation" in Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH, Weinheim. doi:10.1002/14356007.a13_487
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Helmenstine, Anne Marie, Ph.D. "Hydrogenation Definition in Chemistry." ThoughtCo, Jul. 29, 2021, thoughtco.com/definition-of-hydrogenation-604530. Helmenstine, Anne Marie, Ph.D. (2021, July 29). Hydrogenation Definition in Chemistry. Retrieved from https://www.thoughtco.com/definition-of-hydrogenation-604530 Helmenstine, Anne Marie, Ph.D. "Hydrogenation Definition in Chemistry." ThoughtCo. https://www.thoughtco.com/definition-of-hydrogenation-604530 (accessed March 23, 2023).