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Example: acid-base reaction of acetic acid and water. Red arrows: deprotonation of acetic acid; green arrows: protonation of the acetate with formation of acetic acid.

In chemistry, protonation refers to the addition of protons ( hydrogen nuclei / cations ) to a chemical compound as part of an acid-base reaction . One or more positive charges are added to the target molecule, depending on the number of protons transferred . The compound that has taken up the protons is called the protonated compound . The opposite process, the splitting off of protons from a compound, is called deprotonation .

Protonation of compound B by the acid HA , which is deprotonated in the process.

The prerequisite for the process of protonation is the presence of an acid and a base as defined by Brønsted and Lowry . The acid strength - represented by the pK S value - and the base strength ( pK B ) determine whether the balance on the side of the protonated or unprotonated compound is.

The protonation of a compound can be influenced by steric factors.

A positive charge is transferred with the proton, as in the following example, which shows the protonation of ammonia (NH 3 ) by hydrogen chloride (HCl):

Hydrogen chloride gives off a proton to the ammonia molecule. This is a negatively charged are chloride - anion and a positively charged ammonium - cation formed.

Protonation is a reaction step that has been widely observed and used. It is often used to activate a chemical compound for subsequent reactions . But they are also used to ionize compounds , for example in the context of a mass spectrometric analysis.

See also

Individual evidence

  1. Albert Gossauer: Structure and reactivity of biomolecules an introduction to organic chemistry . John Wiley & Sons, 2006, ISBN 3-906390-29-2 , pp. 572,578 ( limited preview in Google Book Search).
  2. Hartmut Follmann, Walter Grahn: Chemistry for biologists internship and theory . Springer-Verlag, 2013, ISBN 978-3-322-80146-3 , pp. 43 ( limited preview in Google Book search).
  3. James Huheey, Ellen Keiter, Richard Keiter: Inorganic chemistry principles of structure and reactivity . Walter de Gruyter GmbH & Co KG, 2014, ISBN 978-3-11-030795-5 , p. 374 ( limited preview in Google Book search).
  4. Michael Quednau: Applications from Urban Mining to NanoGeoScience . Walter de Gruyter GmbH & Co KG, 2017, ISBN 978-3-11-042287-0 , p. 167 ( limited preview in Google Book search).
  5. Jürgen H. Gross: Mass Spectrometry A Textbook . Springer-Verlag, 2012, ISBN 978-3-8274-2981-0 , pp. 387 ( limited preview in Google Book search).