Editing Protonation (section)

{{short description|Addition of a proton to an atom, molecule, or ion, forming the conjugate acid}}
In chemistry, '''protonation''' (or '''hydronation''') is the adding of a [[proton#Hydrogen ion|proton]] (or [[hydron (chemistry)|hydron]], or hydrogen cation), usually denoted by H<sup>+</sup>, to an [[atom]], [[molecule]], or [[ion]], forming a [[conjugate acid]].<ref>{{cite book|last=Zumdahl|first=S. S.|title=Chemistry|publisher=Heath|date=1986|location=Lexington, MA|ISBN=0-669-04529-2}}</ref> (The complementary process, when a proton is removed from a [[Brønsted–Lowry acid–base theory|Brønsted–Lowry acid]], is [[deprotonation]].) Some examples include
* The protonation of [[water]] by [[sulfuric acid]]:
*: H<sub>2</sub>SO<sub>4</sub> + H<sub>2</sub>O {{eqm}} H<sub>3</sub>O<sup>+</sup> + {{chem|HSO|4|-}}
* The protonation of [[isobutene]] in the formation of a [[carbocation]]:
*: (CH<sub>3</sub>)<sub>2</sub>C=CH<sub>2</sub> + HBF<sub>4</sub> {{eqm}} (CH<sub>3</sub>)<sub>3</sub>C<sup>+</sup> + {{chem|BF|4|-}}
* The protonation of [[ammonia]] in the formation of [[ammonium chloride]] from ammonia and [[hydrogen chloride]]:
*: NH<sub>3</sub>([[gas|g]]) + HCl([[gas|g]]) → NH<sub>4</sub>Cl([[solid|s]])

Protonation is a fundamental chemical reaction and is a step in many [[stoichiometry|stoichiometric]] and [[catalysis|catalytic processes]]. Some ions and molecules can undergo more than one protonation and are labeled polybasic, which is true of many biological [[macromolecule]]s. Protonation and deprotonation (removal of a proton) occur in most [[acid–base reaction]]s; they are the core of most acid–base reaction theories. A [[Brønsted–Lowry acid–base theory|Brønsted–Lowry acid]] is defined as a [[chemical substance]] that protonates another substance. Upon protonating a substrate, the mass and the charge of the species each increase by one unit, making it an essential step in certain analytical procedures such as electrospray [[mass spectrometry]]. Protonating or deprotonating a molecule or ion can change many other chemical properties, not just the charge and mass, for example [[solubility]], [[hydrophile|hydrophilicity]], [[reduction potential]] or [[oxidation potential]], and [[ultraviolet–visible spectroscopy|optical properties]] can change.