Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/12/27 13:01:52」(JST)

wiki en

In chemistry, protonation is the addition of a proton (H⁺) to an atom, molecule, or ion, forming the conjugate acid.^[1] Some classic examples include

the protonation of water by sulfuric acid:

the protonation of isobutene in the formation of a carbocation:

=

the protonation of ammonia in the formation of ammonium chloride from ammonia and hydrogen chloride:

Protonation is a fundamental chemical reaction and is a step in many stoichiometric and catalytic processes. Some ions and molecules can undergo more than one protonation and are labeled polybasic, which is true of many biological macromolecules. Protonation and deprotonation occur in most acid-base reactions; they are the core of most acid-base reaction theories. A Bronsted-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. Protonating or deprotonating a molecule or ion alters many chemical properties beyond the change in the charge and mass: hydrophilicity, reduction potential, optical properties, among others. Protonation is also an essential step in certain analytical procedures such as electrospray mass spectrometry.

Rates of protonation and deprotonation[edit]

Protonations are often rapid, in part because of the high mobility of protons in water. The rate of protonation is related to the acidity of the protonated species, in that weak acids deprotonate more slowly than strong acids. The rates of protonation and deprotonation can be especially slow when protonation induces significant structural changes.^[2]

Reversibility and catalysis[edit]

Usually, protonations are reversible and the conjugate base is unchanged by being protonated. In some cases protonation induces isomerization, however. Cis-alkenes can be converted to trans-alkenes using a catalytic amount of protonating agent. Many enzymes, such as the serine hydrolases, operate by mechanisms that involve reversible protonations of substrates.

References[edit]

^ Zumdahl, S. S. “Chemistry” Heath, 1986: Lexington, MA. ISBN 0-669--04529-2.
^ Kramarz, K. W.; Norton, J. R. (1994). "Slow Proton Transfer Reactions in Organometallic and Bioinorganic Chemistry". Progress in Inorganic Chemistry 42: 1–65.

English Journal

pH-Tunable wormlike micelles based on an ultra-long-chain "pseudo" gemini surfactant.

Feng Y1, Chu Z.
Soft matter.Soft Matter.2015 Jun 3;11(23):4614-20. doi: 10.1039/c5sm00677e.
Smart surfactant wormlike micelles (SWLMs), responsive to external stimuli, are a particularly recent area of development, yet highly promising, given the versatility of the materials but simplicity of the design. Here, we developed a pH-switchable wormlike micellar system based on a "pseudo" gemini
PMID 25959441
PMID 25964989

Protic anions [H(B12X12)]- (X = F, Cl, Br, I) that act as Brønsted acids in the gas phase.

Jenne C1, Keßler M, Warneke J.
Chemistry (Weinheim an der Bergstrasse, Germany).Chemistry.2015 Apr 7;21(15):5887-91. doi: 10.1002/chem.201500034. Epub 2015 Mar 3.
The acidity of protic cations and neutral molecules has been studied extensively in the gas phase, and the gas-phase acidity has been established previously as a very useful measure of the intrinsic acidity of neutral and cationic compounds. However, no data for any anionic acids were available prio
PMID 25735766

Japanese Journal

A Catalytic asymmetric Strecker-Type Reaction Promoted by Lewis Acid-Lewis Base Bifunctional Catalvst

Takamura Masahiro,Hamashima Yoshitaka,usuda Hiroyuki [他],KANAI Motomu,SHIBASAKI Masakatsu
Chemical & pharmaceutical bulletin 48(10), 1586-1592, 2000-10-01
… From the mechanistic studies including kinetic and NMR experiments of the catalytic species, the role of PhOH seems to be a proton source to protonate the anionic nitrogen of the intermediate. …
NAID 110003635332