In acid catalysis and base catalysis a chemical reaction is catalized by an acid or a base. The acid is often the proton and the base is often a hydroxyl ion. Typical reactions catalysed by proton transfer are esterfications and aldol reactions. In these reactions the conjugate acid of the carbonyl group is a better electrophile than the neutral carbonyl group itself. Catalysis by either acid or base can occur in two different ways: specific catalysis and general catalysis. A chemical reaction is a process involving one, two or more substances (called reactants), characterized by a chemical change and yielding one or more product(s) which are different from the reactants. ... In chemistry and biology, catalysis is the acceleration of the reaction rate of a chemical reaction by means of a substance, called a catalyst, that is itself unchanged chemically by the overall reaction. ... An acid (often represented by the generic formula AH) is typically a water-soluble, sour-tasting chemical compound. ... The common (Arrhenius) definition of a base is a chemical compound that either donates hydroxide ions or absorbs hydrogen ions when dissolved in water. ... Hydronium is the common name for the cation H3O+. Nomenclature According to IUPAC ion nomenclature, it should be referred to as oxonium. ... Hydroxide is a functional group consisting of oxygen and hydrogen: -O−H It has a charge of 1-. The term hydroxyl group is used when the functional group -OH is counted as a substituent of an organic compound. ... Esterification is the general name for a chemical reaction in that an ester is the reaction product. ... An aldol reaction takes the following form: 2 enolate anions ↔ aldol The reaction requires a base catalyst. ... In the Brønsted-Lowry (protonic) theory of acids and bases, a conjugate acid is the acid member, HX, of a pair of two compounds that transform into each other by gain or loss of a proton. ... In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom. ... In chemistry, an electrophile (literally electron-lover) is a reagent attracted to electrons that participates in a chemical reaction by accepting an electron pair in order to bond to a nucleophile. ...

In specific acid catalysis taking place in solvent S , the reaction rate is proportional to the concentration of the protonated solvent molecules SH⁺. The acid catalyst itself (AH) only contributes to the rate acceleration by shifting the chemical equilibrium between solvent S and AH in favor of the SH⁺ species. The reaction rate for a reactant or product in a particular reaction is defined as the amount (in moles or mass units) per unit time per unit volume that is formed or removed. ... Concentration is a very common concept used in chemistry and related fields. ... Chemical equilibrium is the state in which a chemical reaction proceeds at the same rate as its reverse reaction; the rates of the forward and reverse reactions are equal, and the concentration of the reactants and products stop changing. ...

S + AH → SH⁺ + A^-

For example in an aqueous buffer solution the reaction rate for reactants R depends on the pH of the system but not on the concentrations of different acids. Buffer solutions are solutions which resist change in pH upon addition of small amounts of acid or base. ... The title of this article begins with a capital letter, due to technical limitations of the MediaWiki software. ... Concentration is a very common concept used in chemistry and related fields. ...

This type of chemical kinetics is observed when reactant R₁ in a fast equilibrium with its conjugate base R₁H⁺ which proceeds to react slowly with R₂ to the reaction product for example in the acid catalysed aldol reaction. In physical chemistry, chemical kinetics or reaction kinetics study reaction rates in a chemical reaction. ... An aldol reaction takes the following form: 2 enolate anions ↔ aldol The reaction requires a base catalyst. ...

In general acid catalysis all species capable of donating protons contribute to reaction rate acceleration. The strongest acids are most effective. Reactions in which proton transfer is rate-determining exhibit general acid catalysis, for example diazonium coupling reactions. The reaction rate for a reactant or product in a particular reaction is defined as the amount (in moles or mass units) per unit time per unit volume that is formed or removed. ... An azo coupling is an organic reaction between a diazonium compound and an aniline or a phenol. ...

When keeping the pH at a constant level but changing the buffer concentration a change in rate signals a general acid catalysis. A constant rate is evidence for a specific acid catalyst.