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In chemistry, an acid dissociation constant (also known as acidity constant, or acid-ionization constant; denoted ) is a quantitative measure of the strength of an acid in solution. It is the equilibrium constant for a chemical reaction
See Amino acid for the pK a values of all amino acid side chains inferred in such a way. There are also numerous experimental studies that have yielded such values, for example by use of NMR spectroscopy. The table below lists the model pK a values that are often used in a protein pK a calculation, and contains a third column based on protein ...
For example, hydrochloric acid is a weak acid in solution in pure acetic acid, HO 2 CCH 3, which is more acidic than water. HO 2 CCH 3 + HCl ⇌ (HO) 2 CCH + 3 + Cl −. The extent of ionization of the hydrohalic acids decreases in the order HI > HBr > HCl. Acetic acid is said to be a differentiating solvent for the three acids, while water is ...
Serine ball and stick model spinning. Serine (symbol Ser or S) [3] [4] is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated − NH +
Strong acids, such as sulfuric or phosphoric acid, have large dissociation constants; weak acids, such as acetic acid, have small dissociation constants. The symbol K a , used for the acid dissociation constant, can lead to confusion with the association constant , and it may be necessary to see the reaction or the equilibrium expression to ...
Trifluoroacetic acid (TFA) is a synthetic organofluorine compound with the chemical formula CF 3 CO 2 H. It is a haloacetic acid , with all three of the acetyl group's hydrogen atoms replaced by fluorine atoms.
The higher the proton affinity, the stronger the base and the weaker the conjugate acid in the gas phase.The (reportedly) strongest known base is the ortho-diethynylbenzene dianion (E pa = 1843 kJ/mol), [3] followed by the methanide anion (E pa = 1743 kJ/mol) and the hydride ion (E pa = 1675 kJ/mol), [4] making methane the weakest proton acid [5] in the gas phase, followed by dihydrogen.
The Hammett acidity function (H 0) is a measure of acidity that is used for very concentrated solutions of strong acids, including superacids.It was proposed by the physical organic chemist Louis Plack Hammett [1] [2] and is the best-known acidity function used to extend the measure of Brønsted–Lowry acidity beyond the dilute aqueous solutions for which the pH scale is useful.