In chemistry, a hydrochloride is a salt resulting, or regarded as resulting, from the reaction of hydrochloric acid with an organic base (most commonly an amine). Sometimes chlorhydrate, which is also the French translation. An archaic alternative name is muriate, derived from hydrochloric acid's ancient name: muriatic acid.
For example, reaction of pyridine (C5H5N) with hydrochloric acid (HCl) yields pyridine hydrochloride (C5H5N·HCl). This style of formula is often used for denoting the hydrochlorides although the "dot" incorrectly implies that the two molecules are weakly bonded. The salt C5H5NH+ Cl− is correctly called pyridinium chloride.
Hydrochloric salts are most often referred to by using the name of the base, then simply tagging on hydrochloride or HCl. For example, while crack cocaine is the free base of cocaine, the salt form is often referred to as cocaine HCl.
Converting insoluble amines into hydrochlorides is a common way to make them water-soluble. This characteristic is particularly desirable for substances used in medications. The European Pharmacopoeia lists more than 200 hydrochlorides as active ingredients in medications. These hydrochlorides, compared to free bases, may quickly metabolize in the gastrointestinal tract; the body usually absorbs a hydrochloride within fifteen to thirty minutes. Many hydrochlorides of amines have a longer shelf-life than their respective free bases.
- P. Heinrich Stahl (Editor), Camille G. Wermuth (Editor): Pharmaceutical Salts: Properties, Selection, and Use, 2. Ed., Wiley, 2011, ISBN 978-3-90639-051-2.
- European Pharmacopoeia 7th Edition 2011, EDQM.