Saltforming

Saltforming is the process of forming salts by reaction between a salt-forming base (often an amine) and an acid, resulting in ionic compounds that dissociate in solution. In general chemistry, salts result from acid-base reactions.

In organic chemistry, salt formation commonly involves amines (R-NH2) reacting with acids (HCl, H2SO4, organic acids) to give ammonium or other cationic salts, such as amine hydrochloride. The counterion depends on the acid used. The resulting solid salts may be crystalline and have different solubility and stability than the free base or acid.

Salt-forming agents include inorganic acids like hydrochloric acid, sulfuric acid, phosphoric acid; and organic acids like acetic, benzoic, citric acids. Salts may be 1:1 or other stoichiometries; sometimes multi-salt families (dihydrochloride, tartrate, citrate). In pharmacology, salt formation is used to improve solubility, hygroscopicity, dissolution rate, and sometimes bioavailability or taste masking. The choice depends on properties desired and stability profiles across pH.

Methods for creating salts involve screening the base with various acids or the reverse, under controlled conditions; isolation by crystallization or precipitation; and characterization by solid-state and solution-phase analyses. Regulatory considerations for drug products also influence the selection and validation of a particular salt form.