Inorganic acid halides

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In chemistry, functional derivatives of inorganic acids containing oxygen are called inorganic acid halides , which can be derived from the empirical formulas by replacing the hydroxyl group -OH with a halogen atom ( fluorine , chlorine , bromine or iodine ). This classification principle developed from the old term “ acids ” in the early days of chemistry. In more recent textbooks on inorganic and organic chemistry, the term “inorganic acid halides” is rarely used, but it is often used in patent specifications and scientific publications, where it is used to define certain inorganic reactants.

Important examples

From the empirical formula of the sulfur dioxide - H 2 SO 3 - derives the thionyl chloride - SOCl 2 - starting from the sulfuric acid , the sulfuryl chloride SO 2 Cl 2 . Nitryl chloride NO 2 Cl and nitrosyl chloride NOCl are the acid chlorides of nitric acid , HNO 3 and nitrous acid HNO 2, respectively . Phosphorus trichloride and phosphorus tribromide - PX 3 , X = Cl, Br, are related to the phosphorous acid H 3 PO 3 . From orthophosphoric acid H 3 PO 4 this can be phosphorus oxychloride ( phosphoryl chloride ) POCl 3 derived. In deviation from the definition (see above), phosphorus pentachloride PCl 5 is also often counted among the inorganic acid halides; in this case all the oxygen atoms of the phosphoric acid are replaced by halogen atoms. Silicon tetrachloride and boron trichloride can be understood as chlorides of orthosilicic acid H 4 SiO 4 and orthoboric acid H 3 BO 3 , respectively. For the names of some important inorganic acid halides, the radical-functional nomenclature has been used since the beginning of chemistry until today : As the examples show, the name of an acid halide is derived from the corresponding acid radical, e.g. B. Thionyl- (SO-), nitrosyl- (NO-), nitryl- (NO 2 -). However, this nomenclature is not strictly followed: Boron trichloride, silicon tetrachloride, phosphorus trichloride and phosphorus pentachloride are named as halides of the elements.

Reactions

The listed inorganic acid halides react with water in mostly violent reactions to the corresponding acids and hydrogen halides, i. H. Oxonium ions and anions of acids ( hydrolysis ). Inorganic acid halides play an important role in organic synthesis, for example in the conversion of alcohols into alkyl halides and of carboxylic acids into carboxylic acid halides .

literature

  • IUPAC Commission for the Nomenclature of Inorganic Chemistry (Ed.), Rules for the Nomenclature of Inorganic Chemistry, Volume 2. In particular, Group 1, Rule 5.31, page 45, Verlag Chemie, Weinheim, 1976.