Гипофосфорнокислый

Description

Hypophosphorous acid (hypophosphorous acid, HYPOPHOSPHOROUS ACID) is an oxoacid of phosphorus, a strong reducing agent with the molecular formula H3PO2. The free acid is called by this name in inorganic chemistry, although the systematic IUPAC name is dihydridohydroxydophosphorus, an acceptable alternative name is phosphinic acid. The formula is often written as H3PO2, but the more descriptive spelling HOP(O)H2 emphasizes the monoprotic nature of the acid: only one hydrogen atom out of three is capable of dissociation. Salts obtained from this acid are called phosphinates (hypophosphites). English name Hypophosphorous acid, CAS number 6303-21-5, EC number 228-601-5, DSSTox identifier DTXSID70162386, HS code 28111990. The substance is included in the TSCA list. According to the classification, ChEBI refers to phosphorus oxoacids, in which the pentavalent phosphorus atom is covalently linked by single bonds to two hydrogen atoms and a hydroxyl group and a double bond to oxygen; is the founder of the class of phosphinic acids.

Physico-chemical characteristics

• Color/shape: colorless
• Appearance: colorless liquid
• Molecular mass: 63.980501 (according to one source), exact mass 66.00
• Physical properties: colorless crystals that diffuse in air or an oily liquid with a sour odor; highly soluble in water, alcohol and ether
• Density: 1.493 g/cm3 (general physical properties); 1.206 g/ml at 20 °C (lit.); density of 50% aqueous solution 1.13 g/ml
• Melting point: 26.5 °C (based on physical properties); -25 °C (according to some literature data)
• Boiling point: 130 °C (based on general physical properties)

Substance class and features

The acid is formed together with phosphorus and phosphoric acid during the oxidation of phosphorus with moist air. When white phosphorus is exposed to air and sodium acetate is added to the resulting liquid, a slightly soluble precipitate of sodium hypophosphate Na2H2P2O6 6H2O precipitates; sodium hypophosphate monohydrate, on the contrary, is highly soluble and separates at a concentration of about 98.7 g per 100 ml of solution.

Application

The main industrial application is chemical (electrolysis-free) nickel plating as a reducing agent in the deposition bath of nickel-phosphorus coatings with increased hardness, wear resistance and corrosion resistance for the electronics and automotive industries; For this purpose, its salt, sodium hypophosphite, is most often used. The acid and its salts are used as a brightening agent and color stabilizer in the production of nylon fibers, polyamides, polyester fibers, polyacrylonitrile, alkyd resins, epoxies, fatty acid esters and glycerols. In organic synthesis it is used for the reduction of diazonium salts at the stage of removing amino groups from aromatic compounds; Sodium hypophosphite is considered an accessible, inexpensive and environmentally friendly reagent in organophosphorus synthesis. Products of the acid-based phospha-Mannich reaction—(α-aminoalkyl)phosphine compounds—are used as flame retardants and chelators of di- and trivalent metals, including in metal-containing radiopharmaceuticals for diagnostics and therapy.

Storage conditions

Store in a tightly closed container in a cool, dry place, away from incompatible materials; the substance diffuses in air and must be protected from moisture.