He Hypophosphorous acid , Also known as phosphinic acid, hypophosphite or HPA, is an inorganic compound of formula H 3 PO 2 . It is an oxo acid of phosphorus or hydroxyphosphine oxide, with a monobasic character (PH oxide 3 Which contains an OH-).
It is used for the descriptive presentation of derivatives or salts, whose hydrogen atoms linked to phosphorus are replaced by organic groups, called phosphinates. The term hypophosphite is also used for any salt, ester or anion derived from the name hypophosphorous acid (HYPOPHOSPHOROUS ACID, S.F.).
Figure 1: Structure of hypophosphorous acid.
This compound is formed, together with phosphoric acid and hydrogen phosphide, when phosphorus is boiled in an alkaline or alkaline caustic caustic solution. Hypophosphorous acid is isolated by decomposing its barium salt with sulfuric acid (Wills, 1858).
The barium salt, Ba H 2 PO 2 ) 2 , The free acid can be prepared by double decomposition of a fifth molar solution with the calculated amount of 20 to 25% of sulfuric acid.
The filtered solution can first be evaporated to one tenth of its volume and then until the temperature rises to 105 ° C.
It is filtered hot and then evaporated to a temperature of 110 ° C. This stepwise evaporation is continued until the temperature rises to 130 ° C or even 138 ° C without decomposition.
The liquid is then poured into a closed flask and cooled to 0 ° C, practically solidifying to a mass of crystals. The crystallization can be induced if necessary, by sowing with a crystal of the acid.
Commercial acid usually contains calcium salts. These can be removed by addition of alcohol and much ether to the evaporated solution, when the salts are precipitated. Alcohol and ether are removed by distillation (atomistry.com, 2008-2012).
Physical and chemical properties of hypophosphorous acid
Hypophosphorous acid is a colorless oily liquid or deliquescent crystals (slowly liquefying) with a molecular weight of 66 g / mol.
It has a melting point that varies between 17.4 and 26.5 degrees Celsius. This depends on the amount of water in the acid crystals (National Center for Biotechnology Information, S.F.). The appearance of the compound in the liquid state is shown in figure 2.
Figure 2: appearance of hypophosphorous acid.
The HPA has a density of 1.49 g / ml in the solid state and 1.22 g / ml in 50% w / w aqueous solution. It is soluble in water, alcohol and ether and its formation heat is 137.7 Cal in liquid state and 140.0 Cal in solid state (Royal Society of Chemistry, 2015).
The compound decomposes in phosphoric acid and hydrogen phosphide (phosphine) by heating to temperatures between 130 and 140 degrees Centigrade depending on the reaction:
2H 3 PO 2 → H 3 PO 4 + PH 3
Hypophosphorous acid is a strong reducing agent even stronger than phosphorous acid. It is also possible that it is reduced to phosphine when it encounters a strong reducing agent. Reacts with silver nitrate to give a white precipitate that darkens rapidly, even at low temperatures.
It is oxidized with sulfuric acid, releasing sulfur dioxide and sulfur. May react explosively with mercury (II) oxide and violently with mercury (II) nitrate (Chemical Datasheet HYPOPHOSPHOROUS ACID, 2016).
Reactivity and hazards
Hypophosphorous acid is a corrosive compound for the eyes and skin. The amount of tissue damage will depend on the length of the contact, which may attack the cornea or cause blindness.
Contact with skin may cause swelling and blisters. Inhalation of dust will produce irritation of the gastrointestinal or respiratory tract, characterized by burning, sneezing and coughing. Severe overexposure may result in lung damage, asphyxia, loss of consciousness or death.
Repeated exposure of the eyes to small amounts of dust may cause eye irritation and lead to local skin destruction or dermatitis.
Repeated inhalation of dust may produce a varying degree of respiratory irritation or pulmonary damage (Material Safety Data Sheet Phosphorous acid, 2013). Immediately remove victim to fresh air. If breathing is irregular or stopped, give artificial respiration. Call a physician or Poison Control Center immediately.
In case of skin contact, wash with plenty of water and consult a physician if necessary. In case of contact with clothing, it should be removed immediately and washed with water. It is important not to wear the garments until they are decontaminated.
In case of contact with eyes, rinse thoroughly with water for several minutes. If contact lenses are worn, they should be removed immediately (Special material company, 2015).
Applications
Hypophosphorous acid is used as a reducing agent for electroplating without electrolysis. This product is widely used as reducing agent, Ag, Cu, Ni, Hg and other metals are reduced to the corresponding metal for verification of As, Nb, Ta and other reagents (ChemicalBook, 2016).
It is used as an esterification catalyst. It is also used as a polymerization catalyst and polycondensation.
Hypophosphorous acid is used in medicine in the determination of arsenic, tellurium and separation of tantalum, niobium and other reagents. HPA can be used as a stimulant in pharmaceuticals and as an antioxidant.
It is a strong reducing agent, it can be used for the preparation of sodium hypophosphite, calcium phosphate And other hypophosphites which in turn are used in synthetic fibers as dispersing, emulsifying and antistatic wetting agents
Hypophosphorous acid is used as bleaching or bleaching agent for plastics, synthetic fibers and chemicals.
HPA is used as a bleaching agent and for color stabilization during the manufacture of chemicals and various plastics, including: nylon fibers, polyamides, polyester fiber, polyacrylonitrile, alkyd resins, epoxies, fatty acid esters and glycerols. Company, 2017).
References
- Hypophosphorous Acid, H3PO2. Retrieved from atomistry.com.
- Chemical Datasheet HYPOPHOSPHOROUS ACID. (2016). Retrieved from cameo chemicals.
- (2016). Hypophosphorous acid. Retrieved from chemicalbook.com.
- HYPOPHOSPHOROUS ACID. (S.F.). Retrieved from chemicalland21.
- Material Safety Data Sheet Phosphorous acid. (2013, May 21). Retrieved from sciencelab.com.
- National Center for Biotechnology Information. (S.F.). PubChem Compound Database; CID = 3085127. Retrieved from PubChem.
- Royal Society of Chemistry. (2015). Hypophosphorous acid. Retrieved from ChemSpider.
- Special material company. (2015, February 25). SAFETY DATA SHEET Hypophosphorous Acid. Retrieved from hypophosphorousacid.net.
- Special Materials Company. (2017). Hypophosphorous Acid. Retrieved from hypophosphorousacid.ne.
- Wills, H. (1858). A Handbook of Chemical Analysis:. London: spottiswoode and co.