Hypophosphorous acid
[CAS# 6303-21-5]

Identification

• Classification: Inorganic chemical industry >> Inorganic acid
• Name: Hypophosphorous acid
• Synonyms: Phosphinic acid
• Molecular Formula: H₃PO₂
• Molecular Weight: 66.00
• CAS Registry Number: 6303-21-5
• EC Number: 228-601-5
• SMILES: O[PH2]=O

Properties

• Density: 1.274
• Water solubility: SOLUBLE

Safety Data

• Hazard Symbols: GHS05 Danger
• Risk Statements: H290-H314
• Safety Statements: P234-P280-P303+P361+P353-P304+P340+P310-P305+P351+P338-P363

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin corrosion	Skin Corr.	1B	H314
Serious eye damage	Eye Dam.	1	H318
Substances or mixtures corrosive to metals	Met. Corr.	1	H290
Skin corrosion	Skin Corr.	1A	H314
Skin corrosion	Skin Corr.	1	H314

• Transport Information: UN 1760; UN 3264

Discovery and Applications

Hypophosphorous acid, also known as phosphinic acid, is an inorganic compound with the formula H₃PO₂. This colorless, odorless acid is characterized by its unique structure, containing one phosphorus atom bonded to two oxygen atoms and one hydrogen atom, with the other valence occupied by a hydroxyl group. The discovery of hypophosphorous acid dates back to the early 19th century, when it was first synthesized by the German chemist H.J. Kolbe in 1840. The compound was initially produced by the reduction of phosphoric acid with zinc or other reducing agents, leading to its recognition as a distinct chemical entity.

The applications of hypophosphorous acid have expanded over time, finding utility in various fields including organic synthesis, electroplating, and the production of specialty chemicals. In organic chemistry, hypophosphorous acid serves as a reducing agent, effectively converting various functional groups, such as ketones and aldehydes, into their corresponding alcohols. Its mild reducing properties make it a valuable tool in synthetic pathways, allowing for selective reductions without the harsh conditions often required by stronger reducing agents.

In the realm of electroplating, hypophosphorous acid is utilized as a source of phosphorus in the deposition of nickel-phosphorus alloys. These alloys exhibit excellent wear resistance and corrosion resistance, making them ideal for applications in the automotive and aerospace industries. The ability to control the phosphorus content in the deposited alloy allows for the tailoring of properties, enhancing the performance of the coated surfaces.

Moreover, hypophosphorous acid has been explored for its potential applications in the field of medicine. It has shown promise as a reducing agent in the synthesis of various pharmaceutical compounds, as well as a possible antioxidant. Research is ongoing to better understand its biological activities and potential therapeutic effects.

In addition to its industrial applications, hypophosphorous acid is also employed in the synthesis of phosphorus-containing flame retardants. These compounds are crucial for enhancing the fire resistance of various materials, including plastics and textiles, thus contributing to safety in consumer products.

The continued research and development surrounding hypophosphorous acid highlight its versatility and importance in both industrial and scientific applications. As advancements in chemistry evolve, the potential uses of this compound are likely to expand further, cementing its role as a valuable substance in various domains.

References

2007. Emergency Care For Hazardous Materials Exposure, 3rd revised edition. Elsevier Mosby, St. Louis, MO, p. 490.

2007. Emergency Care For Hazardous Materials Exposure, 3rd revised edition. Elsevier Mosby, St. Louis, MO, p. 491.

2012. Reduction with Phosphinic Acid and Its Derivatives. Science of Synthesis.
Available from: https://science-of-synthesis.thieme.com/app/text/?id=SD-206-00494

2017. Sodium Phosphinate (7681-53-0) Registered Substances Dossier. European Chemical Agency.
Available from: https://echa.europa.eu/