HO2PO2H

HO2PO2H, also known as hypophosphorous acid, is a chemical compound with the formula H3PO2. It is a strong reducing agent and is considered to be one of the oxyacids of phosphorus. In its pure form, hypophosphorous acid is a colorless, odorless liquid, but it is often encountered as an aqueous solution. The compound is characterized by the presence of a phosphorus atom bonded to one hydroxyl group (OH) and two hydrogen atoms, with the remaining valence satisfied by a double bond to an oxygen atom. This structure is distinct from other phosphorus oxyacids like phosphoric acid (H3PO4) or phosphorous acid (H3PO3).

Hypophosphorous acid is a strong acid, readily donating its proton. Its reducing properties are significant, making it useful in various chemical applications. It can reduce metal ions to their elemental form and is employed in electroplating processes, particularly for nickel plating, to deposit a layer of nickel on surfaces. It also finds use as a chemical reducing agent in organic synthesis and as a stabilizer in certain polymers.

The compound is typically prepared by the reaction of white phosphorus with a strong base, followed by acidification. Alternatively, it can be synthesized through the hydrolysis of phosphorus trihalides. While hypophosphorous acid itself is not particularly toxic, its salts, known as hypophosphites, can have varying degrees of toxicity. Care should be taken when handling this strong acid due to its corrosive nature.