Phosphite

Phosphite refers to compounds containing phosphorus in the +3 oxidation state that are derived from the phosphorous acid system, including both inorganic and organic derivatives. In common usage the term describes the inorganic phosphite ion PO3^3− and its salts, as well as phosphite esters, which are organic derivatives of phosphorous acid.

Inorganic phosphites and salts consist of the phosphite ion PO3^3− and corresponding salts such as sodium phosphite and potassium phosphite. In aqueous solution these species behave as weak bases and are readily oxidized by air to phosphate. They are used as reducing agents, corrosion inhibitors, and in some cases as stabilizers for metal surfaces.

Phosphite esters are organic derivatives of phosphorous acid in which the hydroxyl groups are replaced by alkoxy or aryl groups. The simplest example is triethyl phosphite (P(OEt)3). Phosphite esters are widely used in organic synthesis as reagents and ligands, and they find applications as intermediates, in polymer formulations, and as additives in various industrial processes.

Applications and context: Phosphite salts are used in agriculture as fungicides to control oomycete pathogens such as Phytophthora. They can have systemic activity in some plants, but they are not considered true phosphate fertilizers. Phosphite esters, by contrast, are primarily academic and industrial reagents, playing roles in synthesis, catalysis, and materials science.

Safety and environment: Phosphite compounds should be handled with appropriate precautions, including personal protective equipment and proper storage. They can pose health and environmental risks if misused or released in significant quantities; follow label instructions and regulatory guidelines for handling, use, and disposal.