Organophosphorus

Organophosphorus compounds are a broad class of chemicals that contain phosphorus atoms bonded to carbon or to oxygen or sulfur atoms, often with phosphorus-oxygen double bonds. They include organophosphates, organophosphonates, and related derivatives. Many have biological activity and are studied in chemistry, agriculture, toxicology, and materials science. The term covers a range of substances from insecticidal esters to nerve agents, as well as naturally occurring phosphorothioates found in some organisms.

In terms of structure, organophosphorus compounds typically feature phosphorus in a high-oxidation state with one or more alkoxy or aryloxy substituents and varying ligands such as halides or thio substituents. Organophosphates are often esters of phosphoric or phosphorothioic acids, whereas organophosphonates contain a phosphorus-carbon bond (P–C). This diversity leads to a wide range of physical properties and reactivities, from volatile liquids to solid polymers or flame retardants.

Applications and examples vary widely. Many organophosphates are used as pesticides, including compounds historically employed in agriculture. Organophosphorus esters have also been developed as flame retardants and plasticizers. Some organophosphorus compounds have been investigated or developed as chemical warfare agents, such as nerve agents, though such materials are tightly controlled under international law. Conversely, several organophosphorus compounds are important in medicinal chemistry and biochemistry as enzyme inhibitors or probes.

Toxicology and safety are central concerns. Organophosphorus compounds often inhibit acetylcholinesterase, leading to accumulation of acetylcholine and overstimulation of cholinergic receptors. Acute exposure can be life-threatening; management relies on supportive care and antidotes such as atropine and oximes. Regulation and handling guidelines reflect the significant hazards associated with many members of this class.