Phosphates and Thiophosphates, Organic

These materials are combustible. Burning them generates highly toxic fumes of phosphorus oxides and (in the case of the thiophosphates) sulfur oxides. Many fire-retardant foams are organophosphate-based and act to lay down a protective layer that excludes oxygen.

Materials in this group are susceptible to formation of highly toxic and flammable phosphine gas in the presence of strong reducing agents such as hydrides. Partial oxidation by oxidizing agents may result in the release of toxic phosphorus oxides.

Variable. The pyrophosphate esters (such as tetraethyl pyrophosphate) are highly toxic. These derivatives form the basis of a group of insecticides. They interfere with normal nerve transmission by inhibiting cholinesterase. These pesticides should be handled with great care (when released to the environment they are rapidly degraded). Other organophosphates behave similarly.

These compounds are derivatives of phosphoric acid and phosphonic acid in which S may substitute for O and organic groups may substitute for H. They include phospholipids or phosphatides, which are distributed widely in nature in the form of lecithin, certain proteins, and nucleic acids; esters of phosphinic and phosphonic acid, which are used as plasticizers, insecticides, resin ingredients, and flame retardants; pyrophosphates (or diphosphates) which form when phosphate groups condense with the elimination of a molecule of water; phosphate esters of polyols, which are used as components of fertilizer mixtures.

Acephate, chlormephos, chlorfenvinfos, coumaphos, demeton, diazinon, dimefox, dimethoate, ethoprophos, fenamiphos, fonofos, hexaethyl tetraphosphate, isofenphos, isofluorphate, leptophos, merphos, mevinphos, monocrotophos, profenofos, propetamphos.