Diisopropyl fluorophosphate (DFP, DIFP, diisopropyl phosphorofluoridate) is an oily, colorless liquid with the chemical formula C6H14FO3P. It is used in medicine and as an organophosphorusinsecticide. It is stable, but undergoes hydrolysis when subjected to moisture, producing hydrofluoric acid. It is known also under names Difluorophate, Diflupyl, Diflurphate, Dyflos, Dyphlos, Fluropryl, Fluostigmine, isofluorophate, isofluorphate, Neoglaucit, PF-3, PF3, T-1703, TL 466, and others.
The marked toxicity of esters of monofluorophosphoric acid was discovered in 1932, when Willy Lange and his PhD student Gerda von Krueger prepared the methyl, ethyl, n-propyl, and n-butyl esters and incidentally experienced their toxic effects. Another homologue of this series of esters, Diisopropyl fluorophosphate, was developed by British scientist Bernard Charles Saunders. On his search for compounds to be used as chemical warfare agents, Saunders was inspired by the report by Lange and Krueger and decided to prepare the new homologue which he labeled PF-3. It was much less effective as a chemical weapon than the G series agents. It was often mixed with mustard gas, forming a more effective mixture with significantly lower melting point, resulting in an agent suitable for use in cold weather.
Crystal structure of Herpes Simplex Virus Protease/Inhibitor (DFP) complex. The active site serine (yellow) has undergone phosphonylation resulting in irreversible inhibition. Rendered from PDB 1AT3.
In military research, due to its physical and chemical similarities and comparatively low toxicity, it is used as a simulant of G-agents (GA, GB, GD, and GF).
Diisopropyl fluorophosphate is a very potent neurotoxin. Its LD50 in rats is 1.3 mg/kg. It combines with the amino acidserine at the active site of the enzyme acetylcholinesterase, an enzyme that deactivates the neurotransmitteracetylcholine. Neurotransmitters are needed to continue the passage of nerve impulses from one neuron to another across the synapse. Once the impulse has been transmitted, acetylcholinesterase functions to deactivate the acetylcholine almost immediately by breaking it down. If the enzyme is inhibited, acetylcholine accumulates and nerve impulses cannot be stopped, causing prolonged muscle contraction. Paralysis occurs and death may result since the respiratory muscles are affected.
DFP also inhibits some proteases. It is a useful additive for protein or cell isolation procedure.
Isoflurophate, the di-iso-propyl ester of fluorophosphoric acid, is made by reacting isopropyl alcohol with phosphorus trichloride, forming di-iso-propylphosphite, which is chlorinated and further reacted with sodium fluoride to replace the chlorine atom with fluorine, thus giving isofluorophate.