Phosphorochloridate di-isopropyl

Di-isopropyl phosphorofluoridate is a practically odourless, mobile liquid, b.p. 183°/760 mm. (by extrapolation), f.p. ca. -82°. This wide range of temperature over which the compound is liquid adds to its usefulness. A specimen of the pure liquid has remained unchanged in a glass vessel for several years. Whereas the phosphorochloridate was readily hydrolysed by water, hydrolysis of the phosphorofluoridate was slow and took 72 hr. for completion at 15° and then only in the presence of a large excess of water (1 per cent solution solubility 1-5 per cent) P(OPr<)2 of+hso - P(OPrf)2 oh + hf. 

Dimethyl and diethyl phosphorofluoridate were hydrolysed much more quickly, the order being Me>Et>Pr complete hydrolysis of the ethyl ester took about 4 hr. Small quantities of the di-isopropyl, but not the diethyl ester, could be steam-distilled. Bi-isopropyl phosphorochloridate can be readily identified by allowing it to react with aniline to give the crystalline phenylphosphoramidate ... 

The active trichloride was converted into di-isopropyl hydrogen phosphite and thence through the phosphorochloridate into the phosphorofluoridate essentially according to the scheme... 

The ester must in addition contain some group which will initiate the approach of the ester to the surface of the enzyme. In this connexion it should be noted that di-isopropyl phos-phorochloridate (III, X = Cl), in which the chlorine atom is chemically very reactive,3 has no toxic properties, is devoid of myotic and anti-cholinesterase activity. In this compound, the chlorine is hydrolysed very quickly in water and would probably be destroyed extremely quickly in vivo. We have shown, quite conclusively, that in non-polar solvents the phosphorochloridate... 

---