Phosphite di-isopropyl hydrogen

The following preparation of triethyl phosphite illustrates the interaction of phosphorus trichloride and ethanol in the presence of dimethylaniline the preparation of di-isopropyl hydrogen phosphite illustrates that of phosphorus trichloride and isopropanol in the absence of a tertiary amine. 

Meanwhile set up the ether distillation apparatus as used in the preparation of triethyl phosphite (p. 308). Distil off the ether and then fractionally distil the residue at water-pump pressure. The di-isopropyl hydrogen phosphite distils at 79Vi4 mm. other b.ps. are 8o°/i5 mm., 82-5°/i7 mm. Yield, 25 g., 89%. 

Di-isopropyl hydrogen phosphite is a colourless mobile liquid, which, unlike triethyl and tri-isopropyl phosphite, is completely miscible with water, due undoubtedly to the polar P=0 group. 

B) The following simpler preparation of di-isopropyl hydrogen phosphite using the same quantities of reactants requires no solvent or ammonia, but gives a lower yield. 

Di-isopropyl phosphoroehloridate.3 Di-isopropyl hydrogen phosphite (0-1 mol.) is dissolved in dry carbon tetrachloride, and to the solution Y-chlorosuccinimide (0-1 mol.) is added in portions of 0-5 g., with shaking and occasional cooling. After the addition, the solution is cooled to — 5° and the precipitated succinimide filtered off. Carbon tetrachloride is removed from the filtrate by warming under reduced pressure, and the residual liquid is fractionated. Practically the whole of it boils at 94-95°/14 mm. Yield 17-5 g., 82 per cent. 

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

Further modifications were then made in this hydrogen phosphite method of preparing di-isopropyl phosphorofluoridate in order to put it on an industrial scale. 

We found that the toxicity and myotic activity of di-isopropyl phosphorofluoridate (XI) were far greater than that of di- propyl phosphorofluoridate. In Report no. 6 on fluoro-phosphonates to the Ministry of Supply3 we described the preparation of di aec.-butyl phosphorofluoridate (XII) by the hydrogen phosphite method (p. 6). The compound was found to be very toxic and to produce severe myosis in man and animals. The symptoms displayed during and after exposure were identical with those produced by di-isopropyl phosphorofluoridate. The L.c. 50 for di-sec.-butyl phosphorofluoridate for mice for deaths within 2 hr. was 0-6 mg./l., and that for deaths within 48 hr. was 0-54 mg./l. 

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