Phosphorus oxydichlorofluoride

It should be emphasized that the phosphorus oxydichlorofluoride method for preparing esters of phosphorofluoridic acid cannot compare in speed with the hydrogen phosphite method already described (p. 46). Furthermore, it is not very suitable for very large-scale work. On the other hand, once the apparatus is set up and a supply of POClj is obtained, one has a simple, clear-cut, method for producing a large variety of phosphorus compounds, not only esters but amino compounds (p. 87) and mixed compounds (p. 90). In other words, the method is extremely valuable for exploratory purposes and where an unequivocal synthesis is required. 

Apparatus. The generator employed is shown in fig. 10. There are six important points. (1) The column. 4 is designed so that throttling is avoided it is at least 2 ft. long and surmounted by a reflux doublesurface water-condenser B. (2) A Perkin triangle (air-cooled), inserted between the down-condenser and the traps, enables any phosphorus oxychloride which distils to be removed. (3) It is convenient to have three traps, viz. C, ice and salt D, acetone and carbon dioxide E, liquid air. (4) The intermittent addition of the solid antimony trifluoride presents a problem. The mechanical sohd feed 

Procedure. Finely powdered antimony trifluoride is placed in the reservoir of the feed. Phosphorus oxychloride and then antimony pentachloride are placed in the reaction vessel. The temperatmre of the bath is maintained, thermostatically, at 75° and the pressine kept at 190-200 mm., and the antimony trifluoride is then added slowly from the feed. The distillates in the traps are united and fractionated. The distillate, up to b.p. 90°/760 mm., is collected and carefully refractionated, giving pure phosphorus oxydichlorofluoride, b.p. 54° (20 per cent yield). 

Di-iaopropyl phosphorofluoridate. Phosphorus oxydichlorofluoride (50 g.) is dissolved in dry ether (100 c.c.), tsopropyl alcohol (dried over calcium oxide 50 g., 15 per cent excess) in dry ether (100 c.c.) is added slowly with cooling, and the mixture kept for 1 hr. Dry ammonia is then passed through the liquid, with cooling. The liquid 

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Di 2 fluoroethyl phosphorofluoridate (XVIII) was prepared with the idea of combining the toxic principles of the fluoro-aoetates and of the phosphorofluoridates. It was readily obtained by the action of phosphorus oxydichlorofluoride on... 

Preparation of Esters of Phosphorofluoridic Acid by means of Phosphorus Oxydichlorofluoride... 

In a Report to the Ministry of Supply (27 February 1942) we proposed a method for synthesizing esters of phosphorofluoridie acid by the reaction between phosphorus oxydichlorofluoride and the appropriate alcohol ... 

The reaction depended upon the marked difference in reactivity between the chlorine atoms and the fluorine atom in phosphorus oxydichlorofluoride. In general, the reaction with alcohols waa clear-cut, and most of the phosphorofluoridic esters were obtained in excellent yield and uncontaminated with the phosphoric triester. For example, when ethyl alcohol and phosphorus oxydichlorofluoride were allowed to react in the odd, diethyl phosphorofluoridate (VII, R = Et) was obtained in 93 per cent yield. No tertiary base was necessary to remove the hydrogen chloride produced in the reaction. The general process was patented during the war.1... 

The method depended upon the availability of phosphorus oxydichlorofluoride, a compound described by Booth and Dutton,2 who devised an elaborate apparatus for the preparation of the compound in a pure condition for physicochemical measurements. We modified their process to suit the particular needs of this work. The generator which we developed for this step-... 

In order to determine whether other secondary alcohols would give phosphorofluoridic esters of high potency, dicycio-hexyl phosphorofluoridate (VIII) was prepared by the action of phosphorus oxydichlorofluoride on cyciohexanol. In this preparation it was essential to remove all the hydrogen chloride before distillation, otherwise decomposition took place. The... 

Diphenyl phosphorofluoridate was prepared in 60 per cent yield by the action of phosphorus oxydichlorofluoride on phenol in the presence of dimethylaniline to take up the hydrogen chloride formed. Gottlieb3 claimed to have prepared this... 

As we have seen (pp. 50 et seq.) the reaction between phosphorus oxydichlorofluoride and alcohols, phenols and thiols, affords dialkyl, dicyctoalkyl, diaryl phosphorofluoridates and dialkyl phosphorodithiolates. In a Report1 to the Ministry of Supply on fluorophosphonates a description was given of a new type of nitrogen fluorophosphonate formed by the action of 4 mol. of aniline on 1 mol. of phosphorus oxydichlorofluoride, the fluorine atom being unaffected ... 

Later, American workers2 described the preparation of this type of compound by a method which necessitated the loss of two-thirds of the fluorine concerned in the reaction. They prepared tetramethylphosphorodiamidic fluoride (bisdimethyl-aminofluorophosphine oxide) (II) by the action of phosphorus oxyfluoride on the calculated quantity of dimethylamine. In addition, it should be emphasized that phosphorus oxyfluoride is a gas and is more difficult than the liquid phosphorus oxydichlorofluoride to manipulate. In Report no. 14 on fluoro-phosphonates to the Ministry of Supply3 it was shown that our reaction could also be applied to the preparation of tetramethyl-... 

A distinctly different method of synthesizing the esters of phosphorofluoridic acid consisted in the partial fluorination of phosphorus oxychloride with antimony trifluoride (using a specially designed apparatus and phosphorus pentachloride as catalyst) to give phosphorus oxydichlorofluoride, POClaF. In the latter compound the chlorine atoms proved to be much more reactive than the fluorine atom, and with an alcohol the dialkyl phosphorofluoridate was readily obtained in high yield. ... 

Although the action of POClaF on an alcohol cannot compete with the hydrogen phosphite method for large-scale work, the (vmer was found extremely valuable for exploratory purposes. In particular, it was found possible to prepare diaryl phosphoro-fluoridates (e.g. (C,H50)aPOF) and diethyl phosphorofluorido-dithiolate (diethyl dithiofluorophosphonate, (CaH5S)aPOF) by the action of phosphorus oxydichlorofluoride on the appropriate phenol or mercaptan. 

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