Phosphorodifluoridic acid

Phosphorodifluoridic acid, HPO2F2, mp = -96°C, bp = 116°C, can be prepared by a direct reaction between phosphoromonofluoridic acid and phosphoryl fluoride under anhydrous conditions (5.272). It is toxic, corrosive and an irritant. It is a clear mobile liquid which decomposes at 100°C, fumes in the atmosphere and hydrolyses slowly in water to form phosphoromonofluoridic acid. It is a strong 

H2PO3F + POF3 - 2HPO2F2 HPO2F2 + PBrj POF2Br + POBr3 + HBr 

Phosphorofluoridates are obtained by heating hexafluorophosphates with metaphosphates (5.274) or boric oxide (5.275). A recent preparation of the potassium salt utilises the reaction between KH2PO4, aqueous HF and acetic anhydride (5.276) [27]. 

Phosphoromonofluoridic acid, H2PO3F, is a colourless oil somewhat like concentrated sulphuric acid in appearance. It is an acid of moderate strength (Table 5.21), which is only slowly hydrolysed in mildly alkaline or neutral solution. In concentrated acid or alkaline solution, this hydrolysis is more rapid. The anhydrous acid does not attack glass but with alkaline borohydrides, borane is obtained (Chapter 9.1). 

Phosphoromonofluoridates in solution will give a precipitate with silver nitrate (5.277). The sodium and stannous salts (5.278) are used in toothpaste formulations to inhibit dental caries. They act by converting the tooth hydroxyapatite into the somewhat harder and more acid-resistant fluor- 

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F2H02P, Phosphorodifluoridic acid rhenium complex, 26 83 F2N2OsPReCijH , Rhenium (2,2 -bipyri-dine)-tricarbonyl(phosphoro-difluoridato)-, 26 83... 

NIOSH REL TWA 2.5 mg(F)/m3 DOT CLASSIFICATION 8 Label Corrosive SAFETY PROFILE Toxic and corrosive material. Very irritating to the skin, eyes, and mucous membranes. When heated to decomposition it emits very toxic fumes of POx and F". Used as a catalyst. See also PHOSPHORODIFLUORIDIC ACID, anhydrous. 

PHOSPHORODIFLUORIDIC ACID see PHF250 PHOSPHORODI(ISOPROPYLAMIDIC) FLUORIDE see PHF750... 

The diphosphoric tetrafluoride for this synthesis is best prepared18 by reaction of phosphorodifluoridic acid with an excess of phosphorus ) oxide. Extremely pure P203F4 is not required. It contains about 5 % of the starting material. The same procedure, but using 18.6 g. (0.1 mole) of diphosphoric tetrafluoride instead of the acid in the method given above, may be utilized to prepare POF2Cl. The purification step described above is not necessary in this synthesis.12 The yield is 23 g. (95 %). 

Phosphorodifluoridic acid (difluorophosphoric acid) (51 g., 0.5 mole) and 258 g. (0.6 mole) of phosphorus pentabromide are placed in a two-necked 500-ml. flask equipped with a distillation head and a mechanical stirrer. The reaction flask is heated in an oil bath within 2 hours to 90-95°, and heating is continued for another 2 hours at 95-105°. The resulting volatile liquid is distilled during... 

PHOSPHORODIFLUORIDIC ACID or PHOSPHORODIFLUORIDIC ACID (ANHYDROUS) (13779-41-4) Reacts with moisture in air, forming hydrogen fluoride. Reacts with water, steam, forming hydrofluoric acid. Aqueous solution incompatible with sulfuric acid, alkalis, ammonia, aliphatic amines, alkanolamines, alkylene oxides, amides, epichlorohydrin, organic anhydrides, isocyanates, vinyl acetate. Attacks glass and other siliceous materials. Attacks metals in the presence of moisture. 

HClZrC oH, ), Zirconium, chlorobis(Ti -cyclopentadienyl)hydrido-, 28 259 HF2O2P, Phosphorodifluoridic acid, rhenium complex, 26 83 HFj04P2PtSC 4H34, Platinum(II), hydrido-(methanol)bis(triethylphosphine)-, trans-, trifluoromethanesulfonate, 26 135... 

Precautions Could be corrosive to skin or eyes. An irritant. Synonyms phosphorodifluoridic acid... 

Phosphorofluoridic acid (monofluorophosphoric acid) and phosphorodifluoridic acid (difluorophos-phoric acid) are produced in the intermediate stages of hydrolysis of phosphoryl fluoride, and can be isolated under suitable conditions. 

FN203ReC 3H , Rhenium, (2,2 -bipyridine)-tricarbonylfluoro-, 26 82 FO,S,C, H 2,2 -Bi-l,3-dithiolo[4,5-6]-[l,4]dithiinylidene fluorosulfate, 26 393 F2HO2P, Phosphorodifluoridic acid rhenium complex, 26 83 F2N20sPReCi3H, Rhenium (2,2 -bipyri-dine)-tricarbonyl(phosphoro-difluoridato)-, 26 83... 

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