Phosphorus molecular oxides

Phosphorus(III) oxide dissolves in several organic solvents, for example benzene, carbon disulphide the molecular weight in these solvents corresponds to the formula P40(, as does the density of the vapour, and the structure is ... 

Formula P2O5 MW 141.95 exists as P4O10 units as molecular entities Synonyms phosphorus pentaoxide phosphorus(V) oxide phosphoric anhydride... 

Roman numeral, as though phosphorus were a metal and the oxide present as O2-. Thus, P406 is thought of as (P1+)4(02 )6 and named phos-phorus(III) oxide, and P4O10 is thought of as (P5+)4(O2 )10 and named phosphorus(V) oxide. These compounds, though, are molecular. 

Solvents are rigorously dried by repeated distillation in vacuo from phosphorus-(V) oxide. The alkyl nitriles are generally predried by refluxing them over calcium hydride for several days, then distilling several times from phosphorus (V) oxide, and finally from potassium carbonate the liquid is then stored either over phosphorus (V) oxide on the vacuum line or in contact with molecular sieves in the dry-box. 

Although crystals of the /3-phase of phosphorus(IIW) oxides with a high content of P4Og can be obtained (7, 71, 72, 73),3 nobody has yet been able to isolate the pure oxide. D. Heinz et al. assumed that phospho-rus(IIW) oxide mixtures that contain >95% of P408 form only amorphous solids. This may be due to the fact that P408 has the lowest molecular symmetry of all phosphorus oxides considered here. Further investigation of this subject is still in progress. 

By the end of the nineteenth century, molecular weight determinations carried out by means of vapor density measurements proved that phosphorus(V) and phosphorus(III) oxide in the gaseous state consist of molecules of the compositions P406 (3,86) and P4O10 (87), respectively. However, their molecular structures remained uncertain (see, for example, Ref. 88) until adequate techniques for structure determination such as electron and X-ray diffraction became available (6, 7, 72). 

Concerning the phosphorus(III/V) oxides, no structural data in the gaseous state are available the only attempt (89) to determine the molecular structure of one of the phosphorus(IIW) oxides, P408, has failed. 

The synthetic approaches to molecular phosphorus(IIW) oxides and oxide sulfides have some features in common The compounds P4O6X (X = O, S) are prepared from the lowest oxidized member of the P40eX series (P4O6 itselD by the reactions... 

Phosphorus(III) oxide, P4O6, is obtained by burning white phosphorus in a restricted supply of O2. It is a colourless, volatile solid (mp 297 K, bp 447 K) with molecular structure 14.56 the P—O bond distances (165 pm) are consistent with single bonds, and the angles P—O—P and O—P—O are 128° and 99° respectively. The oxide is soluble in diethyl ether or benzene, but reacts with cold water (equation 14.118). 

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