Allotropes phosphorus

Phosphorus allotropes. Because white phosphorus reacts with air at room temperature, it must be stored under water. Red phosphorus does not react with air at room temperature. 

Black phosphorus allotrope is produced by heating white phosphorus at 220°C under 12,000 atm pressure. The conversion is initially slow, but can became fast and explosive after an induction period. 

Reactivity of white phosphorus is much greater than red or black phosphorus. Black phosphorus is the least reactive of all phosphorus allotropes. 

According to theoretical calculations [114], the most stable modification of a neutral P8 ligands is expected to be the cuneane structure (C), which is found in the phosphorus allotrope known as Hittorff s phosphorus [115,116]. Surprisingly, a ligand conforming to this structural motif has been stabilized in the mixed iron/iridium complex [ Cp Ir(CO) 2(p,q2 2 1 1 1-P8) Cr(CO)5 3] (90), prepared either by photolysis or thermolysis of [Cp Ir(CO)2] with P4 in the presence of excess [Cr(CO)5(thf)] (Scheme 4) [35]. The same unit has also been recognized in the iron derivatives [[CpMeFe(CO) 2(p,q2 2 l l-P8)[CpMeFe(CO)2 2]... 

The white phosphorus allotrope product of the phosphorus furnace is only occasionally used on site. This is because shipping of the most important product, phosphoric acid, involves more than three times the mass of the... 

Two more stable phosphorus allotropes are red and black phosphorus. Small amounts of these are are also produced for special purposes from the white phosphorus product of the electric arc furnace. Red phosphorus is obtained by heating white phosphorus at 400°C for several hours, which yields a complex polymeric material, more dense (2.20 g/cm ) and considerably more stable than the white variety. Red phosphorus is not only stable in air, but far less toxic than white phosphorus. Black phosphorus is more dense again (2.25-2.69g/cm ), and has a different more complex structure. It is obtained by heating the white variety at 220 to 370°C for 8 days plus requires either a pressure exceeding 10 kg/cm or a seed crystal of black phosphorus. This product has a structure resembling graphite, is a good electrical conductor, and can be lit with a match only with difficulty [10] (Table 10.3). 

Vaporized phosphorus is condensed to a white solid (mp = 44.2°C, bp = 280.3°C) under H2O to prevent oxidation. Even when kept under H2O, white phosphorus slowly converts to the more stable red phosphorus allotrope (mp = 597°C sublimes at 431°C). Red phosphorus and tetraphosphorus trisulfide, P4S3, are used in matches. They do not burn spontaneously, yet they ignite easily when heated by friction. Both white and red phosphorus are insoluble in water. 

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