Phosphorus solid form

On concentrating the solution, a solid of formula As40jq. SH O (which may be composed by hydrated arsenic(V) acid) is obtained, and this, on fairly prolonged heating to 800 K, loses water and leaves arsenic(V) oxide. No compounds corresponding to the other acids of phosphorus are formed, but salts are known. 

The commonest form of phosphorus, and the one which is usually formed by condensation from the gaseous or liquid states, is the waxy, cubic, white form o -P4 (d 1.8232 gcm at 20°C). This, paradoxically, is also the most volatile and reactive solid form and thermodynamically the least stable. It is the slow phosphorescent oxidation of the vapour above these crystals that gives white phosphorus its most characteristic property. Indeed, the emission of yellow-green light from the oxidation of P4 is one of the earliest recorded examples of chemiluminescence, though the details of the reaction... 

To a flame-dried, three-neck, 1-1 flask were added, in order, p-xylene (107 g, 1.0 mol), phosphorus trichloride (412 g, 3.0 mol), and anhydrous aluminum chloride (160 g, 1.2 mol). The reaction mixture was slowly heated to reflux with stirring. After 2.5 h at reflux, the reaction was allowed to cool to room temperature and the volatile components distilled at reduced pressure. The residual oil was slowly added to cold water (1 1) with stirring, and a white solid formed. The solid was removed by filtration, washed with water, and air dried. The solid was suspended in water (1 1) to which was added 50% sodium hydroxide solution (90 ml) to cause dissolution. The solution was saturated with carbon dioxide and filtered through Celite . The basic solution was washed with methylene chloride (200 ml) and acidified with concentrated hydrochloric acid (200 ml). The white solid that separated was isolated by extraction with methylene chloride (3 x 250 ml). The extracts were dried over magnesium sulfate, filtered, and evaporated under reduced pressure to give the pure 2,5-dimethylbenzenephosphinic acid (99 g, 60%) as an oil, which slowly crystallized to a solid of mp 77-79°C. 

Elemental composition P 37.78%, H 3.69%, 0 58.54%. The acid in solid form may be identified by its physical properties. Aqueous solution may be heated and phosphorus acid is converted to phosphoric acid which is measured for orthophosphate ion by ion chromatography or colorimetry (see Phosphoric Acid). A cold aqueous solution may be analyzed for phosphite ion by ion chromatography, following appropriate dilution. Strength of the acid in an aqueous solution may be measured by acid-base titration using a standard solution of alkali. Also, titration against a standard solution of silver nitrate using potassium chromate as indicator may serve as an additional confirmatory test. 

The flask and contents are placed on a steam cone and heated for 2 hours under vacuum (furnished by a water aspirator) (Note 2) in order to remove the phosphorus oxychloride formed in this process as well as most of the unreacted phosphorus pentachloride. The dry cake is pulverized in a mortar and transferred to a 4-1. beaker. To this is added 750 ml. of distilled water and 2 1. of chloroform. The mixture is placed on a steam bath, heated to boiling, and stirred vigorously until nearly all the solid dissolves. By means of a separatory funnel the layers are separated while still hot. The chloroform solution is again heated to boiling and filtered through a large fluted filter into an Erlenmeyer flask. 

The Mitsunobu phosphonate coupling has been adapted to the solid-phase synthesis of peptidyl phosphonates as well.1 2 In this environment, with excess phosphonate, even the more hindered, p-branched esters are formed efficiently. A series of phosphonate tripeptides have been synthesized and used to identify novel thermolysin inhibitors from a small library. (A number of other solid-phase syntheses of phosphonamidate-, 831 phosphonate-, 79 84 and phosphinate-peptides185,86 have been described however, in these instances the phosphorus bond forming steps were performed in solution, prior to solid-phase coupling.)... 

Substances that are ordinarily deliquescent are sulfuric add (concentrated), glycerol, calcium chloride crystals, sodium hydroxide (solid), and 100% ethyl alcohol. In an enclosed space, these substances deplete the water vapor present to a definite degree. Other substances are used to accomplish this end by chemical reaction, e.g.. phosphorus pentoxide (forming phosphoric acid), and boron trioxide (forming boric acid). Water is absorbed from nonmiscible liquids by addition of such substances as anhydrous sodium sulfate, potassium carbonate, anhydrous calcium chloride. and solid sodium hydroxide. The converse phenomenon is known as efflorescence. 

Phosphorus exists in two common allotropic forms white phosphorus and red phosphorus (Figure 19.9). White phosphorus, the form produced in the industrial synthesis, is a toxic, waxy, white solid that contains discrete tetrahedral P4 molecules. Red phosphorus, by contrast, is essentially nontoxic and has a polymeric structure. 

Phosphorus is nearly the most widely and evenly distributed element on the surface of the earth, and probably the most subdivided. This can be readily understood when the important part which phosphoric acid plays and has played in the vital cosmos is taken into consideration. Phosphorus was on the earth in gaseous, liquid, or solid form before the dawn of life, and since then, all animal and vegetable creations have combined with the physical forces always at work in inanimate nature to distribute and redistribute the phosphorus, to divide it up, and carry it from place to place. If the biography of atoms could be written, the chapters on phosphorus would be the most interesting and the most varied.—W. B. M. Davidson (1893). 

N. Blondlot said that red phosphorus is formed by the action of soln. of potassium, sodium, or ammonium hydroxide on ordinary phosphorus A. Commaille said that with aq. ammonia, some phosphorus hydride is formed—vide infra—and A. Stock and co-workers found that red phosphorus is produced by the aq. ammonia treatment. E. J. Houston considered the phosphorus produced by a protracted heating under potash-lye to be a special modification. B. Lepsius found that red phosphorus is formed when phosphine is decomposed by an electric arc and A. Stock and co-workers, when the solid hydride is heated in vacuo for 24 hrs. at 340°-360°. 

P (c, red). The exact thermodynamic status of the solid forms of phosphorus other than yellow has not yet been determined. The vapor pressure of red phosphorus was measured by Chapman1 and Troost and Hautefeuille1 and the latter calculated, from the difference in the temperature coefficients of the vapor pressures of the yellow and red forms, the heat of transition from yellow to red to be 4.2 at 700°. From the difference in the heats of combustion of the yellow and red forms of phosphorus, Giran1 found T=3.7. A more direct measurement of the heat of transition is that from the data of Giran1 on the heats of reaction of the two forms with bromine in carbon disulfide, (2 = 38.79 and 43.01 for the red and yellow forms, respectively. These data yield T=4.22. Giran1 found that the so-called violet or black phosphorus had a heat of reaction of 38.56 with bromine in carbon disulfide. Apparently this form is thermochemically identical with the red form. 

Allotropic forms of phosphorus. Solid phosphorus exists in two distinct allotropic modifications and is also commonly encountered in a form consisting of a mixture of the two. White (or yellow) phosphorus is a translucent, waxlike solid which melts at 44°C, boils at about 290°C, and has a density of 1.83. When vaporized, the resulting gas consists of tetraatomic molecules (P4) up to a temperature of about 1500°C, whereupon these molecules partly dissociate into (and exist in equilibrium with) diatomic molecules (P2). White phosphorus is insoluble in water but is soluble in solvents such as ethyl ether and carbon disulfide. Great care should always be exercised in handling this form of phosphorus since it is highly flammable and very poisonous. Skin burns caused by phosphorus are exceedingly painful and very slow to heal. 

To a suspension of 39 g (0.163 mol) of l-(2-chloro-2-phenyl-acetyl)-3-ethyl-urea in 250 ml of anhydrous ethyl alcohol is added a sodium ethoxide solution containing 3.75 g (0.163 mol) of sodium dissolved in 250 ml of ethyl alcohol. The mixture is heated under reflux for 2 hours and left overnight at ambient temperature. The precipitated sodium chloride is separated off and copiously washed with alcohol. The alcohol is driven off from the filtrate on the water bath, the oily residue is triturated in 20 ml of iced water, and the solid formed is refrigerated for several hours, separated, washed with water and dried in vacuum over phosphorus pentoxide. The 5-phenyl-2-ethylamino-4-oxazolinone (fenozolone) obtained is recrystallized from anhydrous benzene. It then forms a white crystalline compound soluble in benzene and insoluble in water, MP 148°C. 

An examination of the behaviour of red and violet phosphorus (and indeed all solid forms) in the light of this theory leads to the conclusion that they are mixtures, with the difference that while violet phosphorus is capable of behaving in a unary manner, red phosphorus is not. Violet phosphorus is a mixture, because when it is heated to 360° C. in a vacuum, and the vapour is thus rapidly removed, the vapour pressure falls.2 The inner equilibrium has not in these circumstances time to adjust itself to the loss of the volatile Pa molecules, the residue becomes poorer in this kind and therefore has a lower vapour pressure. The production of red phosphorus below 400° C. may be explained partly by an increase in the proportion of Pa molecules in the solid solution of the pseudo-components, but principally by a delay in the establishment of the equilibrium, which leads to the production of solid solutions still richer in Pa, which are not in equilibrium but which constitute the ordinary red phosphorus. This therefore is not an allotropie modification, if such a modification is defined as a substance which can exist in inner equilibrium and which is able to behave in a unary manner. 

Phosphonium Bromide, PH4Br, was made by Serullas in 1831 from the component gases by direct union.14 Its dissociation pressure reaches only 1 atmosphere slightly below +38° C.13 It can also be made by passing phosphine into the most concentrated aqueous hydro-bromic acid,15 or hydrogen bromide dissolved in phosphoryl chloride,16 or from phosphine and bromine.14 It forms colourless cubic crystals which sublime at about +30° C.17 The heat of formation of the solid from the gases PH3 and HBr is +23 Cals., while that evolved when the initial materials are bromine (liquid), hydrogen and phosphorus (solid) is +44-1 Cals.15... 

Potassium phosphides.-—Phosphine reacts with a solution of potassium in liquefied ammonia to form potassium dihydrophosphide, KH2P, white crystals decomposed by moist air with evolution of phosphine.1 On heating, it is converted into tripotassium phosphide, K3P. A solution of potassium in liquefied ammonia reacts with red phosphorus to form potassium pentaphosphide, KPfi.2 The black product formed from potassium and phosphorus loses its excess of metal in vacuum at 400° to 450° C., yielding dipotassium pentaphosphide, K2P5. It is a lemon-yellow substance with a density of about 2, is unstable in air, and is decomposed by water with formation of solid phosphorus hydride.3... 

Fig. 8. Time evolution of the energy dispersive X-ray powder diffraction of the solid formed when PoOs is used as phosphorus source during the synthesis at 180°C of ULM-5. The intermediate phase is characterized by two peaks at the beginning of the reaction. The (hkl) indices are those of ULM-5.

A suspension of 8-aminoguanine (18.1 mmol) dissolved in 90 ml phosphorus oxychloride and 3 ml 4-dimethylaniline was refluxed 30 minutes and excess phosphorus oxychloride removed. Ice (20 g) was slowly added to the solution, the pH adjusted to 6 with concentrated aqueous NaOH, and a yellow solid formed. The solid was filtered, washed, and... 

Two solid forms of white phosphorus are known, with the cubic a-form converting to the jS-form at 197 K. The basic molecular structure of both consists of the P4 tetrahedron (1). Recent work has raised the intriguing suggestion that liquid phosphorus, consisting of the P4 molecules, undergoes a high-pressure transformation to a polymeric form. Indications are... 

At temperatures attainable in the laboratory we may observe, as has been, said, the exothermic transformation of liquid white phosphorus into the red solid form, but not the inverse transformation the region where the observations are made is, therefore, according to Moutier s rule, to the left of the curve of tensions of transformation from red phosphorus into liquid white phosphorus if the transformation of red into liquid white phosphorus is possible, it is at temperatures much higher than those realizable in our laboratories. 

In modern plants the condensation of phosphorus is carried out in two stages. In a first condensation tower water at 50 to 60°C is sprayed from the top and meets the phosphorus vapor being transported countercurrently from below, whereupon the pho.sphorus condenses as a liquid. The second condensation tower uses water at 10 to 25°C and solid phosphorus is formed. This is periodically melted and as with the first condensation tower run off into a holding tank. The liquid phosphorus is stored under water, drawn off and transported. 

Phosphorus is prepared from the apatites, mineral forms of calcium phosphate, Ca3(P04)2. The rocks are heated in an electric furnace with carbon and sand. The phosphorus vapor formed condenses as white phosphorus, a soft, white, poisonous molecular solid consisting of tetrahedral P4 molecules. It bursts into flame upon exposure to air and is normally stored under water. 

The physical states of reacting substances are important in determining their reactivities. A puddle of liquid gasoline can hum smoothly, hut gasoline vapors can hum explosively Two immiscible liquids may react slowly at their interface, but if they are intimately mixed to provide better contact, the reaction speeds up. White phosphorus and red phosphorus are different solid forms (allotropes) of elemental phosphoms. White phosphorus ignites when exposed to oxygen in the air. By contrast, red phosphorus can be kept in open containers for long periods of time without noticeable reaction. 

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