Hydrides of phosphorus

Optional experiment. When all the air has been displaced, collect a test-tube of the gas over water (by appropriate inclination of the end of the delivery tube beneath the mouth of a test-tube filled with water and supported in a beaker of water). Observe the colour and odour of the gas. Ignite the test-tube of gas, and note the luminosity of the flame and the amount of carbon deposited. Pure acetylene is almost odourless the characteristic odour observed is due to traces of hydrides of phosphorus, arsenic and sulphur. 

The temperature must be raised slowly to avoid formation of spontaneously inflammable hydrides of phosphorus whict will ignite and destroy the preparation. A similar result occur if the phosphorus tribromide is added at 170°. 

Predict the formula and molecular shape of a hydride of phosphorus. 

However, PH3 is not the only hydride of phosphorus, and it is not the only product of this reaction. The other hydride of phosphorus is diphosphine, P2H4, which is produced in the reaction just shown. This compound is spontaneously flammable in air, and it ignites phosphine, which is also flammable. 

Toxicity Variable. The hydrides of phosphorus, arsenic, sulfur, selenium, tellurium and boron which are highly toxic, produce local irritation and destroy red blood cells. They are particularly dangerous because of their volatility and ease of entry into the body. The hydrides of the alkali metals, alkaline earths, aluminum, zirconium and titanium react with moisture to evolve hydrogen and leave behind the hydroxide of the metallic element. This hydroxide is usually caustic. See also sodium hydroxide... 

The hydrides of phosphorus, arsenic, and antimony thus form an interesting transition series. On similar sorts of surface antimony hydride is the least stable, decomposing with measurable speed at ordinary temperatures, and phosphine is the most stable, not decomposing at an appreciable rate below a red heat. Arsine occupies an intermediate position. At low temperatures the adsorption is considerable, and, as a result, the stibine decomposition requires the pn equation, while the more stable hydrides, which only decompose rapidly at higher temperatures where the adsorption is smaller, obey the unimolecular law. It is interesting, moreover, that with stibine itself the exponent n increases towards unity as the temperature at which the reaction takes place is raised. 

Phosphine Phosphine (PH3), a colorless, extremely poisonous gas, is the most important hydride of phosphorus. Like NH3, phosphine has a trigonal pyramidal structure and has the group 5A atom in the —3 oxidation state. Unlike NH3, however, its aqueous solutions are neutral, indicating that PH3 is a poor proton acceptor. In accord with the low electronegativity of phosphorus, phosphine is easily oxidized, burning in air to form phosphoric acid ... 

The first two examples in Figure 1.20 illustrate that the structural formulas of alkyl and aromatic phosphine compounds may be derived by substituting organic groups for the H atoms in phosphine (PH3), the hydride of phosphorus, discussed as a toxic inorganic compound in Section 12.10. Methylphosphine is a colorless, reactive gas. Crystalline, solid triphenylphosphine has a low reactivity and moderate toxicity when inhaled or ingested. 

The principal hydride of phosphorus is phosphine, PH3 (with struc-... 

The most important hydride of phosphorus is phosphine, PH3, a colorless, very poisonous gas formed by heating white phosphorus in concentrated sodium hydroxide ... 

The simplest hydrides of phosphorus and boron incorporating 3- and 4-coordinated atoms are... 

The hydrides of phosphorus are called phosphines. The general formula for this homologous series of very poor thermal stability is P H +2 ( = 1-6). Other, even less stable homologous series are also known. 

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