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Phosphorus pentoxide crystallizes in at least four forms or polymorphs.The most familiar one, a metastable form [1] (shown in the figure), comprises molecules of P 4 O 10.Weak van der Waals forces hold these molecules together in a hexagonal lattice (However, in spite of the high symmetry of the molecules, the crystal packing is not a close packing [2]).
Perchloric acid with not more than 50 percent acid by mass UN 1803: 8: Phenolsulfonic acid, liquid UN 1804: 8: Phenyltrichlorosilane: UN 1805: 8: Phosphoric acid: UN 1806: 8: Phosphorus pentachloride: UN 1807: 8: Phosphorus pentoxide: UN 1808: 8: Phosphorus tribromide: UN 1809: 6.1: Phosphorus trichloride: UN 1810: 8: Phosphorus oxychloride: UN ...
Phosphorus pentoxide is a notable exception in that it is not dehydrated by sulfuric acid but, to the contrary, dehydrates sulfuric acid to sulfur trioxide. Upon addition of sulfuric acid to water, a considerable amount of heat is released; thus, the reverse procedure of adding water to the acid is generally avoided since the heat released may ...
Since the ends are condensed, its formula has one less H 2 O (water) than tripolyphosphoric acid. The general formula of a phosphoric acid is H n−2x+2 P n O 3n−x+1, where n is the number of phosphorus atoms and x is the number of fundamental cycles in the molecule's structure; that is, the minimum number of bonds that would have to be ...
Hydrogen fluoride can be made from concentrated sulfuric acid and e.g. calcium fluoride; Hydrogen bromide can be prepared from bromides with concentrated phosphoric acid (conc. sulfuric acid is too oxidizing) A version of the apparatus can be used for reaction between two liquid precursors.
A small amount of the sample is acidified with concentrated nitric acid, to which a little ammonium molybdate is added. The presence of phosphate ions is indicated by the formation of a bright yellow precipitate layer of ammonium phosphomolybdate. The appearance of the precipitate can be facilitated by gentle heating.
The sulfonation is reversed above 220 °C. Dehydration with phosphorus pentoxide gives benzenesulfonic acid anhydride ((C 6 H 5 SO 2) 2 O). Conversion to the corresponding benzenesulfonyl chloride (C 6 H 5 SO 2 Cl) is effected with phosphorus pentachloride. It is a strong acid, being almost fully dissociated in water.
In a variation the reaction of phenols and beta-ketoesters and phosphorus pentoxide yields a chromone.This reaction is called Simonis chromone cyclization. [6] [7] The ketone in the ketoester is activated by P 2 O 5 for reaction with the phenol hydroxyl group first, the ester group in it is then activated for electrophilic attack of the arene.