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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]).
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 ...
Sulfuric acid is produced from sulfur trioxide which is obtained by oxidation of sulfur dioxide. Food-grade phosphates are generated via oxidation of white phosphorus. Carbon monoxide in automobile exhaust is converted to carbon dioxide in catalytic converters.
Carbonic acid is an illustrative example of the Lewis acidity of an acidic oxide. CO 2 + 2OH − ⇌ HCO 3 − + OH − ⇌ CO 3 2− + H 2 O. This property is a key reason for keeping alkali chemicals well sealed from the atmosphere, as long-term exposure to carbon dioxide in the air can degrade the material.
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.
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.
Example of phosphoric acid production. Wet-process phosphoric acid is prepared by adding sulfuric acid (H 2 SO 4) to apatite or tricalcium phosphate rock resulting in the following reaction: 3 H 2 SO 4 + Ca 3 (PO 4) 2 + 6 H 2 O ↔ 2 H 3 PO 4 + 3 CaSO 4 •2H 2 O Wet-process acid has to be purified by removing fluorine and other undesirable ...
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.
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