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Phosphorus pentabromide is a reactive, yellow solid of formula P Br 5, which has the structure [PBr 4] + Br − (tetrabromophosphonium bromide) in the solid state but in the vapor phase is completely dissociated to PBr 3 and Br 2.
Phosphorus pentachloride, phosphorus pentabromide, and phosphorus heptabromide are ionic in the solid and liquid states; PCl 5 is formulated as PCl 4 + PCl 6 –, but in contrast, PBr 5 is formulated as PBr 4 + Br −, and PBr 7 is formulated as PBr 4 + Br 3 −. They are widely used as chlorinating and brominating agents in organic chemistry.
PBr 3 is prepared by treating red phosphorus with bromine. An excess of phosphorus is used in order to prevent formation of PBr 5: [1] [2] P 4 + 6 Br 2 → 4 PBr 3. Because the reaction is highly exothermic, it is often conducted in the presence of a diluent such as PBr 3. Phosphorus tribromide is also generated in situ from red phosphorus and ...
Phosphoryl bromide is prepared by the reaction between phosphorus pentabromide and phosphorus pentoxide: [4] [5]. 3 PBr 5 + P 2 O 5 → 5 POBr 3. It can also be prepared via the slow addition of liquid bromine to phosphorus tribromide at 0 °C, followed by the slow addition of water and vacuum distillation of the resulting slurry.
The secondary amide 1 reacts via its enolized form with phosphorus pentachloride to form the oxonium ion 2. This produces a chloride ion which deprotonates the oxonium ion to form and imine 3 and hydrogen chloride. These then react with one another to form an amine, with loss of the phosphorus chloride residue.
[2] [3] This reaction is widely used for the synthesis of various phosphonates, phosphinates, and phosphine oxides. Several reviews have been published. [4] [5] The reaction also occurs for coordinated phosphite ligands, as illustrated by the demethylation of {(C 5 H 5)Co[(CH 3 O) 3 P] 3} 2+ to give {(C 5 H 5)Co[(CH 3 O) 2 PO] 3} −, which is ...
The fact that a reaction is thermodynamically possible does not mean that it will actually occur. A mixture of hydrogen gas and oxygen gas does not spontaneously ignite. It is necessary either to supply an activation energy or to lower the intrinsic activation energy of the system, in order to make most biochemical reactions proceed at a useful ...
Phosphorus pentabromide; Phosphorus tribromide This page was last edited on 30 October 2022, at 12:54 (UTC). Text is available under the Creative Commons ...