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Phosphorus tribromide, like PCl 3 and PF 3, has both properties of a Lewis base and a Lewis acid. For example, with a Lewis acid such as boron tribromide it forms stable 1 :1 adducts such as Br 3 B · PBr 3. At the same time PBr 3 can react as an electrophile or Lewis acid in many of its reactions, for example with amines.
Tribromide is the anion with the chemical formula Br 3 ... Phosphorus tribromide, PBr 3; Plutonium tribromide, PuBr 3; Praseodymium tribromide, PrBr 3;
Phase behavior Triple point? K (? °C), ? Pa Critical point? K (? °C), ? Pa Std enthalpy change of fusion, Δ fus H o? kJ/mol Std entropy change of fusion, Δ fus S oJ/(mol·K)
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.
An example of the Hell–Volhard–Zelinsky reaction can be seen in the preparation of alanine from propionic acid.In the first step, a combination of bromine and phosphorus tribromide is used in the Hell–Volhard–Zelinsky reaction to prepare 2-bromopropionic acid, [3] which in the second step is converted to a racemic mixture of the amino acid product by ammonolysis.
Thiophosphoryl bromide can be prepared by heating phosphorus tribromide with phosphorus pentasulfide, or with elemental sulfur in an inert atmosphere at 130 °C. [4] Thiophosphoryl bromide is one product of the bromination of P 4 S 7 in cold carbon disulfide: [1] 3 P 4 S 7 + 12 Br 2 → 2 PBr 3 + 2 PSBr 3 + 2 P 2 S 6 Br 2 + 2 P 2 S 5 Br 4
Phosphorus triiodide (PI 3) is an inorganic compound with the formula PI 3. A red solid, it is too unstable to be stored for long periods of time; it is, nevertheless, commercially available. [ 2 ] It is widely used in organic chemistry for converting alcohols to alkyl iodides and also serves as a powerful reducing agent.
Red phosphorus reacts with bromine and iodine to form phosphorus tribromide [14] [15] and phosphorus triiodide. Both are useful as halogenation agents, like replacing the hydroxyl group of alcohols. Phosphorus triiodide can also be used to produce hydroiodic acid after hydrolysis.