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Pyridinium perbromide (also called pyridinium bromide perbromide, pyridine hydrobromide perbromide, or pyridinium tribromide) is an organic chemical composed of a pyridinium cation and a tribromide anion. It can also be considered as a complex containing pyridinium bromide—the salt of pyridine and hydrogen bromide—with an added bromine (Br ...
Tribromide is the anion with the chemical formula Br 3 −, or salts containing it: . Tetrabutylammonium tribromide; Tetrabromophosphonium tribromide; Pyridinium perbromide; Sodium and potassium tribromides can be prepared by reacting NaBr or KBr with aqueous bromine.
Pyridinium refers to the cation [C 5 H 5 NH] +. It is the conjugate acid of pyridine . Many related cations are known involving substituted pyridines, e.g. picolines, lutidines, collidines.
This lone pair does not overlap with the aromatic π-system ring, consequently pyridine is basic, having chemical properties similar to those of tertiary amines. Protonation gives pyridinium, C 5 H 5 NH +.The pK a of the conjugate acid (the pyridinium cation) is 5.25. The structures of pyridine and pyridinium are almost identical. [87]
Pyridine N-oxide is five orders of magnitude less basic than pyridine: the pK a of protonated pyridine-N-oxide is 0.8. [7] Protonated derivatives are isolable, e.g., [C 5 H 5 NOH]Cl. [3]
Pyridine-N-oxides bind to metals through the oxygen. According to X-ray crystallography, the M-O-N angle is approximately 130° in many of these complexes. As reflected by the pKa of 0.79 for C 5 H 5 NOH +, pyridine N-oxides are weakly basic ligands. Their complexes are generally high spin, hence they are kinetically labile.
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Bromoantimonates can be made using a water solution of antimony tribromide, hydrobromic acid, and an amine. Alternately antimony trioxide can be used. Variants can be made without using water, and heating the antimony tribromide with an amine hydrobromide.