Hydrogen, reaction with bromine sulphur

On heating with PCI3, the fluorine is replaced by chlorine and a mixed trihalide is produced. A mixed trihalide also results when a hydrogen halide is used. If dimethylamino difluorophosphine is treated with chlorine or bromine at low temperatures, a pentaphosphorane is produced, which will in turn react with sulphur dioxide to give dimethylamino fluorophosphine oxide. A 6-coordinated phosphoride anion is obtained in a reaction with KHF2 (7.107). 

With bromine in oleum containing 65 per cent of sulphur trioxide, at 130°, pyridine gives 3-bromopyridine. The sulphur trioxide oxidizes the hydrogen bromide formed, and the reaction follows the equation 2G5H5N + 2SO3 + Bra = 2GsH4BrN + SO2 + H2SO4... 

Liquid-liquid reactions occur between two or more liquid phases whereby a system consisting of an organic and an aqueous phase is applied most frequently. Usually reaction takes place in one phase only. Phase-transfer catalysts are sometimes used to make transfer of a reactant to the reacting phase easier. Among typical liquid-liquid reactions utilized in fine chemicals manufacture are nitrations with mixtures of nitric and sulphuric acid, conventional hydroxylations performed with hydrogen peroxide, esterifications, alkylations, brominations, and iodinations. 

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