Alkyl bromides are prepared by constant boiling with HBr (48%). This method ensures the synthesis of alkyl bromides in good yields by maintaining a consistent concentration of hydrobromic acid throughout the reaction.
What method is employed for the preparation of alkyl bromides, and why is constant boiling with HBr (48%) specifically used?
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The preparation of alkyl bromides often involves constant boiling with hydrobromic acid (HBr, 48%). This method is employed for the selective bromination of alcohols and can be facilitated by the use of phosphorus tribromide (PBr₃) or red phosphorus and bromine. Constant boiling ensures the continuous removal of the generated hydrobromic acid, preventing its buildup and promoting the forward reaction. The use of 48% HBr provides a well-defined concentration, balancing reactivity and handling considerations. This method is valuable for the synthesis of alkyl bromides from alcohols due to its selectivity and control over the reaction conditions.