Interaction of trialkyl phosphates and boron tribromide

Abstract

Trialkyl phosphates react with boron tribromide to yield alkyl bromides and a residue which affords tetragonal boron phosphate on ignition above 520°. Alkyl halide formation is more rapid than with boron trichloride. The isomeric purity of the bromides first formed is in accord with intermediate complex formation rather than bromine–alkoxyl exchange, at least for the n-alkyl esters and for tri-1-methylheptyl phosphate in petroleum solvent. In the absence of solvent, s-alkyl esters (1-methylbutyl, 1-ethylpropyl, and 1-methylheptyl) give bromides with much rearrangement.