[Bromometric assay of alprenolol and oxprenolol].

Alprenolol (1a) reacts with an excess of bromine to yield the tribromo derivative 3a by addition and monosubstitution, while applying oxprenolol (1b) the disubstituted tetrabromo derivative 2b is obtained. The N-dealkylated substance 3c was isolated as a by-product. Heating the compounds 2b and 3a with potassium hydroxide in acetone gives the 2-bromoallyl derivatives 5. Using potassium tert-butanolate the 2-propyne 7 is formed from 3a. The different colours, obtained from 1a, 1b, pindolol and propranolol with perchloric acid in acetic acid or conc. sulfuric acid, are suitable for the identification test in the European Pharmacopoeia.