Pyrrolidone hydrotribromide: a brominating agent with selectivity for ketones

The relative reactivities of a ketone, an olefin, and an enol acetate towards bromination in tetrahydrofuran by "pyrrolidone-bromine complex", (pyrrolidone) 3 *HBr 3 (PHT), are acetate. The conversion of benzalacetone to C 6 H 5 CH = CHCOCH 2 Br is given as an example. The selectivity of P...

Full description

Saved in:
Bibliographic Details
Published inCanadian journal of chemistry Vol. 47; no. 4; pp. 706 - 709
Main Authors Awang, D. V. C, Wolfe, Saul
Format Journal Article
LanguageEnglish
Published Ottawa, Canada NRC Research Press 15.02.1969
Online AccessGet full text

Cover

More Information
Summary:The relative reactivities of a ketone, an olefin, and an enol acetate towards bromination in tetrahydrofuran by "pyrrolidone-bromine complex", (pyrrolidone) 3 *HBr 3 (PHT), are acetate. The conversion of benzalacetone to C 6 H 5 CH = CHCOCH 2 Br is given as an example. The selectivity of PHT is enhanced by dilution and is diminished upon addition of pyrrolidone to the reaction mixtures. The selectivity of phenyltrimethylammonium tribromide (PTAT) is not as great as that of PHT and is subject to acid catalysis.At a sufficiently low concentration in a nonpolar solvent, the enol of cyclohexanone reacts at least 1 000 000 times faster with molecular bromine than does cyclohexene. This observation suggests that the selectivity of perbromides may be due to their ability to furnish a low equilibrium concentration of bromine when dissolved in solvents of low polarity.
ISSN:0008-4042
1480-3291
DOI:10.1139/v69-113