Solid–gas reactions. Part I. Bromination
Solid αβ-unsaturated acids, amides, and ketones yield, on exposure to bromine vapour at room temperature, the ‘trans-adduct’ in quantitative or near-quantitative yield even where addition of bromine in solution has been reported to be difficult. Polymorphic forms of several compounds differ in their rates of bromine uptake and addition. That crystal texture plays a role is suggested by the fixation of bromine in compounds which in the pure state add bromine slowly but which do so more rapidly in the presence of small amounts of impurities (e.g. photo-dimer or saturated derivatives).