Polarographic reduction of some derivatives of chalcone

Abstract

The derivatives of chalcone listed in Table 1 were investigated by the method of classical polarography in mixtures of Britton-Robinson buffers and ethanol (1 : 1) of pH 2.68–12.4. Although the reduction of the compounds was much the same as described for chalcone some differences were found and are discussed. Essentially, two one-electron waves were obtained which correspond to the reduction of the ethylenic linkage to dihydro derivatives. Some compounds give an additional wave in alkaline medium the height of which depends on pH; the wave corresponds to the reduction of carbonyl group to a secondary alcohol. In alkaline medium the reduction was accompanied by hydration of the ethylenic linkage and then the hydration products of the electroactive species with the OH group in position 2′ cyclized at pH 12.4 to corresponding chromanone derivatives, which were reduced in one two-electron wave. Approximate hammett constants σ were calculated for EtOCOCH 2O and H 2NOCOCH 2O groups from polarographic data as −0.22 and −0.09, respectively.