Polarographic behaviour of ω-diazoacetophenones in aqueous buffer solutions

Abstract

The polarographic behaviour of ω-diazoacetophenone and 12 meta- and para-substituted ω-diazoacetophenones has been studied in aqueous buffer solutions. The polarograms generally show three waves corresponding to successive reduction of the diazo-ketone to the corresponding ω-aminoacetophenone, acetophenone, and either 2-phenylethanol or 2,3-diphenylbutane-2,3-diol. The reduction scheme may be represented: first wave, XC6H4·CO·CHN2+ 7H++ 6e → XC6H4·CO·CH2·NH2+ NH4+, second wave, XC6H4·CO·CH2·NH2+ 3H++ 2e → XC6H4·CO·CH3+ NH4+, third wave, XC6H4·CO·CH3+ 2H++ 2e → XC6H4·CH(OH)·CH3, or 2XC6H4·CO·CH3+ 2H++ 2e →[graphic omitted] where X is the meta- or para-substituent (including H). For the p-nitro-substituted compound an additional wave is observed, preceding that for the diazo-ketone reduction, and corresponding to reduction of the nitro-group.The polarographic behaviour of p-bromo-ω-diazoacetophenone and preparative controlled potential electrolysis experiments indicate that the six-electron reduction follows the scheme: XC6H4CO·CHN2+ 2H++ 2e → XC6H4CO·CH:N·NH2, XC6H4CO·CH:N·NH2+ 2H++ 2e → XC6H4CO·CH2·NH·NH2, XC6H4CO·CH2·NH·NH2+ 3H++ 2e → XC6H4CO·CH2·NH2+ NH4+