K. Butkiewicz
Oct 1, 1972
Citations
0
Influential Citations
6
Citations
Journal
Journal of Electroanalytical Chemistry
Abstract
Summary Using the method of classical polarography, the reduction of isomers of 1-(2-hydroxyphenyl)-3-[2(3 or 4)-pyridyl]-2-propen-1-ones and 1-(2-hydroxy-4-methoxyphenyl)-3-[2(3 or 4)-pyridyl]-2-propen-1-ones was investigated. Studies were carried out in mixtures of Britton-Robinson buffers and ethanol (1:1) in the pH range 2.6–12.15 and in 0.175 M (C 4 H 9 ) 4 NI in 75% dioxane. The compounds investigated were reduced on the DME over the whole pH range studied. Limiting currents and half-wave potentials were dependent on pH. In the pH range 2.6–8.0 the reduction followed the paths described for chalcone and showed two separate two-electron waves corresponding to the consecutive reduction of the ethylenic linkage and the carbonyl group to the corresponding dihydroderivatives and secondary alcohols, respectively. In the pH range 9.2–12.15, the reduction was accompanied by hydration of the ethylenic linkage and then the hydration products cyclized (at pH 12.15) to the corresponding chromannones which were reduced in a one two-electron wave. From the Hammett-Taft equation, the substituent σ x * constants were calculated for the 2-hydroxybenzoyl and 2-hydroxy-4-methoxybenzoyl groups; they were found to be +1.84 and +1.77, respectively.