Croatica Chemica Acta, Vol. 73 No. 3, 2000.
Original scientific paper
Polarographic Kinetic Currents of Formaldehyde and Kinetics of the Electrode Chemical Reactions
Yakov I. Tur’yan
; The National Physical Laboratory of Israel, Danciger »A« Bldg., Givat Ram, Jerusalem 91904, Israel
Abstract
New approaches to the analysis of the polarographic (DCP) kinetic currents of formaldehyde have been developed. Anomalously high limiting kinetic current in strongly acidic media has been explained by catalytic hydrogen evolution upon CH2OH+ discharge after the protonation of CH2O. On the other hand, the diffusion contribution of CH2O from the bulk solution to the total limiting kinetic and diffusion currents should be taken into account for a correct determination of the rate constants of CH2(OH)2 dehydration reaction in the catalysis by H2O molecules in neutral and weakly acidic media. At the same time, the electrode reaction of the direct formation of CH2O from CH2(OH)O- can be neglected in alkaline Solutions. Thus, the two consecutive reactions, i.e. the formation of CH2(OH)2 from CH2(OH)O- and H2O and the dehydration reaction of CH2(OH)2 to CH2O, proceed at the electrode in alkaline Solutions. Detailed analyses of the diffusion coefficient and diffusion current of formaldehyde as well as equilibrium constants of the dimerization and acidic dissociation reactions of CH2(OH)2 and the hydration and protonation reactions of CH2O allowed us to choose the most correct values for kinetic calculations.
Keywords
polarographic kinetic currents; formaldehyde; electrode reactions
Hrčak ID:
132006
URI
Publication date:
4.9.2000.
Visits: 1.129 *