M. Shibata et P. Zuman, ELECTROREDUCTION OF THE HYDRAZIDE OF MALEIC-ACID IN AQUEOUS-SOLUTIONS, Journal of electroanalytical chemistry [1992], 420(1-2), 1997, pp. 79-87
Maleic hydrazide (3,6-dihydroxypyridazine, I) is reduced to the dicarb
onyl form I at the dropping mercury electrode in two-electron waves. T
he first wave I-1 corresponds to a reduction of a diprotonated, the se
cond I-2 of a monoprotonated, the third I-3 of an unprotonated and the
fourth I-4 of an anionic form. Exclusion of the dihydroxy form I '' a
nd the monohydroxy form I' as electroactive species was based on elect
rochemical properties and comparison of pK(a) values. Polarographic cu
rrents are limited by the rate of protonation occurring as a surface,
heterogeneous process. Wave I-1 at pH 3 to 5 is the most suitable for
analytical applications.