Polarographic reduction of maleic anhydride, maleate and fumerate in pyridine

Maleic and fumaric acids in pyridine show only the reduction behaviour of the pyridinium ion, which is produced when any Bronsted acid of aqueous pKa less than ca 9 is dissolved in pyridine. The diethyl esters each show two one-electron waves, which pattern is characteristic for the electrochemical reduction of double bonds in proton-poor solvents. Maleic anhydride, which is a dihydrofuran, shows initially a single wave at a potential considerably more positive than the reduction potential of diethyl maleate; with time, a second maleic anhydride wave appears and grows at the expense of the first wave. The anhydride slowly reacts with the trace of moisture in the solvent to form maleic acid, which behaves as already indicated.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33366/1/0000764.pd