Reduction of maleate and fumarate by the CO2.- anion radical

The radical anion CO2.- reacts with fumarate and maleate at pH 5.3 mainly via electron transfer. The final products are a mixture of (−O2CCH2-)2, trans-(−O2CCH)2 and products with higher molecular weight. At higher pHs, the yield of fumarate and succinate decreases. The results suggest that though the radical anions formed by the reduction of fumarate and maleate have different structures, the final products are probably the same.

Graphical abstractCO2.-+maleate→(I/II+CO2)/.CH(CO2-)CH(CO2-)2CO2.-+fumarate→(III/IV+CO2)/.CH(CO2-)CH(CO2-)2