Free radical products in X-irradiated Rochelle salt: low temperature ENDOR and DFT studies

► Crystalline Rochelle salt was X-irradiated at 10 K and studied using EMR techniques. ► Interpretation of present and previous data was aided by cluster DFT calculations. ► Regioselective reduction and non-selective oxidation apparently occur at 10 K. ► Thermally induced free radical reactions were followed to provide reaction mechanisms. ► A complete solid-state radical reaction scheme for (di)carboxylic acids is proposed.