Electrochemical synthesis of 2,2-dinitropropanol

This paper describes electrochemical approaches to the synthesis of 2,2-dinitropropanol (DNPOH) and discusses the potential for pilot-plant scale synthesis. In this work, the anode of the electrochemical cell replaces the chemical oxidants used in the conventional synthesis for the purpose of reducing secondary waste and the consequent disposal cost. The electrosynthesis reactions described in this work use the common starting material, nitroethane (NE). The synthesis of the end-product DNPOH involves two steps: (1) electrochemical oxidative nitration (addition of a geminal NO₂ group); and, (2) condensation with formaldehyde. Electrochemical oxidation of NE was first attempted by direct oxidation on a Pt electrode surface resulting in low yield and significant generation of undesirable by-product. Alternatively, two different mediators were employed resulting in a dramatic improvement of yield for the oxidative nitration step. The two different mediators used, Ag⁺/Ag⁰ and Fe(CN) ₆ ^-3/-4 , were derived from the chemical oxidants known to perform the oxidative nitration. The Fe(CN) ₆ ^-3/-4 mediator demonstrated the best promise for scale-up and industrial production due to the lower cost of the mediator and the solubility of the mediator lending it to greater ease-of-use in conventional electrochemical cell designs.