Comparison Between Solid Catalysis and Electrochemical Catalysis in the Synthesis of Methyl Carbamate via Hofmann Rearrangement

INTRODUCTION: Hofmann rearrangement reactions are important organic reactions used to obtain carbamates, which are formed via isocyanate as an intermediate compound. Since carbamates have applications in various fields, such as pharmaceuticals, agricultural chemistry, and herbicides, this research focuses on synthesizing carbamates using environmentally friendly methods like solid catalysts and electrical techniques due to their unique characteristics in enhancing selectivity and minimizing solvents. Additionally, a comparison between the two methods was made. MATERIALS AND METHODS: In this study, two methods were employed to obtain carbamate. The first method utilized heterogeneous catalysis with sodium halide-modified aluminum oxide to achieve a high basic surface area alongside sodium hypochlorite as a safe and inexpensive oxidant. The second method employs electrochemical catalysis using a carbon anode and a zinc cathode, with sodium halides serving as intermediates. RESULTS: Sodium chloride modified with aluminum oxide demonstrated better results than sodium bromide and iodide. A higher yield of carbamates was obtained in a shorter time and at moderate temperatures. In contrast, in the electrochemical method, sodium bromide demonstrated the best performance, achieving 75% conversion under ambient conditions. CONCLUSION: The comparison between the two methods revealed that the electrochemical method significantly outperformed, as it managed to avoid side products and directed the reaction towards the target compound under mild conditions. Whereas the solid catalytic method (Al2O3/NaCl) obtained lower yields and produced side products in a shorter reaction time.