Acid catalysed condensation of methyl N-phenylcarbamate

Abstract

The condensation of methyl N-phenylcarbamate with formaldehyde to methylene diphenyl diurethane has been studied in the presence of various liquid and solid acid catalysts in a batch reactor. The 50% sulphuric acid and Amberlyst 15 were found to be the best liquid and solid catalysts, respectively. Unlike liquid acid catalyst, fresh solid catalysts did not form a by-product N-benzyl compound, which was attributed to a steric hindrance imposed on a fixed proton site in solid acids. However, accumulation of water from repeated uses of the catalyst caused decreased activity and the formation of the byproduct. The deactivated catalyst could be completely regenerated by drying in vacuo. The presence of macropore was essential for a solid catalyst to be effective for the reaction. Ethyl acetate and toluene were found to be efficient solvents with the Amberlyst 15 catalyst.