The condensation of furfural with urea

The condensation of furfural with urea was conducted in aqueous and heterogeneous phases. In both of the synthetic procedures, the reaction was carried out using different furfural-urea molar ratios. The reaction in the aqueous phase was faster than the reaction in heterogeneous phase. The product's characterization was assessed by ¹H, ¹³C and ¹⁵N NMR, X-ray diffraction, FTIR, DTA, TG and DSC. The NMR spectra showed that the reaction product was always difurfurilidentriurea, independent of the furfural-urea molar ratio used in the syntheses. However, the results of X-ray diffraction study reveal differences in sample crystalinity. Thus, the products obtained from heterogeneous phase syntheses are more crystalline than those obtained from homogeneous reaction, and their cristalinity increases as the urea/furfural molar ratio increases. According to the thermal analysis, the product is stable until 160°C. The melting point, at 205°C, is accompanied by an endothermic decomposition.