urea in neat (no solvent) heating (220-230°C, within 1.5 h, N2 atmosphere), heating (220-230°C, 3 h), cooling; extn. (1.cyclohexane, 2.CHCl3), evapn. (vac.), treatment with dild. NaOH (10 min, 60°C), filtn., washing (H2O and dild. HCl), washing (H2O), dissolution (CHCl3), chromy. (Al2O3, CHCl3), evapn., heating (vac., 150-200°C); elem. anal.;