General procedure for the synthesis of imidazole-2-carboxylic acid from 2-imidazolecarboxaldehyde: 30% aqueous H2O2 solution (10 g) was slowly added dropwise to stirred aqueous 2-imidazolecarboxaldehyde (2.88 g, 0.030 mol) solution (10 ml). The reaction was continued at room temperature for 72 hours. After completion of the reaction, water was removed by distillation under reduced pressure at room temperature to give a white crystalline solid. The resulting solid was washed with stirred diethyl ether/water (4:1) mixture to remove residual peroxide. Note: Heating may cause decarboxylation to occur. The yield was 97.5%. Melting point (MP) was 156-158 °C. 1H NMR (400 MHz, D2O): δ 7.56 (2H, s, imidazolium ring-H); 13C NMR (400 MHz, D2O): δ 158.86, 141.02, 120.49 ppm. IR (KBr, cm-1): 3392 (m), 3124 (m), 2861 ( m), 1618 (s), 1502 (m), 1462 (m), 1421 (s), 1388 (s), 1322 (m), 1108 (s), 925 (s), 910 (s), 819 (m), 797 (s), 774 (m). Calculated values for elemental analysis (C4H6N2O3, 130.11): C, 36.92%; H, 4.65%; N, 21.53%. Measured values: C, 37.18%; H, 4.94%; N, 21.47%.
