General procedure for the synthesis of 3-cyanopropylisothiourea hydrochloride from 4-chlorobutanenitrile and thiourea: γ-chlorobutanenitrile (50 g, 48±3 mmol) and thiourea (4.04 g, 53.1 mmol) were dissolved in 40 mL of water. The reaction mixture was heated to reflux for 3 to 4 hours. After completion of the reaction, the water was removed by evaporation, 20 mL of ethanol was added and evaporated again, and this operation was repeated three times. Subsequently, 10 mL of methanol and 30 mL of acetone were added to the residue and the mixture was stirred for 1 hour. The crystalline product was collected by filtration and dried under high vacuum overnight. A final 5.44 g (30.3 mmol, yield 62 ± 7%) of white crystalline product was obtained with a melting point of 134-135 °C and a purity greater than 97%. The product was confirmed by 1H NMR (300 MHz, d6-DMSO): δ 1.89 (m, 2H), 2.63 (t, 2H, J = 7.2 Hz), 3.23 (t, 2H, J = 7.2 Hz), 3.38 (s, 3H). 13C NMR (75 MHz, d6-DMSO) δ 15.3, 25.0, 28.8, 119.8 , 169.7. molecular formula C5H10ClN3S, exact mass 179.03. mass spectral analysis showed m/z 179.03 (100.0%), 181.03 (32.1%), 180.03 (7.4%), 181.02 (4.5%), 182.03 (2.0%), 183.02 (1.5%). Elemental analysis calculated values (%): C 33.42, H 5.61, Cl 19.73, N 23.39, S 17.85; measured values: C 33.44, H 5.48, N 23.40, S 18.31.
