Synthesis of 1-Phenylthiourea: An Undergraduate Organic Chemistry Experiment Illustrating Carbonyl Transformations

The practical two-step synthesis of 1-phenylthiourea is reported here as an undergraduate experiment for the organic synthesis laboratory. The reactions involved in 1-phenylthiourea preparation are very useful didactic examples to illustrate concepts relating to carbonyl substitution and addition, the effect of pH on solubility of organic compounds, and many laboratory techniques, such as isolation, purification, and product analysis. The products were purified through precipitation, which involves changing the pH value, followed by recrystallization. The products were identified by melting point and infrared and NMR spectroscopy.