Stage A: Synthesis of 5-hydroxynicotinic acid
1. 10.1 g (0.05 mol) of 5-bromonicotinic acid, 10 g of NaOH (dissolved in 63 mL of water), 3.1 g of calcium sulfate pentahydrate, and 0.42 g of copper powder (0-valent) were added to a reaction flask.
2. The reaction mixture was stirred vigorously and heated under reflux conditions for 30 hours.
3. Upon completion of the reaction, the mixture was cooled to room temperature, 4.8 g Na2S-H2O was added and stirring was continued overnight.
4. The reaction mixture was heated to 70 °C and treated by passing H2S gas until the white precipitate completely disappeared (about 3 hours).
5. After cooling to room temperature, the reaction mixture was filtered.
6. Adjust the pH of the filtrate to 5.2 with concentrated hydrochloric acid and filter to collect the precipitate.
7. Adjust the pH of the filtrate again to 4.6 with concentrated hydrochloric acid and filter to collect the white precipitate. 8.
8. The precipitate was washed with water and dried under reduced pressure to give 4.3 g (yield: 62%) of 5-hydroxynicotinic acid (molecular formula: C7H5NO3).
Product Characterization:
- Appearance: white powder
- Melting point: >260°C
- 1H NMR (300 MHz, DMSO-d6) δ (ppm): 8.48 (d, J=1.5Hz, 1H), 8.26 (d, J=2.6Hz, 1H), 7.51 (d, J=1.9Hz, 1H)
- IR (KBr, cm-1): 3273, 1538, 1393, 1294
