Synthesis
General procedure for the synthesis of 2-chloroterephthalic acid from 2-aminoterephthalic acid:
1. a solution of sodium nitrite (3.8 g, 55 mmol) dissolved in water (18 ml) was slowly added to a suspension of 2-aminoterephthalic acid (10 g, 55 mmol) in concentrated hydrochloric acid (14.3 ml) and water (28.6 ml) at 0 to 5°C for 15 to 20 minutes.
2. After continued stirring at 0-5°C for 30 minutes, the reaction mixture was slowly added to a pre-cooled solution of cuprous chloride (12 g, 122 mmol) in concentrated hydrochloric acid (60 mL) while maintaining stirring.
3. The reaction mixture was allowed to gradually warm up to room temperature and stirring was continued for 3 hours.
4. Upon completion of the reaction, the reaction mixture was filtered and the solid product was collected and washed with ice-cold water (25 mL).
5. The crude product was dried under vacuum and then recrystallized from a solvent mixture of water and ethanol (9:1 v/v) to give 8 g of 2-chloroterephthalic acid as an off-white solid in 73% yield.
6. The structure of the product was confirmed by 1H NMR (CD3OD, δ ppm): 7.87 (1H, d, J = 7.8 Hz, Ar-H), 7.98 (1H, d, J = 7.8 Hz, Ar-H), 8.07 (1H, s, Ar-H).
References
[1] Patent: WO2010/59549, 2010, A1. Location in patent: Page/Page column 25
[2] Chemische Berichte, 1886, vol. 19, p. 1636
