General procedure: 0.01 mole of bisphenol A, 0.02 mole of NaOH and 150 ml of 10% aqueous K2CO3 were added to a 250 ml three-necked flask, and nitrogen was passed through to displace the oxygen in the flask. The reaction mixture was stirred and reacted at 100 °C for 1 hour to produce a precipitate. The precipitate was collected by filtration under nitrogen protection, washed twice with 30 mL of hot isopropanol, and subsequently dried under reduced pressure at 200°C for 3 hours to give 25.8 g of bisphenol A disodium salt in 95% yield. Example 27: 0.01 moles of bisphenol A, 0.02 moles of NaOH and 150 mL of 35% K2CO3 aqueous solution were added to a 250 mL three-necked flask, and nitrogen was passed through to displace the oxygen in the flask. The reaction mixture was stirred and reacted at 100 °C for 1 h to produce a precipitate. The precipitate was collected by filtration under nitrogen protection, washed twice with 30 mL of hot isopropanol, and subsequently dried under reduced pressure at 200 °C for 3 hours to give 25.8 g of bisphenol A disodium salt in 95% yield.
