Synthesis
Input 100g of glacial acetic acid into the reaction kettle, and then input 100g of L-proline under stirring to obtain the reaction solution. After the reaction solution was stirred and warmed to 70-75C, it was kept warm and stirred for 3h to make the L-proline fully racemic, which in turn made the reaction solution have a spin of 0, and at this time, the reaction solution was reddish-brown in color.
The reaction solution with spin 0 was cooled to 30 , and then moved to the distillation kettle for distillation under reduced pressure, the temperature of distillation was at 55-60 , the vapor pressure was 0.1MPa, and the distillation was continued for 30min after distillation until there was no liquid effluent, and then the residue of distillation was concentrated to 10% of the original volume to obtain the viscous concentrate A.
The concentrate A was mixed with 120g of isopropanol, stirred until the crystals precipitated completely, then cooled down to 15C, centrifuged to remove excess liquid, and the crystals were rinsed with isopropanol to obtain the crude product.
Mix 90g of crude product, 5g of activated carbon, 185g of water and stir to raise the temperature to 70, keep warm and stir for 30min to make the crude product dissolve completely, then filter to remove the activated carbon. The residue without activated carbon after filtration was concentrated to 20% of the original volume to obtain a viscous concentrate B.
The concentrate B was mixed with 285g of isopropanol, stirred until the crystals precipitated completely, then cooled to 15C, centrifuged to remove the excess liquid, rinsed the crystals with isopropanol, and after rinsing, the crystals were dried at 80C for 12h to obtain the sample of DL-proline.
