Purification of Nitrophenols Using Complex-Assisted Crystallization

Solution-phase chemical complexation can be used to enhance the purity of crystallized products. Using the separation of nitrophenol isomers as a model, we experimentally demonstrated that complex-assisted crystallization can efficiently remove structural isomers as impurities without affecting product crystal form or decreasing yield. Experiments showed that lattice-impurity incorporation of 3-nitrophenol into 4-nitrophenol can be prevented in an aqueous system using guanidine acetic acid as a complexing agent. Purity enhancements of 70% (mass) with respect to non-complexed controls were observed with no yield reduction. These results serve to further the known applicability of complex-assisted crystallization as a technique for enhancing tradtional crystallization processes.