Influence of the process on the mechanisms and the performances of the preferential crystallization: Example with (+/-)-5-(4-bromophenyl)-5-methylhydantoin

Resolution of the title compound is carried out at a two liter scale via tw o different processes of preferential crystallization (PC), the Auto Seeded Programmed Polythermic Preferential Crystallization (AS3PC) process and th e classical Seeded Isothermal Preferential Crystallization (SIPC) process. The ratio, crystal growth rate/secondary nucleation rate, is strongly under the influence of the process. Consequently AS3PC process appears more effi cient than SIPC process in terms of purity of the crops (optical purity), y ield, easiness of scale up and downstream operations such as filterability.