Effect of the polymorphic form of the seeds on the preferential crystallisation

Abstract
The 5(4'-methylphenyl)-5-methyl-hydantoin (17H) is known to crystallise in two polymorphic forms, α and β. Crystallographic parameters and molecular structure of the 17H polymorphs (orthorhombic and monoclinic forms) were first investigated. Then, the main kinetical parameters of the polymorphic transition are presented. The transition rate is so low that different seeding experiments can be undertaken. Seeded Isothermal Preferential Crystallisation (SIPC) method was applied to perform the separation of the enantiomers at a 2 L scale with two types of seeds, monoclinic and orthorhombic. Orthorhombic form was never obtained in the crops but the physical parameters of the crystals produced (size, form, . ..) were strongly affected by the nature of the polymorph seeds.