Template-directed crystallization of carbamazepine form II from palmitic acid melt – a key to understand mechanically-induced polymorphism of carbamazepine

Abstract

Heating a single crystal of carbamazepine (III) (the thermodynamically stable form) in contact with solid palmitic acid resulted in the melting of palmitic acid and the growth of the crystals of carbamazepine (II) (the least stable polymorph) at the interface “carbamazepine (III) crystal–palmitic acid melt”. The study suggests a possible mechanism of the transformation of carbamazepine (III) into carbamazepine (II) on mechanical treatment with palmitic acid as an additive.