Unusual seeding effect in the liquid-assisted high-pressure polymorphism of chlorpropamide

When crystals of four polymorphs-a stable α-form and three metastable ones (β-, γ-, δ-forms)-are simultaneously present in a pressure cell, immersed in a 1:1 pentane-isopentane mixture, the least stable β-form recrystallises exclusively into the γ-form (if no δ-form seed is present) or concomitantly into the γ- and δ-forms (if a seed of the δ-form is present). However, the β-form never recrystallises to the stable α-form, even if the latter is also present as a potential seed.