Polymorphism in butylated hydroxy anisole (BHA)

摘要

Single crystal X-ray analysis of butylated hydroxy anisole (BHA) reveals the existence of two polymorphs with dramatically different crystal packings sustained by OH···ether supramolecular heterosynthons: double helices (Form Ⅰ) and discrete hexameric assemblies (Form Ⅱ). Polymorphism, the ability of a substance to exist in more than one crystalline form, has always been relevant to the pharmaceutical industry since bioavailability and physical properties (solubility, dissolution rate, shelf life, etc.) can be critically dependent on crystal packing. It is also particularly topical because of intellectual property issues associated with active pharmaceutical ingredients (APIs), which lend to be predisposed to exhibit polymorphism because they inherently possess exofunctional groups that have multiple avenues for self-assembly. An analysis of polymorphism in organic crystals suggested that it is most common in molecules with more than one functional group that is capable of hydrogen bonding and/or those that contain flexible groups that are able to form strong hydrogen bonds such as OH and NH_2.