pseudopolymorphs

Pseudopolymorphs are crystalline forms of a compound that resemble true polymorphs but are, in fact, different modifications arising from the same chemical substance. Unlike genuine polymorphs, which are distinct crystal structures of a single substance, pseudopolymorphs are typically the result of solvent molecules integrated into the crystal lattice, forming solvates or pseudohydrates. These can sometimes be mistaken for true polymorphs due to their similar crystal shapes and diffraction patterns.

The formation of pseudopolymorphs often involves the incorporation of solvent molecules during crystallization processes, leading to different physical and chemical properties compared to the pure compound. For example, a drug substance may exist as multiple pseudopolymorphs, each with varying solubility, stability, and bioavailability, which can significantly impact pharmaceutical formulation and efficacy.

Distinguishing between true polymorphs and pseudopolymorphs is essential in fields like pharmaceuticals and materials science. Techniques such as X-ray diffraction, thermogravimetric analysis (TGA), and infrared spectroscopy are commonly employed to identify the presence of solvent molecules and confirm the nature of the crystalline form.

While polymorphs are characterized by different arrangements of the same molecules in a crystal lattice, pseudopolymorphs are characterized by the presence of solvent molecules within the crystal structure, making them sometimes reversible upon removal of solvent. Understanding these distinctions is crucial for material stability, processing, and regulatory considerations in various industrial applications.