PH-Dependent Crystallization of 2-, 4-, 5-, and 6-Hydroxynicotinic Acids in Aqueous Media

Abstract

2-, 4-, 5-, and 6-hydroxynicotinic acids were crystallized in a pH-dependent manner using only water as the preferred solvent. The crystallization outcome was quite diverse: individual crystals of different sizes and shapes, microcrystalline powders, crystalline aggregates, and almost amorphous solids. Such a variety of solid forms demonstrates the relevance of pH control during crystallization processes.