Crystal packing and crystallization tendency from the melt of 2-((2-ethylphenyl)amino)nicotinic acid

2-((2-ethylphenyl)amino)nicotinic acid (2EPNA) was synthesized and its crystal structure was determined. It was observed that alkylation of the phenyl ring with ethyl group disrupts the planar conformation of the molecule by steric repulsion, resulting in formation of an acid-pyridine heterosynthon (instead of acid-acid homosynthon) in the crystal. Crystallization tendency from the melt state of the polymorph was studied by differential scanning calorimetry (DSC). It was revealed that this compound could form a very stable amorphous phase on melt quenching and not crystallize even on re-heating. The formation of acid-pyridine hydrogen bonding in the amorphous state is believed to be responsible for its good glass forming ability.