Effect of substituent position on assembly of compounds bearing ortho/para over meta directing groups

Introducing a second chlorine substituent at the ortho or para positions of the phenyl ring offers an alternative structural variant. However, placing the additional chlorine atom at the meta position results in the same molecular packing arrangement. • Structural Variation. • Crystal Design. • Versatile Strategy. • Crystal Engineering. This research investigated the impact of substituent location on intermolecular interactions and crystal packing. A class of N -(dichlorophenyl)-2-pyrazincarboxamide derivatives were synthesized and characterized: 2,5-dichloro ( 2,5-diCl ), 3,4-dichloro ( 3,4-diCl ), and 2,4-dichloro ( 2,4-diCl ). Comparison with their monochloro counterparts (2-chloro ( 2-Cl ), 3-chloro ( 3-Cl ), and 4-chloro ( 4-Cl )) revealed a distinct structural variation upon introducing a second chlorine substituent at the ortho / para positions of the phenyl ring. Conversely, incorporating a second chlorine atom at the meta position resulted in similar molecular packing. These findings suggest that ortho / para directing groups play a dominant role in dictating the crystal assemblies of the studied compounds.