Cocrystallisation of succinic and fumaric acids with lutidines: a systematic study

A series of cocrystals and salts of succinic and fumaric acids and the isomers of lutidine have been prepared. The crystal structures of six lutidine - succinic acid cocrystals, four lutidine fumarate salts, and two lutidine - fumaric acid cocrystals have been determined. The crystal structures are compared and discussed in the light of similar features, particularly the formation of three-molecule base - acid - base units, which appears to be important for the stability of the crystal. The packing of these units is found to be very sensitive to methyl group position.