Effect of solvent polarity in mechanochemistry: preparation of a conglomerate vs. racemate

Cocrystallization of racemic dl-tartaric acid (dl-ta) and achiral isoniazid (ISN) was investigated using mechanochemistry. Neat grinding (NG) and liquid-assisted grinding (LAG) in the presence of non-polar liquids result in the formation of a conglomerate (ISN center dot d-ta/ISN center dot l-ta); whereas LAG with polar liquids yields racemic salt ISN center dot dl-ta. The effect of solvent polarity and dipole moment in mechanochemistry is discussed.