Supramolecular metathesis: co-former exchange in co-crystals of pyrazine with (R,R)-, (S,S)-, (R,S)- and (S,S/R,R)-tartaric acid

Co-crystals of dextro-(R, R), levo-(S,S), meso-(R,S) and racemic (R,R-S,S)-tartaric acid with pyrazine were obtained by manual kneading and slurry experiments; subsequent reactions in the solid state between these co-crystals and the various forms of tartaric acid in the solid state and via slurry show that co-former exchange takes place according to the sequence of stability [(R, S)-ta](2) .py > (S,S/R,R)-ta . py > (R,R)-ta . py or (S,S)-ta . py.