Directing the Viedma ripening of ethylenediammonium sulfate using "Tailor-made" chiral additives.

Both enantiomers of trans-cyclohexane-1,2-diammonium sulfate and trans-1,2-diphenylethylenediammonium sulfate were used as "tailor-made" additives to direct the mirror-symmetry breaking in the attrition-enhanced deracemization (i.e. Viedma ripening) of conglomerate crystals of ethylenediammonium sulfate (EDS). Isothermal titration calorimetry (ITC) shows chiral recognition of (1R,2R)- and (1S,2S)-1,2-diphenylethylenediamine to EDS crystals where the enthalpy of adsorption of the (1R,2R)-isomer on l-EDS crystals is higher in comparison to that on d-EDS crystals. These results are consistent with a "rule of reversal" mechanism driving the chiral outcome of the Viedma ripening of EDS.