EXPERIMENTAL STUDIES ON THE SINGLE-CRYSTAL TO SINGLE-CRYSTAL TRANSFORMATION OF 5-METHYL-1-THIA-5-AZACYCLOOCTANE-1-OXIDE (TACO) PERCHLORATE - EVIDENCE FOR AN INTERMEDIATE STATE

The single crystal transformation of the perchlorate salt of 5-methyl-1-thia-5-azacyclooctane-1-oxide (TACO) was studied by X-ray, microscopic, and differential scanning calorimetric methods. The transformation from the alpha - to the beta -form occurs in the range 8-11 degree C, and is reversible, topotactic, and takes place without apparent change in the shape, appearance, or ability to diffract of a single crystal. The heat of transition is 0. 6 Kcals/mole. From an examination of the intensities of X-ray reflections as the transition takes place, it was shown that the transition alpha to beta is much faster than the reverse process. Evidence was also obtained for the involvement of an intermediate state in the transformation beta to alpha .