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-l-thia-5-azacyclooctane-l-oxide (TACO) has been studied by X-ray, microscopic, and differential scanning calorimetric methods. The transformation from the α- to the β-form occurs in the range 8–11°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 α to β is much faster than the reverse process. Evidence was also obtained for the involvement of an intermediate state in the transformation β to α.