Solid state reactions of organic compounds have been extensively studied for the last decade. It is proved that the crystal structure analysis is a very powerful tool in the elucidation of the reaction mechanism. The control of the reactions by the crystal. line field has been insisted by many investigators. We have found the crystalline-state racemization of cobaloxime complexes by X-ray exposure. The chiral group bonded to the cobalt atom in a single crystal is racemized without degradation of the crystallinity. Three types of the racemization have been found till now. We have defined the cavity for the reacting group, and concluded that the rate of the reaction is closely related tc the volume and the shape of the cavity at different temperatures or in different crys-tals. These findings will serve to elucidate the mechanisms not only in the solid state reaction but also in the reactions of the clathrate compounds and enzymes.
