This work is the extension of our preliminary communication about the relationship between the change in the solid-state structure and the chemical reaction in a crystal. The investigation is a case study about the nature of the adiabatic organic solid-state reactions by kinetic measurements of the processes that occur during the dimerization of aromatic nitroso compounds (p-bromo- and p-iodonitrosobenzenes, respectively) in crystals. From the reaction rates at different temperatures we have calculated the activation energy. Since dimerization is induced by the appearance of crystal deformations on the surface caused by sublimation, we study here the relationship between the rate of sublimation and the rate of dimerization. There are indications that the sublimation of molecules from the surface serves only for the activation of chemical solid-state reaction. Dimerization is also studied under three different topochemical environments: strong topochemistry in the cryogenic conditions where the starting monomers were obtained by photolysis of crystals of the corresponding dimer at 14 K, looser topochemistry in the freshly sublimed crystals of monomers, and randomly distributed monomer molecules in thin layers prepared by cryogenic deposition. It is demonstrated that the change in topochemistry drastically modifies the reaction rate.

Photothermal reactions of the dimers of nitrosobenzene, m-chloronitrosobenzene, and p-chloronitrosobenzene were studied in solid-state by IR spectroscopy at low temperatures and by X-ray powder diffraction. It was found for the first time that photothermal cycle (photolytic dissociation fol-lowed by thermal dimerization) could successively be performed also with Z-configured dimeric nitroso-benzene. Halonitrosobenzenes dimers with E-configuration afforded different photo behavior depending on the po-sition of halogen atom on the benzene ring: while m-halonitrosobenzenes do not dissociate under UV ir-radiation, p-chloronitrosobenzene, as well as previously studied p-bromonitrosobenzene photolyses very efficiently with recovering of the original crystal phase. Kinetics of thermal dimerization was measured in solid-state, and it was found that the reaction phase transformation occurs as a two-dimensional growth through the crystal. (doi: 10.5562/cca1714

This review is focused on the dimerization and dissociation of aromatic C-nitroso compounds and their dimers, the reactions that could be used as a convenient model for studying the thermal organic solid-state reaction mechanisms. This molecular model is simple because it includes formation or breaking of only one covalent bond between two nitrogen atoms. The crystalline molecular solids of nitroso dimers (azodioxides) dissociate by photolysis under the cryogenic conditions, and re-dimerize by slow warming. The thermal re-dimerization reaction is examined under the different topotactic conditions in crystals: disordering, surface defects, and phase transformations. Depending on the conditions, and on the molecular structure, aromatic C-nitroso compounds can associate to form one-dimensional polymeric structures and are able to self-assemble on gold surfaces.