Monomer-dimer equilibrium of nitroso compounds was investigated in the solid state under cryogenic photochemical conditions. It was found that nitroso dimers can be UV-photolytically converted to nitroso monomers at 12 K, and reverted to dimers by visible light irradiation or warming above 170 K. Such a photothermal "chemical switch", by which it is possible to break the chemical bond between two nitrogen atoms and bind them again, could eventually be used in supramolecular self-assembly systems. The reaction is very efficient and controlled by topochemical factors. This phenomenon was studied spectroscopically in a series of cyclic and polycyclic nitroso compounds.

Abstract. Photothermal reactions of the dimers of nitrosobenzene, m-chloronitrosobenzene, and pchloronitrosobenzene 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 followed by thermal dimerization) could successively be performed also with Z-configured dimeric nitrosobenzene. Halonitrosobenzenes dimers with E-configuration afforded different photo behavior depending on the position of halogen atom on the benzene ring: while m-halonitrosobenzenes do not dissociate under UV irradiation, 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)

Chemical characteristics of raw and processed Istarski pršut (PDO) produced from two different pig genotypes were studied with special emphasis on amino and fatty acid composition and factors of lipid stability. Raw hams of Large White (LW)xLandrace (L), and (LWxL)xDuroc (D) pig genotypes were used in the study (20 hams of each genotype). All left raw hams from each carcass were processed in accordance with the PDO specification of Istarski pršut, and other half (the right ones) of LWxL)xD genotype were used for analyses of raw hams (fresh muscles). Istarski pršut was evaluated on the basis of the chemical parameters of the raw and matured lean ham. The process of dry curing significantly influenced the chemical properties of Istarski pršut. Despite the higher content of intramuscular fat and polyunsaturated fatty acids, the fat of (LWxL)xD ham was much more resistant to hydrolysis and oxidation, suggesting that fatty acid profile and other factors, also play a significant role. Significant differences between pig genotypes in the amino acid and fatty acid profiles were found. The analyzed Istarski pršut may be distinguished by prints of multivariate chemometric statistical analysis, based on their amino acid and fatty acid compositions.

Mechanical treatment (milling) of crystals of aromatic nitroso dimers (azodioxides) induces their dissociation and cross‐dimerizations. The mechanisms of these processes are discussed on the basis of kinetic studies and the solid‐state 15 N kinetic isotope effect, which is measured for the first time. By comparison with analogous processes in cocrystals and in melts, it appears that the reactions follow similar mechanism in which the surface deformations play the crucial role. The system can also be used as a model for a more general conceptual study of solid‐state reaction mechanisms. Copyright © 2013 John Wiley & Sons, Ltd.