engleski

Selectivity of Nitrosobenzene Heterodimerization Reaction

It is well known that nitrosobenzenes can exist in three distinct molecular forms: monomeric, (Z)-dimeric and (E)-dimeric form. In the solid state most of them exist as dimers, while in solution monomer-dimer equilibrium is established. At ambient temperature the main solution species are monomers while decreasing temperature favours the dimeric azodioxy species with both (Z)- and (E)-forms present in addition to the monomer. The property of dimerization reaction of nitroso compounds to azodioxides could be used for the construction of novel supramolecular structures based on nitroso compounds as building blocks. In this work we are presenting a selectivity study of dimerization reaction (i.e. heterodimerization) of nitroso monomers to asymetrically substituted azodioxybenzenes (i.e. heterodimers) in cases when they are not sterically crowded with large groups in ortho-position which was previously stated as the necessary condition for heterodimer formation. The selectivity study of heterodimerization reaction was carried out both in solution and in the solid state by means of NMR and FTIR spectroscopy in the series of para- and meta-substituted nitrosobenzenes. We have shown that nitrosobenzenes can form heterodimers in solution as well as in the solid state even when they are not sterically crowded with large groups in ortho-position. As it was observed by NMR and FTIR spectroscopy, selectivity of heterodimerization reaction is quite different in the solid state from that in solution because of a considerable influence of packing factors in the former. DFT computational study of heterodimers formation was also undertaken.

nitrosobenzene; heterodimers; reactivity; selectivity

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