Т 55 (9) ИЗВЕСТИЯ ВЫСШИХ УЧЕБНЫХ ЗАВЕДЕНИЙ ХИМИЯ И ХИМИЧЕСКАЯ ТЕХНОЛОГИЯ R. Jasiński*, V.A. Sharnin**, A. Barański* UV SPECTRA OF E-2-ARYL-1-CYANO-1-NITROETHENES (*Institute of Organic Chemistry and Technology, Cracow University of Technology **Ivanovo State University of Chemistry and Technology) e-mail: radomir@chemia.pk.edu.pl Even though E-2-phenyl-1-cyano-1-nitroethene and its phenyl ring-substituted analogues have been known for a long time [1], their electronic spectra have not been studied so far. <...> The understanding of the nature of electronic transitions in these nitroalkenes is necessary for predicting their reactivity in [4+2]π-electron cycloaddition reactions based on the PMO theory [2-4]. <...> Hence, in the present study we recorded UV spectra of model 2-aryl-1-cyano-1-nitroethenes 1-3 and we discuss them based on calculations with the semiempirical quantum-chemical ZINDO (CI26) method [9]. <...> We successfully pursued a similar approach earlier [10] for the analysis of UV spectra of E-2arylnitroethenes and obtained predictions of their reactivity consistent with experimental results. <...> NC C C R NO2 H R = -OCH3 (1), -Cl (2), -COOCH3 (3) Key words: UV spectra, nitroalkene, e-2-aryl-1-cyano-1-nitroethene, reactivity consistent RESULTS AND DISCUSSION the The detailed analysis of UV spectra of E-2aryl-1-cyano-1-nitroethenes 1-3 proved that irrespective of the type of substituents in the phenyl ring, the spectra practically contain two absorption bands only (Fig. 1, table). <...> Their contours and location of the maximum (λmax) of the first one are very similar to the UV spectra of E-2phenyl-1-nitroethenes studied earlier [10-12]. <...> However, the location of the λmax for the second band is shifted by 20-30 nm towards longer wavelengths. <...> Therefore, according to Burawoy’s terminology [13], the long-wave bands are interpreted as B bands, while the short-wave ones as E2 bands. <...> The weak K band typical of aromatic rings is not visible in the test compound spectra. <...> Quantum-mechanical calculations show that the presence of absorption bands in the UV spectra of nitroethenes 1-3 is related in each case to the existence of five electron transitions. <...> The strongest transitions (f=0.542-0.767) occur at 340-365 nm and correspond to the excitation of an electron from an HOMO ( m) at the aromatic ring carbon atoms and 2012 Fig. 1. <...> UV spectra of E-2-p-chlorophenyl-1-cyano-1-nitroethene <...>