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In modern world, there is a need to search for alternatives to antibiotics due to the growing resistance of microorganisms. Plant extracts can be a promising replacement. Due to biological functions, they can suppress the development of various processes associated with pathogenicity and virulence, in particular, the Quorum sensing process. Based on the above, the aim of the study was to assess the bioactivity of 7,8-dihydroxy-4- methylcoumarin and 20% chlortetracycline in relation to the microbial diversity of the cecum of broiler chickens. 4 groups of broiler chickens were formed for the experiment. The control group received a diet without additives (basic diet (BD)); group I - BD + 20% chlortetracycline, at the dosage 0.63 g/kg bw per day, group II - BD + 7,8-dihydroxy-4-methylcoumarin at a dose of 9.0 mcg/ kg bw per day; Group III - BD + 7,8-dihydroxy-4-methylcoumarin + 20% chlortetracycline. The NGS of the 16S rRNA gene was used as a research method. Analysis of the results showed that addition of coumarin, the antibiotic and their combination to the poultry diet had an impact on formation of the microbial composition of intestine. Moreover, there was a decrease in the number of Lactobacillaceae , Lachnospiraceae and Erysipelotrichaceae families. In addition, the proportion of opportunistic Streptococcus flora decreased more than by 10 %.

Modeling of the aniline with nitrobenzene reaction was carried out by PM6 method with tetramethylammonium hydroxide. Calculated data prove that the stage of transfer of hydride ion from the p-[sigma]-complex to the acceptor, i.e. nitrobenzene or 4- nitrodiphenylamine determines the rate of aniline with nitrobenzene condensation. Herein, intermolecular transfer mechanism that has lower activation energy is the most likely one if compared with intramolecular mechanism. It is shown that tetramethylammonium cation can form ionic and ion-dipole complexes with the components of the reaction mixture and its field influences the distribution of electron density in the reactants and their reactivity

Modeling of the condensation reaction to diphenylamine was carried out by PM7 method with acid catalysts: tetrafluoroborate, oxytrifluoroborate and anilinium oxytetratrifluoroborate. The calculated data prove that the formation of a few protonated forms of aniline is possible during the reaction of aniline with acids. Only positively charged p- and o-[sigma]-complexes are capable of further interaction with aniline. The stage of intramolecular proton transfer from the primary to the secondary amino groups of intermediates of aniline reaction with proton aniline ?-complex determines the condensation rate of aniline to diphenylamine with acid catalysts. A catalyst anion can form ionic and ion-dipole complexes with reaction mixture components and can influence the distribution of electron density in reactants and their reactivity with its field

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