No abstract

Several dimerics-triazine Schiff bases displayed more potent anti-bacterial activity compared with ampicillin trihydrate. They revealed significantly low MIC values towards the tested MDR strains and showed a high selectivity index towards antimicrobial activity againstK. pneumoniaeandMRSA1compared to mammalian cells.

The kinetics of the reaction of 2‐chloro‐3‐nitropyridine (ortho‐like) and 2‐chloro‐5‐nitropyridine (para‐like) with a series of aryloxide ions were studied in methanol at different temperatures. Plots of ΔH ≠ versus ΔS ≠ for both reactions gave good straight lines with isokinetic temperatures of 168 and 195 °C. Good linear relationships were obtained from the plots of log k 2 against σ° values with relatively large negative ρ values indicating the formation of Meisenheimer σ‐complex intermediates. Plots of log k 2 against pK a values gave good straight lines indicating that the reactions show an appreciable degree of bond formation in the transition state. An addition–elimination mechanism is suggested. Copyright © 1999 John Wiley & Sons, Ltd.

The kinetics of the reaction of substituted anilines with 2-chloro-5-nitropyridine were studied in dimethyl sulfoxide (DMSO) and dimethyl formamide (DMF) at different amine concentrations and temperatures in the range 45-60 • C. In both solvents the reaction was not a base-catalyzed one. A plot of H # versus S # for the reaction in DMSO and DMF gave good straight lines with isokinetic temperatures 128 • C and 105 • C, respectively. Good linear relationships were obtained from the plots of log k 1 against σ • values at all temperatures with negative ρ values (−1.63 to −1.28 in DMSO) and (−1.26 to −0.90

N-(2,6-Dinitro-4-trifluoromethylphenyl)aniline derivatives were prepared by anilino-dechlorination of 4-chloro-3, 5-dinitrobenzotrifluoride. IR, UV and 1H NMR studies suggested an intramolecular hydrogen bond between the amino hydrogen and one o-nitro group. An addition-elimination mechanism was suggested based on the second-order kinetics and the dependence of rates on the nature and the position of the substituent in the aniline ring, as well as the high negative values of ρ(-3.14, −3.16, −3.01). Such values indicate a positive charge on the aniline nitrogen in the transition state and that the rate is affected by the polar effect of the substituent. The β value (0.85 at 30°C) indicates an appreciable degree of bond formation in the transition state.