Magda F. Fathalla

Reaction of 4-chloro-3,5-dinitrobenzotrifluoride with aniline derivatives. Substituent effects

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.

Kinetics of the alkaline hydrolysis of 2-thioaryl-3, 5-dinitropyridine derivatives in 50% v/v DMSO-water

The kinetics of the alkaline hydrolysis of substituted 2-thioaryl-3,5-dinitropyridine have been studied in 50% DMSO– water. The observed rate constants and the second order rate constants were calculated. The thermodynamic parameters for the unsubstituted compound reveals the activating power of the two nitro- and aza-groups.

Kinetics of the nucleophilic substitution reactions of methyl 2,4-dichloro-3,5-dinitrobenzoate with piperidine, piperazine, morpholine and thiomorpholine in methanol and benzene

The kinetic of the nucleophilic substitution of methyl 2,4-dichloro-3,5-dinitrobenzoate with piperidine, piperazine, morpholine and thiomorpholine in methanol and benzene were determined spectrophotometrically at different amine concentrations and at temperatures ranging from 25 to 45 °C. The second order rate constants and the thermodynamic parameters show that the reactions are not amine catalysed and are greatly dependent of the nature of solvent and amine. UV, IR, 1H NMR, and elemental analysis are used to prove the aminodechlorination at C–2.

Kinetics of the Micellar Effects on the Alkaline Hydrolysis of 2-Chloro-quinoxaline in Acetonitrile-Water Mixtures at 35°C

Pseudo-first-order reaction rate for alkaline hydrolysis of 2-chloroquinoxaline (2-CQX) is carried out in acetonitrile (AN)-water (H2O) mixtures at 35°C. Cationic surfactants as dodecyltrimethylammonium bromide (DOTAB) and an anionic surfactant as sodium dodecylsulphate (SDS) are used above their critical micelle concentration (cmc) to study the effect of micelles on reaction rate. When increasing the percentage of volume of AN, the rate profiles with DOTAB are shown to slightly increase with increasing surfactant concentration, while that with SDS are found to smoothly decrease. The micellar effect is explained in terms of a modified pseudo-phase ion exchange model. The binding constant (KS) between 2-CQX and DOTAB as micelle showed a decrease by increasing percentage of volume of AN, while that with SDS increased. The counterion micellar coverage degrees (β) are found to be 0.55 and 0.85 with DOTAB and SDS systems, respectively, at all range of volume percentage of AN. Finally, the calculated ratio between rate constants in water to that in the micelle region kw/kM at different volume percentage of AN indicated that DOTAB enhances the reaction rate while SDS inhibits it.