Effect of acetonitrile–water mixtures on the reaction of dinitrochlorobenzene and dinitrochlorobenzotrifluoride with hydroxide ion

Abstract

The kinetics of alkaline hydrolysis of 2-chloro-3,5-dinitrobenzotrifluoride 1 and 1-chloro-2,4-dinitrobenzene 2 were studied in various acetonitrile-water (AN-H 2 O) mixtures (10-90% w/w) at different temperatures. Thermodynamic parameters H # and S # show great variation, whereas G # appears to vary little with the solvent composition presumably due to compensating variations. The results are discussed in terms of the solvent parameters such as preferential solvation, dielectric constant, polarity/polarizability, and hydrogen bond donor and acceptor parameters. It has been found that the factors controlling the reaction rates are the desolvation of OH − , the solvophobicity of the medium, and free water molecules in rich AN mixed solvent. The data showed that the solvatochromic parameters of (AN-H 2 O) mixed solvent are destroyed in the presence of excess OH − . C

Nucleophilic Substitution Reactions of 2,4-Dinitrobenzene Derivatives with Hydrazine: Leaving Group and Solvent Effects

“…This agrees with the rate determining formation of the zwitterionic intermediate I., Scheme 4. This is in line with the nucleophilic aromatic displacements of a good leaving group in polar and dipolar solvents (Khattab, Hamed, Albericio, & El-Faham, 2011;El-Mallah, Nabil, Senior, Ramadan, & Hamed, 2010;Asghar, Fathalla, & Hamed, 2009;Fathalla, Kassem, & Hamed, 2008;Khattab, Hassan, Hamed, & El-Faham, 2007;Al-Howsaway, Fathalla, El-Bardan, & Hamed, 2007;Fathalla & Hamed, 2006;Fathalla, Ibrahim, & Hamed, 2004;El-Hegazy, Abdel-Fathah, Hamed, & Sharaf, 2000;Hamed, El-Bardan, Saad, Gohar, & Hassan, 1997;Hamed, 1997aHamed, , 1997b. The plot of H # against log -S # for the reaction of 2 with hydrazine in MeOH, MeCN and DMSO gave straight line (r = 0.99) indicating a common mechanism for the reaction of 2 with hydrazine in these solvents.…”

Computational Study of Anomalous Reduction Potentials for Hydrogen Evolution Catalyzed by Cobalt Dithiolene Complexes

“…Experiments were carried out in a 1:1 (v:v) CH 3 CN:H 2 O solution, which has an experimental dielectric constant of ε o ≈ 50. 15 We used an average of 1/ε for acetonitrile and water to give ε o = 49 and ε ∞ = 1.79. Although the C-PCM method was not designed to treat mixed solvents, the qualitative trends are the same in pure water, pure acetonitrile, and mixed solvent, as indicated in SI.…”

Anilinolysis of Picryl Benzoate Derivatives in Methanol: Reactivity, Regioselectivity, Kinetics, and Mechanism

“…Aromatic nucleophilic substitution reactions have been proposed to proceed through an addition‐elimination mechanism (Ad‐E; S N Ar) involving the formation of Meisenheimer and zwitterionic complexes . As a matter of fact, previous mechanistic investigations have included examination of the effects of nucleophilic strength, solvation , leaving group ability, and reactivity of the substrates . There has been a discourse on whether the rate‐determining step is the addition of the nucleophile, elimination of the leaving group , proton transfer process , or whether it may switch depending on the solvent, nature of the nucleophile, the steric factor, as well as the degree of activation of the aromatic substrate, and the relative position of activating substitution(s) to the reaction center .…”