Preferential Solvation Effects on the Kinetics and Thermodynamics of Oxidation of Anilines by Chromium(VI)

Abstract

Summary The imidazolium fluorochromate (IFC) oxidation of fifteen meta - and para-substituted anilines, in varying mole fractions of benzene in 2-methylpropan-2-ol as mixtures, in the presence of p-toluenesulfonic acid (TsOH) is first order in IFC and TsOH and zero order in substrate. The various thermodynamic parameters for the oxidation have been reported and discussed. The validity of the isokinetic relationship and various linear free energy relationships have been tested and discussed. The activation free energy data failed to correlate with macroscopic solvent parameters such as εr and E T N. Correlation of Δ G # with Kamlet–Taft solvatochromic parameters (α, β and π*) suggests that the specific solute–solvent interactions play a major role in governing the reactivity.

Preferential solvational effects on the Cr(VI) oxidation of benzylamines in benzene/2‐methylpropan‐2‐ol mixtures

“…Since benzene is a more polarizable solvent (δ = 1) than 2-methylpropan-2-ol (δ = 0) [1], an increase in its mole fraction in the mixture increases the polarizability of the medium and consequently increased the rate of the oxidation. Parallel observations were recorded in the Cr(VI) oxidation of anilines in the binary mixture [5,8]. Figure 5 shows the solution FT-IR spectrum of the reaction mixture at different time intervals.…”

meso-TETRAPHENYLIRONPORPHYRIN(III) CHLORIDE CATALYZED OXIDATION OF ANILINE AND ITS SUBSTITUENTS BY m-CHLOROPERBENZOIC ACID

“…From the Eyrings equation 13 , the thermodynamic parameters enthalpy of activation and entropy of activation are figured out from the expression…”

“…6. The function of isokinetic relationship 15,16 reveals that a common mechanism is working in all the aniline oxidation reactions 13 . Isokinetic temperature is the temperature at which all the compounds react at same speed since this temperature variation of substituent has no influence on the free energy of activation.…”

“…So the obtained rate constants show deviation with substituents. Negative entropy of activation also gives the information that the complex formed is an associate type with a greater degree of charge in transition state than initial state 13 . The rate data obtained is also unsuccessful in proving that the typical Hammet equation logk obs vs σ is a dispersed gram and a sensitive plot (Fig.…”

“…This shows that the catalyst-aniline complex is likely to be the electrophile and free aniline may be the nucleophile. The influence of the substituents on the reactivity of the nucleophile is approximately compensated by the influence of the same substituent on the reactivity of the electrophile 13 . In some of the substituted aniline, exact compensation is doubtful and the resultant effect is experienced on the oxidation rate.…”