Effect of binary aqueous‐organic solvents on the reaction of phenacyl bromide with nitrobenzoic acid(s) in the presence of triethylamine

Abstract

Second-order rate constants (k 2 ) of the reaction between phenacyl bromide and equimolar mixture of nitrobenzoic acid(s)-triethylamine have been determined in dimethylformamide (DMF)/acetonitrile (ACN)/acetone and aqueous mixtures of these solvents by conductometric method at 30 • C. The rates of nitrobenzoic acids are found to be in the order: 4-NO 2 > 3-NO 2 > 3,5-(NO 2 ) 2 . Changes in the rate just by the addition of water (1% (v/v)) into organic component is rationalized. Decrease in the values of k 2 on increasing water content in organic solvent is explained on the basis of preferential solvation phenomenon. Single and dual regression analysis using the various solvent parameters of aqueous mixtures (E T (30), Z, π * , β, α, and Y) resulted in π * and α as the best parameters to explain solvation of nitrobenzoates. C

Kinetic investigation on the reactions of p‐toluenesulfonyl chloride with p‐substituted benzoic acid(s) in the presence of triethylamine in aprotic solvents

“…This may be explained on the basis of cross‐conjugation (Figs. 4a and 4b) 7,23. That is, −R parasubstituents (4‐NO 2 and 4‐Cl) may not fully exhibit −R effect, and it may also influence a small +R effect on the reaction center and vice versa in the case of +R parasubstituents (4‐OH, 4‐NH 2 , and 4‐OCH 3 ).…”

“…This can be explained on the basis of solvation. Triethylammonium benzoate ion may be desolvated more in ACN than in acetone due to the protogenic character of ACN 7,22. This may raise the energy of benzoate ion and diminish the energy gap between the reactants and TS, which increases the rate.…”

“…A number of kinetic investigations have been carried out on the nucleophilic substitution reactions involving metal carboxylates/triethylammonium carboxylates and active organic halide containing saturated carbon atom. The reactivity of metal carboxylates/triethylammonium carboxylates, the effect of solvents, formation of OC bond, and cleavage of CX bond in the transition state (TS), etc., have been discussed 1–7. Much work has not been done on the organic compounds containing S as a heteroatom like arenesulfonyl chloride, which is found to be a good substrate for nucleophilic substitution reactions 8–12.…”