Enthalpy and entropy relations in reactions of 2,4-dinitrophenyl benzoate with phenols in the presence of potassium carbonate in dimethylformamide

Enthalpy-entropy correlations in reactions of 2,4-dinitrophenyl benzoate with phenols in the presence of potassium hydrogen carbonate and with potassium phenoxides in dimethylformamide

“…Table 4 also contains previously reported data for the reaction of compound I with phenols IIa-IIh in the presence of potassium carbonate [9], as well as the data for the reactions of carbonyl compounds with anilines and pyridines in aprotic solvents [18][19][20][21][22][23]. In addition, the compensation temperatures T comp = δΔH ≠ /δΔS ≠ are given, which characterize the structure of transition state for reactions with the same mechanism [14].…”

“…The resulting esters IV do not undergo transesterification, which especially emphasizes advantages in using KHCO 3 as a weaker base than K 2 CO 3 (cf. [9]). …”

“…Transesterification of substituted 4-nitrophenyl benzoates by the action of 4-chlorophenol-K 2 CO 3 complex in DMF under heterogeneous conditions involves formation of tetrahedral intermediate as rate-determining step [8]. However, the reaction of 2,4-dinitrophenyl benzoate DOI: 10 with potassium carbonate complexes of phenols in DMF follows A N + D N mechanism where the second step is rate-determining [9]. It was presumed that the rate-determining step is elimination of 2,4-dinitrophenoxy group, for the preceding step (nucleophilic attack) implies proton transfer [9].…”

“…However, the reaction of 2,4-dinitrophenyl benzoate DOI: 10 with potassium carbonate complexes of phenols in DMF follows A N + D N mechanism where the second step is rate-determining [9]. It was presumed that the rate-determining step is elimination of 2,4-dinitrophenoxy group, for the preceding step (nucleophilic attack) implies proton transfer [9]. The goal of the present work was to study transesterification of 2,4-dinitrophenyl benzoate by the action of phenols RC 6 H 4 OH in the presence of potassium hydrogen carbonate (which is a weaker base than potassium carbonate) and of the corresponding potassium phenoxides RC 6 H 4 O -K + in DMF.…”

“…As we showed previously, an appropriate procedure for studying the effect of nucleophile structure on the rate of transesterification under both homogeneous (ArO -K + ) and heterogeneous conditions (ArOH-K 2 CO 3 ) is based on competitive reactions [8,9]. In such a way we obtained temperature dependences of the relative rate constants for the reactions of 2,4-dinitrophenyl benzoate (I) in DMF with phenols IIa-IIh in the presence of potassium hydrogen carbonate and with potassium phenoxides IIIa-IIIh (Scheme 1).…”