Reactions of 2,4‐dinitrophenyl 5‐substituted‐2‐thiophenecarboxylate promoted by <scp>4‐ZC₆H₄O⁻</scp>/<scp>4‐ZC₆H₄OH</scp> in 20 mol% <scp>DMSO</scp>(aq). Effects of leaving group and nucleophile on the acyl transfer reactions

Abstract The kinetics of nucleophilic substitution reactions involving 2,4‐dinitrophenyl 5‐substituted‐2‐thiophenecarboxylate were studied kinetically with 4‐Z‐C 6 H 4 O − /4‐Z‐C OH, which facilitated the reactions, in 20 mol% DMSO(aq). followed second‐order and exhibited β acyl = −2.34 to −2.92, ρ (Y) 2.71–3.39, nuc 0.74–0.83, | lg 0.40–0.57. Based on interpretation results, we have concluded that reaction follows an addition–elimination mechanism first step is rate‐determining (rds). transition state structures for 4‐ZC ‐promoted remained nearly same a change leaving group from 4‐nitrophenoxide 2,4‐dinitrophenoxide. was similar R 2 NH‐promoted except former proceeded 1st being rds latter second stronger nucleophile.