Medium effect on the α-effect for nucleophilic substitution reactions of p-nitrophenyl acetate with benzohydroxamates and m-chlorophenoxide in DMSO–H₂O mixtures as contrasts with MeCN–H₂O mixtures: comparing two very different polar aprotic solvent components

How the Nature of an Alpha-Nucleophile Determines a Brønsted Type-Plot and Its Reaction Pathways. An Experimental Study

“…Then, hydrogen-bonding interactions of the media (solvent as acceptor with β parameter) with positive charge on the activated complex of the reaction will stabilize the activated complex better than the reactants; therefore, increasing the β parameter accelerates the reaction rate (Kamlet et al, 1983) Accordingly, heterocyclic substrates that contains nitrogen atoms in its chemical structure assist a favorable nucleophilic attack by high nucleophilic amines, but slow LG departures. On this way, the nature of the reacting pair and the reaction media drastically affects the nucleophilic reaction rates and the RDS on the reaction mechanism (Klopman and Frierson, 1984;Garver et al, 2011;Gazitúa et al, 2018;Um et al, 2018) Finally, in order to determine the HB effect, it was carried out the kinetic study of phenyl hydrazine (see Supplementary Tables S37-S39 and Supplementary Figure S13 in SM) with the same substrate. Note that, this nucleophile with a potential alpha-effect showed a similar behaviour than aniline derivatives (k N 1.45 ± 0.006 M −1 s −1 and pK a 5.25 versus k N 0.99 ± 0.0139 M −1 s −1 and pK a 4.73, respectively) reinforcing the substituent effect exerted over the nucleophilic center.…”