Kinetic studies of bold σ -adduct formation and nucleophilic substitution in the reactions of ethyl 2,4,6-trinitrophenyl ether, some phenyl 2,4,6-trinitrophenyl ethers, and phenyl 2,4-dinitronaphthyl ether with aniline in dimethyl sulfoxide

Experimental and theoretical approaches to the study of the reactivity and mechanism of the substitution of phenyl 1‐(2,4‐dinitronaphthyl) ether with anilines derivatives

“…Also, Table 2 reveals that the values of ρ N increase with the decrease in temperature ( ρ N ∝ 1/ T ) as reported in the literature 49,52 . The similarity is explicable if the transition state developed in the rate‐determining step for the reactions of phenyl 1‐(2,4‐dinitronaphthyl) ether ( 1 ) with substituted anilines ( 2a‐f ) approximated to that of the zwitterion intermediate ( I ) formed in the titled reaction where the conjugation of the amino group with the benzene ring is destroyed, as in the formation of anilinium ions 32 . Other workers suggested that the ρ values are due to the particular nature of the substrate 48 …”

“…All the plots of k obs for the titled anilinolysis reaction versus the square of the concentration of aniline derivatives ( 2a‐f ) ([aniline] 2 ) gave straight lines with a negligible intercept, or the square of the amine concentration shows intercepts on the y axis, which was likely to indicate that there was some reaction flux from the uncatalyzed decomposition of the zwitterion intermediate, suggesting an amine‐catalyzed reaction (Table 1 and Figure 1). This indicated that the reaction was catalyzed by a second aniline molecule where either proton transfer or removal of the phenoxy group was a rate‐determining step 32 …”

“…Two possible catalyzed pathways are known: First, the zwitterion intermediate ( I ) undergoes deprotonation to form the Meisenheimer intermediate ( II ) in the rate‐determining step and rapid removal of the leaving group (rate‐limiting proton transfer, RLPT, mechanism). Second, the zwitterion intermediate ( I ) undergoes fast proton transfer with the slow loss of the phenoxide ion k 4 , resulting in the reintroduction of the aromaticity to give aryl 1‐(2,4‐dinitronaphthyl) amine ( 3a‐f ), that is, the specific base‐general acid (SB‐GA) catalysis 32 …”

“…This indicated that the reaction was catalyzed by a second aniline molecule where either proton transfer or removal of the phenoxy group was a ratedetermining step. 32…”

“…Second, the zwitterion intermediate (I) undergoes fast proton transfer with the slow loss of the phenoxide ion k 4 , resulting in the reintroduction of the aromaticity to give aryl 1-(2,4-dinitronaphthyl) amine (3a-f), that is, the specific basegeneral acid (SB-GA) catalysis. 32 The effect of the external base, as pyridine or p-toluidinium hydrochloride as conjugate acid, on the rate constant is studied to examine the rate-limiting step in the catalyzed process. It is found that the catalysis by the external base is pronounced (SB mechanism), where a change in the thirdorder rate constant by the addition of external base pyridine is observed, whereas the presence of the conjugate anilinium ion showed a negligible change in rate constants ( Table 2).…”