45934-90-5Relevant academic research and scientific papers
Regioselectivity and the nature of the reaction mechanism in nucleophilic substitution reactions of 2,4-dinitrophenyl X-substituted benzenesulfonates with primary amines
Um, Ik-Hwan,Hong, Jin-Young,Kim, Jung-Joo,Chae, Ok-Mi,Bae, Sun-Kun
, p. 5180 - 5185 (2007/10/03)
Second-order rate constants have been measured for the reaction of 2,4-dinitrophenyl X-substituted benzenesulfonates with a series of primary amines. The nucleophilic substitution reaction proceeds through competitive S-O and C-O bond fission pathways. The S-O bond fission occurs dominantly for reactions with highly basic amines or with substrates having a strong electron-withdrawing group in the sulfonyl moiety. On the other hand, the C-O bond fission occurs considerably for the reactions with low basic amines or with substrates having a strong electron-donating group in the sulfonyl moiety, emphasizing that the regioselectivity is governed by both the amine basicity and the electronic effect of the sulfonyl substituent X. The apparent second-order rate constants for the S-O bond fission have resulted in a nonlinear Bronsted-type plot for the reaction of 2,4-dinitrophenyl benzenesulfonate with 10 different primary amines, suggesting that a change in the rate-determining step occurs upon changing the amine basicity. The microscopic rate constants (k1 and k2/k-1 ratio) associated with the S-O bond fission pathway support the proposed mechanism. The second-order rate constants for the S-O bond fission result in good linear Yukawa-Tsuno plots for the aminolyses of 2,4-dinitrophenyl X-substituted benzenesulfonates. However, the second-order rate constants for the C-O bond fission show no correlation with the electronic nature of the sulfonyl substituent X, indicating that the C-O bond fission proceeds through an SNAR mechanism in which the leaving group departure occurs rapidly after the rate-determining step.
The Hammett equation applied to the nucleophilic displacement of ions and ion pairs on substituted benzenesulphonates
Alunni, Sergio,Pica, Monica,Reichenbach, Gustavo
, p. 265 - 270 (2007/10/03)
Nucleophilic substitution on meta- and para-substituted methyl benzenesulphonates was studied with two chloride salts with different structures: NBu4Cl or KCl-Kryptofix 2,2,2. Treating the results with the Acree equation shows that the reaction proceeds by two reaction paths, one involving the chloride ion and the other, slower one, involving the ion pairs. Treating the results with the Hammett equation gives consistent data, and shows that ρ is positive and nearly the same for the two reaction paths (ρ ≈ +2). The reactivity of methyl p-nitrobenzenesulphonate was compared with that of the corresponding ethyl derivative, and it is shown that the methyl derivative reacts faster than the ethyl derivative in both paths. The results are interpreted based on the assumption that in both paths a negative charge is developed on the leaving group in the transition state, and that the activated complex is linear. Copyright
The Hammett equation and micellar effects on SN2 reactions of methyl benzenesulfonates - The role of micellar polarity
Brinchi, Lucia,Di Profio, Pietro,Germani, Raimondo,Savelli, Gianfranco,Spreti, Nicoletta,Bunton, Clifford A.
, p. 3849 - 3854 (2007/10/03)
Substituent effects on the reaction of H2O, OH-, and Br- with p-substituted methyl benzenesulfonates in cationic micelles of cetyl trialkylammonium ion surfactants (n-C16H33NR3X, X = OH, Br, R = Me, Et, nPr, nBu) and in water were analyzed by using the Hammett equation. Values of p in the various media confirm that micellar interfacial regions are less polar than water and polarities decrease with increasing bulk of the surfactant head-group. Wiley-VCH Verlag GmbH, 2000.
