154853-46-0Relevant articles and documents
Nucleophilic Substitution Reactions of 2,4-Dinitrophenyl X-Substituted-Benzenesulfonates and Y-Substituted-Phenyl 4-Nitrobenzenesulfonates with Azide Ion: Regioselectivity and Reaction Mechanism
Moon, Ji-Hyun,Kim, Min-Young,Han, So-Yeop,Um, Ik-Hwan
, p. 1360 - 1365 (2015/07/15)
The second-order rate constants for reactions of 2,4-dinitrophenyl X-substituted-benzenesulfonates (4a-4f) and Y-substituted-phenyl-4-nitrobenzenesulfonates (5a-5f) with N3- ion have been measured spectrophotometrically. The reactions of 4a-4f proceed through S-O and C-O bond fission pathways competitively. Fraction of the S-O bond fission decreases rapidly as the substituent X in the benzenesulfonyl moiety changes from an electron-withdrawing group to an electron-donating group. The Hammett plots for reactions of 4a-4f are linear with ρX=1.87 and 0.56 for the S-O and C-O bond fission, respectively. The fact that the substituent X is further away from the reaction site of the C-O bond fission than that of the S-O bond fission is one reason for the smaller ρX value. The nature of the reaction mechanism (i.e., a stepwise mechanism in which expulsion of the leaving group occurs after the rate-determining step) is also responsible for the smaller ρX value obtained from the C-O bond fission. The Bronsted-type plot for the reactions of 5a-5f is linear with βlg=-0.63, which is typical for reactions reported previously to proceed through a concerted mechanism. Effects of substituents X and Y on regioselectivity and reaction mechanism are discussed in detail.
A kinetic study on nucleophilic displacement reactions of aryl benzenesulfonates with potassium ethoxide: Role of K+ ion and reaction mechanism deduced from analyses of LFERs and activation parameters
Um, Ik-Hwan,Kang, Ji-Sun,Shin, Young-Hee,Buncel, Erwin
, p. 490 - 497 (2013/03/13)
Pseudofirst-order rate constants (kobsd) have been measured spectrophotometrically for the nucleophilic substitution reactions of 2,4-dinitrophenyl X-substituted benzenesulfonates 4a-f and Y-substituted phenyl benzenesulfonates 5a-k with EtOK in anhydrous ethanol. Dissection of k obsd into kEtO- and kEtOK (i.e., the second-order rate constants for the reactions with the dissociated EtO - and ion-paired EtOK, respectively) shows that the ion-paired EtOK is more reactive than the dissociated EtO-, indicating that K + ion catalyzes the reaction. The catalytic effect exerted by K + ion (e.g., the kEtOK/kEtO- ratio) decreases linearly as the substituent X in the benzenesulfonyl moiety changes from an electron-donating group (EDG) to an electron-withdrawing group (EWG), but it is independent of the electronic nature of the substituent Y in the leaving group. The reactions have been concluded to proceed through a concerted mechanism from analyses of the kinetic data through linear free energy relationships (e.g., the Bronsted-type, Hammett, and Yukawa-Tsuno plots). K+ ion catalyzes the reactions by increasing the electrophilicity of the reaction center through a cyclic transition state (TS) rather than by increasing the nucleofugality of the leaving group. Activation parameters (e.g., ΔH? and ΔS?) determined from the reactions performed at five different temperatures further support the proposed mechanism and TS structures.
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.
