15481-55-7Relevant articles and documents
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
supporting information, 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.
Stoichiometric Solvation Effects. Part 2. A New Product-Rate Correlation for Solvolyses of p-Nitrobenzenesulfonyl Chloride in Alcohol-Water Mixtures
Bentley, T. William,Jones, Robert O.,Koo, In Sun
, p. 753 - 760 (2007/10/02)
For reactions involving nucleophilic attack in alcohol-water mixtures, a linear relationship between the reciprocal of product selectivities (S) and the molar ratios of alcohol and water solvents can be derived, if it is assumed that the reactions are second-order in protic solvent (e.g., with one molecule of solvent acting as a nucleophile and the other as a general base).The relationship (1/S = (slope)(/) + intercept) fits the products of solvolyses of p-nitrobenzenesulfonyl chloride in aqueous ethanol and methanol at 25 deg C (determined by refrigerated RP-HPLC) within the range from water to 80percent v/v alcohol-water.From the slopes and intercepts of these product plots and the one observed rate constant for hydrolysis in pure water, the observed first-order rate constants in alcohol-water mixtures up to 90percent (v/v) can be calculated satisfactority, further supporting the validity of the derived linear relationship; the kinetic model includes three thrid-order rate constants: kww, where water acts as both nucleophile and general base; kwa, water acts as a nucleophile and alcohol acts as a general base; kaw, alcohol acts as a nucleophile and water acts as a general base.Inclusion of a fourth rate-constant, kaa, where the alcohol acts as a nucleophile and a second molecule of alcohol acts as a general base, is necessary to account for solvolyses in 90-99percent alcohol-water; kaa can be calculated from the observed first-order rate constants in pure alcohols.Independent values of kaw and kwa can be obtained from kaa and the slopes and intercepts of linear relationships between S and the molar solvent ratio / within the range 90-99percent alcohol-water.The dominant effect of solvent stoichiometry and the absence of other substantial medium effects is confirmed by the approximately constant third-order rate constants, calculated from the observed first-order rate constants in acetonitrile-, acetone- and dioxane-water mixtures.
Reaction of Carboxylic Acid Esters with p-Toluenesulfonic Acid
Nitta, Yoshihiro,Arakawa, Yasushi
, p. 1380 - 1386 (2007/10/02)
The reaction of carboxylic acid esters with an excess of p-toluenesulfonic acid gave the corresponding p-toluenesulfonates.The mechanism of the transesterification is discussed.
