69173-73-5Relevant articles and documents
Kinetic study on nucleophilic substitution reactions of aryl diphenylphosphinates with butane-2,3-dione monoximate and aryloxide anions: Reaction mechanism and origin of the α-effect
Um, Ik-Hwan,Han, Jeong-Yoon
, p. 1180 - 1184 (2016/08/12)
A kinetic study is reported for nucleophilic substitution reactions of X-substituted-phenyl diphenylphosphinates (3a-3f) with butane-2,3-dione monoximate (Ox-) and a series of Y-substituted-phenoxide (Y-PhO-) ions in 50 mol % H2O/50 mol % DMSO at 25.0 ± 0.1°C. The reactions of 3a-3f with Ox- and 4-chlorophenoxide (4-ClPhO-) result in linear Br?nsted-type plots with βlg = -0.70 and -0.64, respectively, a typical βlg value for reactions reported previously to proceed through a concerted mechanism. The Br?nsted-type plots for the reactions of 4-chloro-2-nitrophenyl diphenylphosphinate (3a), 4-nitrophenyl diphenylphosphinate (3b), and 4-acetylphenyl diphenylphosphinate (3d) with Y-PhO- are also linear with βnuc = 0.15-0.35. The current reactions have been concluded to proceed through a concerted mechanism in which the bond formation is much less advanced than the bond rupture in the TS on the basis of the βlg and βnuc values. The α-effect observed in this study is very small (i.e., the kOx-/kp-ClPhO- ratio=4.61-43.5) and is independent of the leaving-group basicity. It has been concluded that the α-effect shown by Ox- in the current reactions is mainly due to desolvation of Ox- in the reaction medium (ground-state contribution) rather than stabilization of the transition-state (TS contribution) on the basis of the kinetic results.
Dependence of Transition-state Structure on Nucleophile in the Reaction of Aryl Oxide Anions with Aryl Diphenylphosphate Esters
Ba-Saif, Salem A.,Waring, Mark A.,Williams, Andrew
, p. 1653 - 1659 (2007/10/02)
Second-order rate constants have been measured for reaction of aryl oxide anions with substituted phenyl diphenylphosphate esters in aqueous media at 25 deg C.The rate constants obey good Broensted type correlations with the pKa of either the leaving group or nucleophile.Both βnuc and βlg values vary substantially with basicity of leaving group and nucleophile, respectively, providing evidence for coupling between bond fission and formation.Attack of phenolate ions on 2,4-dinitrophenyl diphenylphosphate has a βnuc value of 0.12 giving a Kreevoy's tightness parameter value, τ, of 0.18 which is consistent with an 'exploded' transition state for the identity reaction involving 2,4-dinitrophenolate ion as the nucleophile.Transfer of the diphenylphosphinoyl group between 2,4-dinitrophenolate ion nucleophiles has a τ value of 0.28, consistent with an 'exploded' transition state for this reaction also.The identity reaction involving transfer of the diphenylphosphoryl group between phenolates ions has a τ value of 1.20, indicating an almost synchronous process.The data for transfer of the diphenylphosphinoyl and diethylphosphoryl groups between phenolate ion nucleophiles indicates that the identity reaction for the parent phenol has an almost synchronous mechanism for the former phosphinoyl species (τ = 0.92) whereas the latter (τ = 1.45) is almost associative.
Concerted Acetyl Group Transfer between Substituted Phenolate Ion Nucleophiles: Variation of Transition-State Structure as a Function of Substituent
Ba-Saif, Salem,Luthra, Ajay K.,Williams, Andrew
, p. 2647 - 2652 (2007/10/02)
Second-order rate constants (kArO) have been measured for the concerted displacement of aryl oxide from aryl acetates in aqueous solution by substituted phenoxide ions.Values of kArO obey linear Bronsted correlations when either the leaving group or the attacking phenolate ion structures are varied.The Bronsted coefficients obey the equations βnuc = 0.20pK1g - 0.68 and β1g = 0.15pKnuc - 1.73 to a good degree of precision, and the variation indicates that the structure of the transition-state changes within the range of phenolate ions studied; this alsoprovides confirmation that a concerted mechanism operates.The equations for βnuc and β1g predict the equation (log kii = 0.17pKa2 - 2.41pKa + C) for kii, the rate constant for the reaction of aryl oxide ion with acetates bearing identical aryl oxide leaving groups.The identity rate constants may be interpolated from the observed rate constants (kArO) and exhibit excellent fit to the above equation with the single disposable parameter, C, set at 6.5.This is the first report of curvature in a Bronsted plot of identity rate constants.Effective charge development and loss on leaving and attacking oxyanions is fully balanced in the transition state when entering and leaving nucleophiles have a pKa of 7.1.Tetrahedral or acylium ion-like transition-state structures are predicted for hypothetical phenols with pKa's of 11.7 and 2.0, respectively.
