Transition-State Variation in the Nucleophilic Substitution Reactions of Aryl Bis(4-methoxyphenyl) Phosphates with Pyridines in Acetonitrile
作者:Hai Whang Lee、Arun Kanti Guha、Chang Kon Kim、Ikchoon Lee
DOI:10.1021/jo0162742
日期:2002.4.1
The kinetics and mechanism of the reactions of Z-aryl bis(4-methoxyphenyl) phosphates, (4-MeOC(6)H(4)O)(2)P(=O)OC(6)H(4)Z, with pyridines (XC(5)H(4)N) are investigated in acetonitrile at 55.0 degrees C. In the case of more basic phenolate leaving groups (Z = 4-Cl, 3-CN), the magnitudes of beta(X) (beta(nuc)) and beta(Z) (beta(lg)) indicate that mechanism changes from a concerted process (beta(X) =
Electrochemistry of Electron-Transfer Probes. The Role of the Leaving Group in the Cleavage of Radical Anions of α-Aryloxyacetophenones<sup>1</sup>
作者:Mogens L. Andersen、N. Mathivanan、Danial D. M. Wayner
DOI:10.1021/ja954093+
日期:1996.1.1
potential (E°) of α-phenoxyacetophenone has been determined from the voltammetric peak potential obtained by linear sweep voltammetry in combination with the rate constant for fragmentation of the radicalanion which had been determined by laser flash photolysis. The E° values of a number of α-aryloxyacetophenones were then estimated from a correlation of the 13C chemical shifts of the carbonyl carbon
El Seoud, Omar A.; Ruasse, Marie-Francoise; Rodrigues, Wagner A., Journal of the Chemical Society. Perkin Transactions 2 (2001), 2002, # 6, p. 1053 - 1058
作者:El Seoud, Omar A.、Ruasse, Marie-Francoise、Rodrigues, Wagner A.
DOI:——
日期:——
Electrochemistry of Electron Transfer Probes. alpha-Aryloxyacetoveratrones and Implications for the Mechanism of Photo-yellowing of Pulp.
作者:Mogens L. Andersen、Danial D. M. Wayner、Yves Dory、Jean Marc Chapuzet、Jean Lessard、André Tallec、Tatsuya Shono、H. Toftlund
DOI:10.3891/acta.chem.scand.53-0830
日期:——
Standard potentials (E degrees) of a series of substituted alpha-aryloxyacetoveratrone derivatives have been determined from a correlation of the C-13 NMR chemical shifts of the carbonyl group and a similar correlation (E degrees vs. C-13 NMR shifts) within a series of alpha-anilinoacetoveratrones. Using these potentials the rate constants for fragmentation of the radical anions were determined by digital simulation of the voltammetric waves. The rate contants for C-O cleavage in the radical anions correlate with the pK(a) of the corresponding phenols. The fragmentations are all in the activated region of a general free energy relationship for this class of compound (alpha=0.5). The standard potential and rate constant for fragmention of the alpha-guaiacoxyacetoveratrone radical anion also were determined. This species is a model compound for one of the lignin substructures. The implication of these results on the currently accepted mechanism for photoyellowing of lignin rich paper is discussed.
Kinetics and Mechanistic Study of the Reaction of Cyclic Anhydrides with Substituted Phenols. Structure−Reactivity Relationships
作者:Gabriel O. Andrés、Rita H. de Rossi
DOI:10.1021/jo048183l
日期:2005.2.1
maleic anhydrides with different substituted phenols (Z-PhOH with Z = H, m-CH3, p-CH3, m-Cl, p-Cl, and m-CN) were studied in aqueous solution. Two kinetic processes well separated in time were observed. The fast one is attributed to the formation of the aryl ester in equilibrium with the anhydride and allows the determination of the rate of nucleophilic attack of the phenol on the anhydride (k-A).