The reactions of diethyl 4-nitrophenyl phosphate (1) with a series of nucleophiles: phenoxides, secondary alicyclic (SA) amines, and pyridines are subjected to a kinetic study. Under excess of nucleophile, all the reactions obey pseudo-first-order kinetics and are first order in the nucleophile. The nucleophilic rate constants (k N ) obtained are pH independent for all the reactions studied. The Brønsted-type plot (log k N vs. pK a nucleophile) obtained for the phenolysis is linear with slope β = 0.21; no break was found at pK a 7.5, consistent with a concerted mechanism. The Brønsted-type plots for the SA aminolysis and pyridinolysis are linear with slopes β = 0.39 and 0.43, respectively, also suggesting concerted processes. The concerted mechanisms for the latter reactions are proposed on the basis of the lack of break in the Brønsted-type plots and the instability of the hypothetical pentacoordinate intermediates formed in these reactions. C 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: [708][709][710][711][712][713][714] 2011

An electrochemical technique was used to investigate pKa values of some substituted secondary alicyclic (SA) amines, pyridines (py), anilines (AN), and triethylamine (Et3N) in different ionic liquids. The method involves cyclic voltammetry at a platinized Pt electrode. The experimental data were correlated with pKa values reported previously in aqueous solution, and Hammett parameters were correlated with pKa values in ionic liquids to determine ρ values in these media.

The synthesis of a series of ionic liquids using 1-butyl 3-methylimidazolium (Bmim+) as a cation and different amino acids (AA) as anions (Bmim[AA]) is described. These ILs were used for the first time as reaction media to achieve more eco-friendly Paraoxon degradation. The results show that the degradation of Paraoxon in these Bmim[AA]s is accomplished with great efficiency and without an extra nucleophilic agent. Therefore, we propose that all the Bmim[AA]s used in this study have a dual role in the outcome of this reaction; as a nucleophile and a solvent to carry out degradation of the organophosphorous pesticide, Paraoxon. Both kinetics and product distribution results found in this study for Paraoxon degradation turned out to be promising, because this process is achieved in a reaction medium with a better environmental profile.

The reactions of O,O-diethyl 2,4-dinitrophenyl phosphate triester (1) with secondary alicyclic (SA) amines in the ionic liquids [Bmim]BF4 and [Bmim]DCA were subjected to a kinetic study. Eyring plots were obtained for the title reactions in the above ionic liquids (ILs) and also in aqueous ethanol (44 wt% ethanol). Two different reaction pathways were observed in [Bmim]BF4: nucleophilic attack at the phosphoryl center, SN2(P), and at the C-1 aromatic carbon, SN(Ar), where the product distribution remained constant and independent of the amine nature. In contrast, in [Bmim]DCA only the SN2(P) pathway was found. From the kinetic analysis of the SN2(P) pathway in both ILs, curved upwards plots of kobsdvs. 1-formylpiperazine concentration were obtained. Based on the kinetic behavior, a change in the mechanism of the SN2(P) pathway is proposed for the aminolysis of 1, from a concerted process in aqueous ethanol to a stepwise mechanism, through a zwitterionic pentacoordinate intermediate, when [Bmim]BF4 and [Bmim]DCA are used as the solvents of the reaction.

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