Anion partitioning

The mechanism for the generation of quinone methide 58 by reductive elimination of 55 has been investigated.106 Single-electron reduction by 55 by pulse radiolysis in water gives the semiquinone radical anion 56, whose decay was monitored by transient absorption spectroscopy. This radical anion partitions between disproportionation to 60 and elimination to form the radical 58. Disproportionation dominates at pH 7, but as the pH is lowered to 3 the competing elimination reaction to form the quinone methide radical 58 is observed for X = -OMe and -OPh. It was proposed that the product yields are controlled by the position of the equilibrium for protonation of 56 and that 56 undergoes mainly disproportionation, while the semiquinone radical 57 - undergoes mainly elimination of HX (Scheme 28). The quinone methide 59 is then formed by the one-electron reduction of 58. 

Organotin-Mediated Anion Partitioning into Liquid Polymeric Membranes... 

Some of these questions were clarified by studying the potential dependence of the ET rate at the ITIES using SECM. The potential drop across the ITIES (A°wpotential-determining ions in the two liquid phases. If only one type of ion (e.g., CIO4 anion) partitions between two solvents ... 

Rogers et al. [8,23,32,41,51 showed that the pertechnetate anion partitions quantitatively to the PEG-rich phase in a variety of PEG-ABSs. The partitioning behavior of this ion is affected by the numerous variables which affect system composition in an ABS identity of the cation or anion in the phase-forming salt, salt concentration, type and molecular weight of the polymer, polymer concentration, temperature, pH, and the presence of other matrix ions in the ABS. 

Original data were obtained as sodium salt partition constants (log/C,. ) but had been reported as the individual anion partition constants via the relation logATi(A ) = ogKi - log/CdNa" ), where log/Cj(Na ) = -6.0 (TATB assumption). 

Table 6. Anion partition coefficients at the air-water interface.

Levitskaia, T.G. Maya, L. van Berkel, G.J. Moyer, B. A. (2007) Anion Partitioning and Ion-Pairing Behavior of Anions in the Extraction of Cesium Salts by 4,5"-Bis(ferf-octylbenzo)dibenzo-24-crown-8 in 1,2-Dichloroethane, Inorg. Chem., 46 261-272. 

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