Radiolysis solvent mixtures

In a novel kinetic approach, Dorfman et al. developed methods for rapidly generating very reactive carbanions such as the benzyl anion in solvent mixtures containing water and alcohols. With pulsed radiolysis techniques, they have been able to study the fast and very exothermic reactions of carbanions with these solvents. The studies have shown that despite the high exothermicity, the protonation is not diffusion controlled and depends on the nature of the carbanion s counterion. 

Pulse radiolysis reaction of iodide ions with a series of halogenated alkylperoxyl resulted in the oxidation of a total of three iodide ions. The rate constants were determined as a function of pH, polarity of solvent mixtures, and electronegativity of... 

Another example is the use of solvent mixtures to study protonation reactions. Thus, pulse radiolysis of acetone/2-propanol/carbon tetrachloride has been shown to produce HCl within approximately 100 ns, and this system has been used to measure rates of fast protonation reactions [43]. 

Similar observations were made in radiolytic experiments with N2O or N2-saturated 2-propanol solutions of [60]fullerene, despite the poor fullerene solubility. Radiolysis of N2O / 2-propanol solutions leads also to a single reactive species, namely, (CH3)2 C0H and the fullerene reduction proceeds similar to the one outlined in the toluene/2-propanol/acetone solvent mixture (13). In N2-saturated 2-propanol solutions the solvated electron (e soi), existing beside the (CH3)2 COH radical, reduces the [60]fullerene with a rate constant of 1.0 x 10 ° M s ... 

Irradiation of mixtures of cyclohexene with 1,3-cyclohexadiene leads to high yield of dimers (G = 6.3)86. Schutte and Freeman87 found that radiolysis of 1,3-cyclohexadiene dissolved in various solvents gives dimers mainly via cationic Diels-Alder addition,... 

Complexes with organic compounds have been reported. Solubility studies with tributyl phosphate (TBP) indicate the formation of a complex PoC14-2TBP (IS). Weighable amounts of polonium tetrachloride in dilute hydrochloric acid can be titrated to a colorless end point with ethylene-diamine tetra-acetic acid (EDTA) the results suggest a complex with two molecules of EDTA, but solubility studies favor a 1 1 complex. The EDTA complex is soluble in alkali and is more stable in alkaline than in acid media, but the ligand is rapidly destroyed by the radiation and solvent radiolysis products 12). However, EDTA can apparently be used to complex trace polonium in the separation of radium D-E-F mixtures (129). 

Examination of such degraded solvents is difficult from the analytical point of view. In multicomponent extractant-diluent/aqueous phase systems, free radicals are produced by radiolysis of major compounds water, acid, extractant, and diluent. These radicals, after dimerization or coupling with other compounds, are responsible for the formation of several families of compounds. For instance, in the PUREX process, the exposure of the solvent to radiolysis gives rise to a mixture of over 200 secondary products, most of them in trace quantities. 

Pulse radiolysis of 2-propanol has also been used to investigate elementary redox and radical reactions of fullerenes in solution [18]. For example, reduction of Ceo to C6o by Cs (k > 10 dm mol" s ) and (CH3)2 COH [k = (5 2) x 10 dm mor s ] was observed, and Ceo " was found to be stable for hours in the absence of oxygen. Ceo is insoluble in water, but its reduction in this solvent by (CH3)2 C0H was achieved by imbedding the fullerene in y-cyclodextrin to form a soluble guest-host complex in a 9 1 (vol %) water 2-propanol mixture. In this case, the reaction rate was two times slower than that in neat 2-propanol. Information was also obtained [18] on the addition of CH3 to Ceo in 2-propanol by the follow-... 

Reactions of the solvent with species in a feed mixture may also adversely affect an extraction system. Because of the radiation field from fission products in spent nuclear fuel, TBP reacts by radiolysis and acid hydrolysis to form dibutyl and monobutyl phosphoric acids (DBP and MBP, respectively). These latter species are also highly effective in extracting U and Pu, but at conditions... 

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