Ionic liquid radiolysis

Behar D, Neta P, Schultheisz C. (2002) Reaction kinetics in ionic liquids as studied by pulse radiolysis Redox reactions in the solvents methyltributylammo-nimn bis(trifluoromethylsulfonyl)imide and N-butylpyridiiun tetrafluoroborate. JPhys Chem A 106 3139-3147. 

Fig. 15. Benzophenone anion solvation observed at 800 nm in two ionic liquids by OFSS pulse radiolysis spectroscopy. The traces consist of three 1.5-ns OFSS segments.

Yang J, Kondoh T, Norizawa K, Nagaishi R, Tagushi M, Takahashi K, Rat oh R, Anishchik SV, Yoshida Y, Tagawa S. (2008) Picosecond pulse radiolysis Dynamics of solvated electrons in ionic liquid and geminate ion recombination in liquid alkanes. Radiat Phys Chem 77 1233-1238. 

James R Wishart received a B.S. in Chemistry from the Massachusetts Institute of Technology in 1979 and a Ph.D. in Inorganic Chemistry from Stanford University in 1985 under the direction of Prof Henry Taube. After a postdoctoral appointment at Rutgers University, in 1987 he joined the Brookhaven National Laboratory Chemistry Department as a Staff Scientist in the Radiation Chemistry Group. He founded and presently supervises the BNL Laser-Electron Accelerator Facility for picosecond electron pulse radiolysis. His research interests include ionic liquids, radiation chemistry, electron transfer, and new technology and techniques for pulse radiolysis. He has authored over 90 papers and chapters, and is the co-editor of Advances in Chemistry Series o. 254, Photoehemistry and Radiation Chemistry. 

Grodkowski, J. and Neta, R, Reaction kinetics in the ionic liquid methyltributyl ammonium bis(trifluoromethylsulfonyl)imide. Pulse radiolysis study of CF3 radical reactions, J. Phys. Chem. A106, 5468-5473 (2002). 

Both investigations also reported the pulse radiolysis of solutes dissolved in ionic liquids. Behar et al. studied the effect of the presence of Oj and CCI4 in [bmim][PF6] their results suggested that the latter was a more effective radical scavenger. They also looked at the formation of the radical cations of chlorpromazine (ClPz-+) andN,N,7 r, N -tetramethyl-p-phenylenediamine (TPMD- ) in the same solvent. Finally, the kinetics of oxidation of ClPz in [bmim][PF( ] were studied. The experimentally determined bimolecular rate constant values were corrected for the high viscosity of the ionic liquid by estimation of the values of the diffusion-controlled rate constant, using Equation (5.3),... 

Behar, D., Gonzalez, C. Neta, P. (2001). Reaction Kinetics in Ionic Liquids Pulse Radiolysis Studies of l-Butyl-3-methylimidazolium Salts,. Phys. Ghent. A105 7607-7614. 

The kinetics data of the geminate ion recombination in irradiated liquid hydrocarbons obtained by the subpicosecond pulse radiolysis was analyzed by Monte Carlo simulation based on the diffusion in an electric field [77,81,82], The simulation data were convoluted by the response function and fitted to the experimental data. By transforming the time-dependent behavior of cation radicals to the distribution function of cation radical-electron distance, the time-dependent distribution was obtained. Subsequently, the relationship between the space resolution and the space distribution of ionic species was discussed. The space distribution of reactive intermediates produced by radiation is very important for advanced science and technology using ionizing radiation such as nanolithography and nanotechnology [77,82]. 

It seems to the present authors that the above-mentioned scheme of the initiation process in the glass matrices can be extended, at least, to the radiation-induced ionic polymerizations in liquid solutions at higher temperatures. This will be verified by rapid techniques of measurement, such as the pulse radiolysis method. 

The metals, and to a lesser extent Ca, Sr, Ba, Eu, and Yb, are soluble in liquid ammonia and certain other solvents, giving solutions that are blue when dilute. These solutions conduct electricity electrolytically and measurements of transport numbers suggest that the main current carrier, which has an extraordinarily high mobility, is the solvated electron. Solvated electrons are also formed in aqueous or other polar media by photolysis, radiolysis with ionizing radiations such as X rays, electrolysis, and probably some chemical reactions. The high reactivity of the electron and its short lifetime (in 0.75 M HC104, 6 x 10"11 s in neutral water, tm ca. 10-4 s) make detection of such low concentrations difficult. Electrons can also be trapped in ionic lattices or in frozen water or alcohol when irradiated and again blue colors are observed. In very pure liquid ammonia, the lifetime of the... 

The rare-gas sensitized radiolysis of propane has been studied in the gas phase and in the liquid phase". Charge transfer from the rare-gas ion to propane is followed by ionic reactions. In particular, the decomposition of C3H8 to give CH4 by reaction (4) is important, as is the ion-molecule reaction of C2H5 with propane to give ethane by reaction (7). 

A recent study using a pulse-radiolysis technique on liquid benzene solutions has shown that there is an abundant yield of excited singlet ( B2 ) and triplet ( B) states of benzene. The effect of ionic scavengers in this study shows that ions are precursors of both singlet and triplet states. It is concluded that the excited states arise from ion-electron recombination. This recombination is particularly facile in benzene solution owing to the numerous excited states of low energy in benzene, which rapidly thermalize the electrons. The formation of excited species which are relatively unreactive, as implied by the observation of fluorescence from these states, may account for the low (7-value of benzene decomposition in the liquid phase. 

Tladiation chemists have been aware for about 15 years that the presence of dilute solutes in liquid hydrocarbons can change the course of radiation chemical reactions by other than the normally expected secondary radical reactions. For example, Manion and Burton (40) in early work on the radiolysis of benzene-cyclohexane solutions, drew attention to the possibility of energy transfer from solvent to solute. Furthermore, it is known that in hydrocarbon solvents certain solutes are capable of capturing electrons, thus interfering with the normal ion-recombination process (14, 20, 65, 72). Though ionic products can be observed readily in hydrocarbon glasses [e.g., (19, 21)] demonstration of effects which can be specifically ascribed to electron capture in the liquid state has been elusive until recently. Reaction of positive ions prior to neutralization can play an important role as demonstrated recently by studies on... 

In liquid hydrocarbon radiolysis, analogies are frequently drawn from gas-phase studies, particularly in regard to ionic processes. We... 

Benzene, toluene, ethylbenzene, and the three xylenes have been irradiated in the vapor phase with gamma rays. Products and yields have been compared with those in liquid-phase radiolysis. G values for disappearance in the vapor phase range from 6 to 10, more than five times greater than in the liquid phase. The principal product in each case is polymer. All of the identified products are also found in the liquid phase, but relative yields are markedly different. The high yields of acetylene and some other products in the vapor phase suggest that ionic processes are more important here than in the liquid phase. 

The isomerization of o-xylene in liquid-phase radiolysis, as well as in vapor-phase photolysis either at 2537 A. (17) or in the vacuum ultraviolet (13), gives a very high ratio of meta to para isomer. The more nearly statistical distribution of isomers observed in the vapor-phase radiolysis may again be rationalized in terms of an ionic process. Mass spectral studies (4) of isotopically labeled p-xylene indicate extensive randomization of carbon atoms in the abundant C8H9+ ion. It is not known whether such randomization ocurs in the parent ion or whether randomized ions could revert to xylenes, but the rearomatization of a randomized species has been demonstrated (19) in the radiolysis of toluene-7-14C vapor. 

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