Separation photochemical techniques

DePoorter, G. L. Rofer-DePoorter, C. K. Application of Photochemical Techniques to Actinide Separation Processes , Preceding paper in this symposium. 

Application of Photochemical Techniques to Actinide Separation Processes... 

Photochemical separation, with the new capabilities of lasers as light sources, provides many new areas of investigation. Application of photochemical techniques to actinide separations alone has an enormous potential. As lasers become more reliable and economical, photochemical separation should become an attractive technique for many systems. 

Indeed, time-resolved resonance Raman (TR ) spectroscopy has been successfully employed to study the structure and dynamics of many short-lived molecular species and is the topic of a separate chapter by D. L. Phillips in this book. Like TR spectroscopy, TRIR spectroscopy gives one the ability to monitor directly both the structure and dynamics of the reactants, intermediates, and products of photochemical reactions. The time-resolved Raman and IR experiments, along with their transient UV-VIS absorption predecessor, are of course all complementary, and a combination of these techniques can give a very detailed picture of a photochemical reaction. 

Chen, Y.-W., et al. 2005. Photochemical behavior of inorganic and organic selenium compounds in various aqueous solutions. Analytica Chi mica Acta, 545(2), 142-148. Chester, R. Hughes, M.J. 1967. A chemical technique for the separation of ferromanganese minerals, carbonate minerals... 

In hexacyanochromate (III) ion, the lowest doublet and quartet ex- ited states are well separated (Section 8.6). By the use of suitable sensitizers, it is possible to excite the two states separately. By such techniques, it has been established that photoaquation of cyanide ion occurs from the excited quartet state 4T , whereas E state is photochemically inactive and the seat of phosphorescence emission. The intersystem quartet to doublet crossing is not always fast. 

This methodology was applied to the synthesis of L-streptose [91] and methyl a-D-mycaroside [95 a], The difficulty of this photochemical oxidation originates from the sensitivity of pyruvates to hydrolysis. This approach seems limited to small quantities of substrates but does not need any separation technique as in oxidation by pyridinium chlorochromate [95 b]. Nethertheless, photolysis of pyruvates of partially protected derivatives of a-D-g/ucofuranose and P-D-fructofuranose in benzene yields the corresponding oxidized products in excellent yields [96]. 

The preparative potential of the photochemical reactions of Mn2(CO)10 and Re2(CO)10 with conjugated dienes has hitherto been used only rarely (51,147,166-168). The reason for this might be that the reactions do not proceed in a simple fashion. Normally, mixtures of several products are obtained. Powerful separation techniques such as low-temperature column chromatography or high-performance liquid (HPL) chromatography are necessary to isolate the products, and this has thrown some light on the nature of the reactions. 

---