Radiolytic chlorides

In conclusion, despite their protective effect as regards degradation, the use of aromatic diluents has been avoided because of their low flash point. The classical diluents selected for PUREX process operations were hydrocarbons, either pure compounds (i.e., n-dodecane), or mixtures of different products (i.e., hydrogenated polypropylene tetramer, odorless kerosene, etc.) (93). Halocarbon diluents had two major drawbacks linked to their radiolytic behavior sensitization of TBP degradation and the production of extremely corrosive chloride ions (89, 93, 95). 

Unambiguous evidence was provided for a relatively long-lived electron adduct to methylsulfonyl chloride formed in reaction (47) k J = (3.3 0.3) X 10 ° M s and involving pulse radiolytically generated hydrated electron ... 

In the Pt-doped hexagonal mesophase formed from CPCI (cetyl pyridinium chloride), platinum ions are adsorbed at the surface of the surfactant cylinders. They are reduced radiolytically into a metal layer as a nanotube of around 10 nm diameter and a few hundred nm long (Fig. 3f). Extraction of all these nanostructures is achieved by dissolution of the soft template using alcohol. This possible easy extraction constitutes a marked advantage over the synthesis in hard templates, such as mesoporous silica or carbon nanotubes, the dissolution of which is more hazardous for the metal nanostructures. 

Several recent publications indicate that the role of intermediate complexes in ionic reactions is still controversial (21, 24, 25). Our interest in this and earlier observations of persistent complexes in alkyl halides already mentioned prompted us to study ionic reactions in ethyl chloride. The previously noted mass spectrometric investigations of alkyl halides did not include the chlorides, and radiolytic studies of these compounds have been limited to the propyl and butyl chlorides which apparently isomerize (39). The present investigation consists of two phases. In the initial phase, the ion-molecule reactions for ethyl chloride were probed by the sensitive mass spectrometric methods which we have applied in recent studies of a similar nature (3,12, 28, 43). In the latter part of this study, the gas-phase radiolysis and vacuum-ultraviolet photolysis of ethyl chloride have been studied to identify those products which arise from ionic precursors. More specifically, we wished to define the behavior under radiolytic conditions of those intermediate ionic species which the spectrometric studies suggested were important, and we hoped to arrive at a reasonable conciliation of the ionic reaction information derived from these different but complementary techniques. 

Implications of Mass Spectrometric Data for Radiation Chemistry. Apart from the positive identification of the ion-molecule reactions in ethyl chloride, the most significant observation from the mass spectrometric studies which has direct application to the radiolysis of this compound is the fact that at pressures greater than ca. 100 /a, essentially the only stable ion in this system is C4Hi0C1+. Therefore, the neutralization of ions as a potential contributor to radiolysis products will be important only for this ion. Moreover, this will hold true even if there are variations in the extent of primary fragmentation with increasing pressure. The radiolysis studies which will now be described assess the contribution of ionic processes to radiolytic yields and provide some indications as to the mode of neutralization of the stable ionic species in the ethyl chloride system. 

Table IV gives the relative product distribution from the vacuum ultraviolet photolysis of ethyl chloride at 40 mm. pressure using the 1236-A. krypton resonance line. Owing to the low intensity of emission from the resonance lamp, higher pressures were not used in the photolysis experiments in order to prevent the major portion of the reaction from occurring in the region of the window where surface interactions are likely. Therefore, to provide a basis for more direct comparison between the photolytic and radiolytic yields, the radiolysis of ethyl chloride was also examined at 40 mm. pressure. The relative yields from several experiments of the latter study are given in Table IV. The lowest conversion yields from the radiolysis at the lower pressure show a relative distribution which is in close agreement with the relative product distribution detected from the radiolysis at 357 mm. Therefore, there is no substantial pressure effect on the decomposition product yields in ethyl chloride over the range 40-357 mm.

Ionic reactions in ethyl chloride have been studied by both mass spectrometric and radiolysis techniques. The radiolysis mechanism advanced on the basis of our experimental observations indicates that the major radiolytic reaction mode in this system is excited neutral molecule decomposition. While the role of ionic reactions in the radiolysis therefore appears to be relatively minor, it was possible to establish a good correlation between the predictions of the mass spectrometric studies with respect to ionic intermediates and the participation of such ions in the radiolytic reaction scheme. These results emphasize the advantages of combining the techniques used here to obtain a complete description of the reactive system. 

Radiation-Chemical Fixation of Molecular Nitrogen and Synthesis of Cyanogen Chloride. The radiation-chemical fixation of molecular nitrogen by hydrocarbons takes place in the liquid phase with relatively high radiation-chemical yields (G. — 1), but it leads to the formation of a broad set of nitrogen containing products, which are difficult to identify (8, 10). The transition to perchlorohydrocarbons considerably restricts the possible products of radiolytic transformations. 

Many research groups have been working on radiation processing of polymer blends, to stabilize the phases and improve performance. The polymers that have been used in the radiolytic studies of blends include polyethylene (PE), polypropylene (PP), ethylene propylene rubber (EPR), polyvinyl chloride (PVC), polystyrene (PS), and polymethylmethacrylate (PMMA). 

Table 11.4. Radiolytic yields (G(/

The dose is often measured by the alcoholic chlorobenzene dosimeter (ISO/ASTM 51538 Ethanol-Chlorobenzene Dosimetry System). This system is based on radiolytic formation of hydrochloric acid in aqueous ethanol solution of chlorobenzene. Usually the solution has the composition 24% monochlorobenzene, 72% ethanol, and 4% water. The chloride ion yield, G(C1 ) = 0.59 pmol is essentially independent of dose up to 100 kGy. 

The aqueous solution of nitro blue tetrazolium chloride was investigated (Kovacs et al. 1999) and it was observed that the NBT " ions were reduced radiolytically first to monoformazan (MF ) and then to diformazan (DF) having high linear molar extinction coefficients at the absorption maxima of 522 nm and 570-610 nm. The formation of formazans was found more pronounced in the presence of alcohol and the aqueous-ethanol nitro blue tetrazolium solutions were found useful for high-dose dosimetry in the dose range of 0.1-30 kGy. 

Examples of grafting from reactions are far more numerous in the recent literature. Poly(vinyl chloride) (PVC) has been used frequently as a macro-initiator for cationic polymerizations. Active centres on the PVC backbone can be generated by radiolytic or chemical methods. Various chemical coinitiators including EtjAlCl, AgPF, and AgSbFe have been employed to induce the cationic polymerization of vinyl and heterocyclic monomers from the backbone. 

Thallium(ii) has been generated in the pulse radiolysis of TF and in IM-HC104. The rates of the reaction of TF + OH and TF + H have been measured, and from data on the Fe TF reaction, the free energy of formation of TF has been shown to be 42 kcal mol. TF plays no part in the TF-TF exchange. Three chloride complexes of TF have also been characterized by radiolytic techniques. Absorption spectra for TICF, TICI2, and TlCls" have been reported. In the complex formation reaction... 

In most natural waters actinides are usually coordinated with hydroxide and carbonate ligands however, waters from ancient salt formations that are proposed as disposal sites for nuclear waste, such as the Waste Isolation Pilot Plant (WIPP) in New Mexico or the Gorleben site in Germany, are saturated with chloride salts. Chloride has been shown to affect the solubility and speciation of actinides significantly compared with their chemistry in inert electrolyte solutions ofsimilar ionic strengths. Radiolytic formation of hypochlorite in chloride brines may resnh in (he... 

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