Radiolysis in the solid state

3-Deoxyglucosone / 3-Deoxygluconic acid / 3-Deoxy-4-keto-glucose 0.2 

3-Deoxy-4-keto-glucose / 2-Deoxy-3-keto-glucose 0.19 

It can be seen that in contrast to its radiolysis in aqueous solution (see Table 1), in the solid state there is a larger contribution from fragmentation products which we attribute to the participation of oxyl radicals under these conditions. As expected, hydrogen is a major product and the material balance is poor despite the fact that a large number of products have been quantified (Table 3). Again, the missing complement should mainly consist of dimers which would escape analysis. 

Y Radiolysis of crystalline D-fructose. Products and their G values. Further (as yet not quantified) products are glyceraldehyde, 3-butanone-l,2-diol, 2- and 3- 

Radiation-induced chain reactions in some crystalline carbohydrates. The chain 

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Figure 1. ESR spectra of isobutyric acid following gamma radiolysis in the solid state at (A) 77 K (B) 195 K.

Cherville (Ref 45) exposed both solid and dissolved RDX to 7-radiolysis. Radiolysis in the solid state showed a delayed decompn, resulting from the diffusion of N02 created and trapped during the irradiation. He concludes that RDX is a radiation-resistant expl... 

The nature of the first type of thermal reactions is as yet only speculative. The two obvious possibilities seem to be (1) reaction of an incomplete molecule (radical) with an unbound nearby ligand, made available by recoil fragmentation, radiolysis, chemical dissociation, or the presence of an external atmosphere and (2) reaction of the moiety with a nearby molecule to abstract a ligand. The first type with an external source of CO has been clearly demonstrated for the case of the Group VI carbonyls which, when heated in an atmosphere of CO (up to 100 atm pressure) showed a marked increase in yield. A much smaller enhancement of yield in vacuo was attributed (99) to radiolytic dissociation, because of the influence of irradiation at various y-fluxes. The alternative possibility—that of equilibrium dissociation of Cr(CO)6 in the solid state—has not been investigated. 

This sequence of formation of radical cation which is followed by a C—S bond scission into alkyl radical and alkyl sulfonyl cation was previously suggested by the same authors for the radiolysis of poly(olefin sulfone)s in the solid state and was confirmed by scavenger studies . Seavengers are ineffeetive in erystalline solids such as dialkyl sulfones and hence eould not be used in this study. 

Again the close correspondence between the measured radical and carbon dioxide yields for 7-radiolysis of the N-acetyl amino acids in the solid state suggests that the mechanisms for radical production and carbon dioxide formation are closely related, as they were for the aliphatic carboxylic acids. The following mechanism has been proposed (5.) in order to account for the major degradation products and observed radical intermediates. 

POLYCARBOXYLIC ACIDS The gamma radiolysis of the homopolymers of acrylic, methacrylic and itaconic acids have been investigated in the solid state at 303 K, and in each case the yields of carbon monoxide, carbon dioxide and of radical intermediates have been measured. These are reported in Tables VII and VIII respectively. 

POLYAMINO ACIDS Aliphatic polyamino acids irradiated in the solid state have been reported to undergo N-Ctf, main-chain, bond scission on gamma radiolysis (9) and the stable radical intermediates formed following radiolysis at 303 K are alpha carbon radicals, as observed in the N-acetyl amino acids. 

Racemizations in the crystalline state have a long history. It is known that L-a-amino acids slowly racemize in the solid state [62]. As this also happens in solid proteins the implications are manifold, not only in pure chemistry but also in biochemistry, nutrition, food technology, and geology. Therefore, techniques have been developed to determine the dl ratio of amino acids down to 0.1% and inversion rate constants have been determined under acid hydrolysis conditions [63]. One could think of very slow deamination and readdition of the amine or an enolization mechanism. However, such reactions can also be induced by photolysis or radiolysis from natural sources [64]. 

Pulse radiolysis is a very powerful technique which can be employed to form solutions of nickel(III) and nickel(IV) complexes. The complexes cannot generally be isolated in the solid state, but their properties can be directly investigated by several physicochemical techniques. 

Radiation techniques are powerful tools1- for the study of free-radical reactions both in solution and in the solid state. In aqueous solution, the y-radiolysis of the solvent water gives rise to OH radicals, sol-... 

Despite the present poor understanding of the primary processes, the radiolysis of carbohydrates is a unique way to generate carbohydrate radicals within the carbohydrate matrix. It has enabled some interesting chain reactions to be detected (see Sect. IV,1). Many radical reactions observed in aqueous solution are also observed in the solid state. In addition, there are reactions that are more pronounced in the solid state, and their products can be studied more readily than in the liquid state. 

Schuchmann MN, von Sonntag C (1988) The rapid hydration of the acetyl radical. A pulse radiolysis study of acetaldehyde in aqueous solution. J Am Chem Soc 110 5698-5701 Schuchmann MN, von Sonntag C, Tsay YH, Kruger C (1981) Crystal structure and the radiation-induced free radical chain- reaction of 2-deoxy-p-D-erythro-pentopyranose in the solid state. Z Naturforsch 36b 726-731... 

Spectra of the CH3CHOH radical have been obtained from the radiolysis of pure and aqueous ethanol77. These are shown in Fig. 11. The assignment is based on a combination of esr studies in the solid state, the effects of isotopic substitution, and product analysis. In aqueous solution the radical arises via the reactions... 

The luminescence properties of the decatungstolanthanate anions, especially [Eu(W5Oi8)2]9 , have attracted considerable attention, both in the solid state and solution (Blasse et al., 1981a, 1981b Blasse and Zonnevijlle, 1982 Ballardini et al., 1983 Darwent et al., 1986 Blasse, 1988 Sugeta and Yamase, 1993 Ozeki and Ya-mase, 1993c Lis et al., 2003). Electroluminescence cells based on alkaline earth metal salts of the europium anion have been described (Yamase and Ueda, 1993) and the results of pulse- and continuous-radiolysis of solutions of the europium and neodymium anions have been reported (Mulazzani et al., 1985). 

Radiation has been shown to be a feasible way to convert higher DP alginates to lower DP alginates with improved properties (King, 1994). Loss of t accompanying such depolymerizations can transform pseudoplastic fluids to Newtonian fluids. In carrageenans, radiolysis was shown to be initially rapid and then to decrease to a constant, low, radiation-insensitive DP the rate was faster in solution than in the solid state (Marrs, 1988). 

Kozlov [45] studied the effect of temperature from —196 to 50 °C on the decay of radicals formed during radiolysis of EPR in the solid state by ESR spectroscopy. The radical decay process at low temperature begins before movement of the macromolecules relative to one another and is dependent on the migration mechanism with a very low energy of activation. This process consists of migration of the secondary ions, formed by the capture of charges by free-radicals. That the radical decay process involves a combination of reactions between the radicals... 

Terryn H, Deridder V, Sicard-RoseUi C, Tilquin B, Houee-Levin C. (2005) Radiolysis of proteins in the solid state An approach by EPR and product analysis. J Synchrotron Rad 12 292-298. 

The irradiation of substances that form crystals containing discrete molecules held together by dispersion forces results in radiolysis in the conventional sense. For example, the radiolysis of aliphatic carboxylic acids in the solid state yields hydrogen, carbon monoxide. 

The effect of y- irradiation on sulfacetamide sodium in aqueous solutions and in the solid state has been studied. Pulse radiolysis and steady state experiments demonstrate that hydrated electrons (Saq) and hydroxyl radicals (OH.) are mainly responsible for the degradation between 1CT4 and 1.2 M solute concentrations. The reaction with eaq yields sulfanilic acid and an unidentified product (124). 

The exact nature of the initiating species is not known in most cases. In principle they could be positive or negative ion radicals as shown. It seems more likely however that normal carboniuiT ions or carbanions are formed and that these are the true initiators. This is implied, however, by gas phase or solid state studies. Pulse radiolysis in the liquid state is now beginning to give more direct evidence of the exact nature of the processes. 

A major chemical effect of y-rays on simple peptides such as the N-acylamino acids under oxygen-free conditions, both in the solid state and in concentrated aqueous solution, leads to formation of labile amidelike compounds which are readily degraded on mild hydrolysis to yield ammonia as a characteristic product. Several classes of nitrogen-deficient products are formed concomitantly with the ammonia. Earlier communications have discussed certain limited aspects of the radiolytic lability of simple peptides in the solid state and in concentrated solutions (9, 10, 18). The radiation chemistry of these systems is more complex than that involved in the radiolysis of simple peptides in dilute oxygen-free aqueous solution under which conditions main-chain degradation is of minor importance (10). In this paper we report detailed experimental evidence... 

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