Formation Of Radiolysis Products Research Articles

Experimental studies of some moderately fast processes initiated by radiation

Numerous improvements have been made to the Paterson Institute linear accelerator since its installation in 1967. New light sources, improved light guidance, smaller cells and a wider range of photo-detecting devices are now in routine use. Data are collected and processed by a computer-based method which has replaced the original oscilloscope-based system. Processes taking place over more than a few seconds can be studied with an arrangement combining pulse radiolysis with an ordinary spectrophotometer and arrangements for “single-shot” studies of faster processes are now being designed. Detection methods are also available which do not rely on transmission of light, and transient changes in conductivity can be measured. Among the systems which have been extensively studied are the Fricke dosimeter, in which measured overall yields can now be quantitatively correlated with the rate constants of 34 individual reactions taking place. Studies have also been conducted with peptides and proteins in which electrochemically-driven charge transfers have been demonstrated between methionine, tryptophan, tyrosine and cysteine/cystine units. Free radical reactions in Mitomycin C have been elucidated which are consistent with pulse radiolysis observations and the formation of radiolytic products as determined by HPLC. Adriamycin reduction has also been studied: the Adriamycin semiquinone is unusually stable with respect to dismutation but its lifetime is limited by a decomposition process in which daunosamine is expelled. The expulsion is followed by a further rearrangement. Many of the reactions investigated require tens or hundreds of seconds to reach essential completion.

Radiolysis of 2-propanol in presence of 2-hexanoylfuran

2-hexanoyl-5-(2-hydroxy 2-propyl)furan (HHPF), has been investigated as the principal product of radiolysis of 2-hexanoyl-furan (HF) in 2-propanol. The effect of absorbed dose on the product yields has been examined. Possible mechanisms for the formation of radiolytic products are discussed.

Radiation chemistry of an aqueous solution of glycine: compounds of interest to chemical evolution studies.

We have examined the radiolysis of an O2-free aqueous solution of glycine at absorbed doses of 60Co gamma-radiation of up to 20 Mrad. At least 20 compounds are formed during radiolysis, among them several amino acids, an oligoamine, and the nitrogen-free polymers (Mw less than or equal to 28,000 daltons). When dicyandiamide is present in the solution of glycine, various nitrogen-containing products, including some polymers (Mw less than or equal to 12,000 daltons), are synthesized along with radiolytic products of glycine; polyglycines are not formed. We have determined the radiation-chemical yields of radiolytic-product formation and of decomposition of glycine, and have considered possible free-radical reactions leading to the radiation-induced changes observed.

A quantitative study of the pathways involved in the formation of radiolysis products in ethyl palmitate

AbstractThe various compounds produced by irradiation in ethyl palmitate have been determined by direct mass spectrometry and gas chromatography mass spectrometry. Postulated mechanisms for their formation have been confirmed by a comparison of product yields, and a material balance is shown between the G‐values for products and their putative precursors. The total product yield is seen to be nearly equal to the amount of radiation absorbed. Three new radiolysis products, viz. ethyl α‐ethylpalmitate, ethyl hexadecen‐2‐oate and butyl palmitate are reported.

Effects of various parameters on the formation of radiolysis products in model systems

AbstractEffects of various parameters on the formation of radiolysis products in triplamitin, palmitic acid, oleic acid, caprylic acid and capric acid were investigated. A greater yeild of primary and recombination products was observed in palmitic acid compared to that of oleic acid. In general, higher amounts of recombination products are formed in both acids when irradiated at room temperature than at −45 C. In the short chain acids, the yield of the hydrocarbon recombination product was enhanced in the liquid state. In contrast, the ketone recombination product was formed in greater amounts from solid capric acid than from liquid caprylic acid. In the absence of oxygen, a linear relationship was obtained between the dose and the yield of radiolysis products in tripalmitin. In the presence of oxygen, a considerable increase in the formation of γ‐palmitolactone, n‐3 and n‐2 alkanes was observed at room temperature.

The Radiation Chemistry of Aqueous Solutions of Cyanamide

Oxygen-free aqueous solutions of 0.1 M NH2CN (pH 2.4 and 5) were irradiated with y rays (0.01-25 Mrad). The rate constants determined in competition experiments are: k(H + NH2CN) = 6.7 X 106 M-1 sec-', k(eaq- + NH2CN) = 1.5 X 109 M-1 sec-1, and k(OH + NH2CN) = 8.5 X 106 M -sec-1. Radiation-chemical yields were determined for the decomposition of cyanamide molecules and the formation of several radiolytic products. The following compounds were identified in irradiated solutions: H2, CO2, NH3, urea, biuret, arginine, and a -N=N- molecule assigned to methylaminoazoformamide. Possible reactions of secondary free radicals leading to the formation of radiolytic products were considered by taking into account the model of water radiolysis and the measured radiation yields.

PHOTOLYSIS AND RADIOLYSIS OF THE BENZENE‐FUMARONITRILE SYSTEM

Abstract— The photolytic and radiolytic product formation of the complex benzene‐fumaronitrile are compared. The equilibrium constants for the complexes of benzene‐fumaronitrile and benzene‐maleonitrile determined by UV and NMR spectroscopy are given. The products which were found in both photolysis and radiolysis of the system benzene‐fumaronitrile were biphenyl. phenylsuccinodinitrile and maleonitrile. The production of a 2:1 adduct of fumaronitrile and benzene in very small yields could only be confirmed in the case of photolysis. Additional products in radiolysis were phenylcyclohexadienes and benzonitrile. Experiments using filtered light proved that isomerisation of fumaronitrile to maleonitrile and production of phenylsuccinodinitrile proceed via the excited charge‐transfer complex. There are indications that the excited charge transfer complex is likewise an intermediate in the radiolytic formation of these nitriles. The addition of fumaronitrile to benzene reduces the yield of biphenyl in both photolysis and radiolysis.

Kinetics of defect and radiolytic product formation in single crystal sodium bromate determined from color-center measurements

Kinetics of defect and radiolytic product formation in single crystal sodium bromate determined from color-center measurements

Energy transfer and radiolytic product formation in the system polystyrene–pyrene

AbstractIn γ‐radiolysis of polystyrene at room temperature, the formation of radicals detected by ESR spectroscopy is greatly reduced in the presence of pyrene, while crosslinking and hydrogen production are almost unchanged. The formation of these radicals was shown to start from the first excited singlet state of polystyrene competing with radiationless energy transfer to pyrene. Crosslinking and hydrogen production, on the other hand, are independent of the formation of these radicals and attributable to hot hydrogen or ion‐molecule reactions. Besides energy transfer from polystyrene to pyrene by dipole–dipole interaction the results indicate that intramolecular energy transfer within polystyrene is present.

Radiolysis of gaseous isobutylene by 60Co γ rays. I. Decomposition products

The radiolysis of gaseous isobutylene yields the following products: iso-C4H10, H2, propyne, allene, C3H6, C2H2, C2H4, iso-C5H12, C3H8, C2H6, neo-C5H12, and a polymer. The radiochemical yields decrease with pressure, except for the yield of the polymer. Addition of NO decreases only the yields of iso-C4H10, CH4, C3H8, and C2H6, showing that at least partly these products are formed in radical reactions. A mechanism is proposed accounting for the formation of radiolysis products.