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Abstract  

By comparing the composition of products formed during the -radiolysis of structural and geometrical /cis and trans/ isomers of dimethylcyclohexanes, the relationship between molecular structure and ring decomposition reactions was investigated. The yields of products that exist in geometrical isomeric forms /e.g. 2-butenes, 2-octenes/ were considerably different in the irradiation of cis- and transdimethylcyclohexanes: the products reflected the conformation of the decomposed molecule. It was assumed that the ring decomposition is a very fast process taking place within about 1 ps. If biradical intermediates are involved in the reactions, their further transformations occur before attaining conformational equilibrium.

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Abstract  

The C5–C10 cyclolakyl radicals have a weak light absorption in the 240–300 nm wavelength range that is due to Rydberg transition to the 3s orbital. The extinction coefficients at 250 nm are in the range of 350–900 mol–1 dm3 cm–1. At this wavelength for the C6–C10 radicals a local maximum appears. The radical decay obeys second order kinetics. The kinetic characteristics of the cyclic and linear radicals are generally similar, indicating that the rings are flexible and can easily overcome steric constraints in the termination process. Both the light absorption and decay characteristics of the cyclopentyl radical are somewhat different from those of the other radicals that are attributed to the special co-planar arrangement.

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Abstract  

The - and -radiolysis of cyclohexane, cycloheptane and cyclooctane was investigated in the absence and presence of iodine scavenger. Comparison of the distributions of products formed revealed considerable differences between - and -radiolysis, and the decomposition of strainless cyclohexane and strained cycloheptane and cyclooctane.

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Abstract  

The - and -radiolysis of cyclopentane were compared in the presence and absence of iodine scavenger. The G-values of the main hydrocarbon products, cyclopentene and bicyclopentyl are 2.22 and 0.56 molecule/100 eV in -radiolysis and 3.25 and 1.23, respectively, in -radiolysis. During high LET -irradiation the yields of products formed by a radical mechanism are much smaller (G=1.18) than in -radiolysis (G=2.68), whereas unimolecular cyclopentene formation is hardly influenced by LET (G=1.8 and 1.6, respectively).

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Abstract  

Phenoxyl type radicals were produced from tyrosine methyl ester (TME) using azide (N 3 . ) radicals. The rate constant of formation increased from 2·108 dm3·mol–1·s–1 at pH 7 to 4·109 dm3·mol–1·s–1 at pH 11, whereas that of the decay, 2k=(6±1)·108 dm3·mol–1·s–1, remained constant. The maximum yield of the radicals varied with pH and pulse dose consistently with the kinetic scheme, which involved a competition of the oxidation of TME by azide radicals with the natural decay of N 3 . .

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Abstract  

In this paper the computer controlled, automated pulse radiolysis laboratory of the Institute of Isotopes of the Hungarian Academy of Sciences, Budapest, is introduced. The system is equipped with a Linac type accelerator which produces 50 ns–2.6 s pulses of 4 MeV electrons, with an optical detection system and with computerized data acquisition.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
K. Süvegh
,
A. Vértes
,
L. Wojnárovits
,
G. Földiák
,
L. Liszkai
, and
Zs. Kajcsos

Abstract  

Two bisphenol-A type epoxy resins were irradiated by electron beam and studied afterwards by positron lifetime spectroscopy. An interesting result is that despite the considerable amount of free-radicals no inhibition of positronium formation was observed in the two epoxies. Nevertheless several serious differences were detected between the studied polymers. The results suggest that the radiation-resistant properties of epoxies depend strongly on the amount of the curing agent.

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