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  • Author or Editor: L. Wojnárovits x
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Abstract  

The -propionic acid methyl ester radical was produced in dissociative electron capture reaction of 2-chloropropionic acid methyl ester. The absorption maxima of the radical are at 310 and 300 nm in cyclohexane and water with extinction coefficients of 440±50 and 400±50 mol–1 dm3 cm–1. The second order decay rate parameter in water is (2.3±0.5)×109 mol–1 dm3 s–1. The peroxy radicals have the characteristics: max=265–270 nm, max=700–900 mol–1 dm3 and 2k=(7±2)·108 mol–1 dm3 s–1.

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Abstract  

In the radiolysis of cyclopentane, cyclohexane and cyclooctane, changing the irradiating particles from γ-rays to heavy ions, there are indications for the increase of the proportion of the H atom forming reaction at the expense of the reactions leading to H2 molecule elimination and to radical production without participation of H atoms. This shift is attributed to changes in charge recombination with the increasing LET from basically geminate recombination to predominantly cross combination. The iodine scavenging results are similar in the three systems which is attributed to the basically diffusion controlled character of the competing reactions.

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Abstract  

Hydrated electrons (e aq ) formed in water radiolysis react with ethyl propionate with a rate parameter of 7.5×107 mol–1 dm3 s–1. The electron adduct in acidic solutions immediately (<100 ns) dissociates, yielding CH3CH2C=0 radical. This process in alkaline solutions is slower, k=1.4×105 s–1. The hydroxyl radicals abstract H atoms in about 50% from the -position of propionate.

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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 reactions of hydroxyl radical and hydrated electron intermediates of water radiolysis were studied in the radiolytic degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) at pH values of 4, 6 and 8. The hydrated electron reactions are also suggested to contribute to the aromatic ring decomposition in addition to the highly effective hydroxyl radical reactions. The experimental results suggest also some contribution from the O2 −•/HO2 pair to the degradation. The degradation efficiency was found to be the highest at pH 8 and the lowest at pH 6.

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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  

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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Abstract  

Formation of oxidizing and reducing radicals has been studied by pulse radiolysis of [Fe(CN)6]4––BrO 3 –CN system in ethylene glycol — water solvent mixture. Oxidizing ·BrO2 and BrO radicals formed by electron scavenging with ·BrO 3 were identified and their reactions were investigated. The reaction of hydroxyl radicals with ethylene glycol leads to formation of reactive radicals with reducing properties and of compounds which reduce slowly in dark the ferricyanide formed in the reaction of ·BrO2 radical with ferrocyanide.

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