Papers by Jan Willem J van Dorp
Appl. Radiat. Isot., 2018
The neutron irradiation of molybdenum hexacarbonyl has been systematically studied to identify po... more The neutron irradiation of molybdenum hexacarbonyl has been systematically studied to identify possible improvements for the production of molybdenum-99. After irradiation, the targets were dissolved in dichloromethane, and Szilard-Chalmers liquid-liquid extraction was carried out with aqueous extractants.
The effects of the irradiation time, the aqueous phase composition and the irradiated mass were studied with a focus on the chemistry involved. Stable extraction yields of 20 % were obtained with enrichment decreasing with target decomposition. Improved enrichment requires decreased decomposition.
• 99Mo yield depends on recombination processes and the extractant.
• 98Mo mass transfer depends on target decomposition, concentration and the extractant.
• Enrichment depends mainly on the target decomposition.
The Journal of Organic Chemistry, 2008
The photochemical reactions of a series of triaryl vinyl halides 1X in acetic acid and in acetoni... more The photochemical reactions of a series of triaryl vinyl halides 1X in acetic acid and in acetonitrile have been studied using product analysis as a function of the time of irradiation. The quantum efficiencies of formation of the products derived from the photogenerated vinyl cations 1+ depend on the α-aryl substituent, the β-aryl substituent, the leaving group X (= bromide or chloride), and the temperature at which the irradiations are carried out. Hammett correlation or noncorrelation of the α-aryl substituent effects with (excited-state) substituent constants indicates that the ions 1+ are formed directly from the excited states of 1X by heterolytic cleavage of the carbon−halogen bond. Homolytic cleavage, yielding radicals 1•, is a parallel process: the partitioning into ion and radical occurs in the excited state. This conclusion is corroborated by the leaving group effect and the temperature effect. By performing the photochemical reactions of 1X in the presence of HOAc and/or NaOAc as well as the labeled common halide ion 82Br− or 36Cl−, the relative reactivities of the cations 1+ toward these nucleophiles were determined. The selectivities follow the Reactivity−Selectivity Principle. The temperature effect data show that the reactions of the cations with the anionic nucleophiles are (de)solvation controlled and their reactions with the neutral nucleophile activation controlled.
Int. J. Radiat. Appl. Instrum. A: Appl. Radiat. Isot., 1991
Possibilities and limitations of the perturbed angular correlation technique were investigated in... more Possibilities and limitations of the perturbed angular correlation technique were investigated in a study of water-pools of reversed micelles of sodium-diethylhexylsulphosuccinate in iso-octane. Probe nuclide for the measurements was reactor produced 111mCd in the form of Cd2+-ions. The results indicate that Cd2+-ions are present inside the water-pool and predominantly experience the movements of the surrounding H2O molecules. An increase in the average number of Cd2+-ions per micelle seemed to have consequences for the size of the pools and, consequently, of the reversed micelles.
Journal of Organic Chemistry - J ORG CHEM, 1989
The exchange (ex) and the accompanying isomerization (isom) in the reaction of methyl (E)- and (Z... more The exchange (ex) and the accompanying isomerization (isom) in the reaction of methyl (E)- and (Z)-β-chloro-α-cyano-p-nitrocinnamates [(E)-5 and (Z)-5] with 36Cl‾ in acetonitrile were investigated. Exchange was much faster than isomerization, kex/kisom = 54 [(E)-5] and 123 [(Z)-5]. Both exchange and isomerization were faster for (Z)-5 than for (E)-5. The exchange was a relatively fast process, and extrapolation suggested that kex(Cl‾)/ksubstitution(piperidine) of 5 is 2.7. The results are discussed in terms of formation of intermediate carbanion, which exchanged the chloride with highly preferred retention. The modes of rotations leading to inversion (isomerization) were analyzed, and it was shown that isomerizations via 120° counterclockwise rotation and 180º clockwise rotation around the Cα-Cβ bond in the carbanion are distinguishable in principle, although we failed to determine the mode of rotation in our system. The relatively high nucleophilicity of Cl‾ was ascribed to lower hidden reversal of the nucleophilic attack by Cl‾ than in less activated systems. The differences in reactivity
of (Z)-5 and (E)-5 were analyzed in terms of steric interactions in the transition states for the 60° and 120° internal rotations.
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Papers by Jan Willem J van Dorp
The effects of the irradiation time, the aqueous phase composition and the irradiated mass were studied with a focus on the chemistry involved. Stable extraction yields of 20 % were obtained with enrichment decreasing with target decomposition. Improved enrichment requires decreased decomposition.
• 99Mo yield depends on recombination processes and the extractant.
• 98Mo mass transfer depends on target decomposition, concentration and the extractant.
• Enrichment depends mainly on the target decomposition.
of (Z)-5 and (E)-5 were analyzed in terms of steric interactions in the transition states for the 60° and 120° internal rotations.
The effects of the irradiation time, the aqueous phase composition and the irradiated mass were studied with a focus on the chemistry involved. Stable extraction yields of 20 % were obtained with enrichment decreasing with target decomposition. Improved enrichment requires decreased decomposition.
• 99Mo yield depends on recombination processes and the extractant.
• 98Mo mass transfer depends on target decomposition, concentration and the extractant.
• Enrichment depends mainly on the target decomposition.
of (Z)-5 and (E)-5 were analyzed in terms of steric interactions in the transition states for the 60° and 120° internal rotations.