Reactions of pertechnetate ion with thiourea (tu) in a hydrochloric acid solution have been investigated by spectrophotometry. Two consecutive reactions were observed for the formation of a technetium-thiourea complex. The intermediate is considered to be a Tc(V)-tu complex ([TcO(tu)4]3+). The observed reaction rates of these two reactions were found to be second order with respect to the concentration of thiourea. The rate-determining step in the 1st step was concluded tobe the reduction of Tc(VII) to Tc(V) and that in the 2nd step to be the reduction of Tc(V) to Tc(III).
Authors:T. Omori, K. Omori, C. Ochi, K. Yoshihara, and M. Yagi
In order to produce routinely carrier-free96Tc and111In, their simultaneous production was examined by means of the stacked foil method. Both niobium and silver foils were arranged on the target holder so as the desired nuclear reactions took place effectively. Simultaneous irradiation of the target with 35 MeV -particles produced effectively111In and96Tc by the109Ag(, 2n)111In and93Nb(, n)96Tc reactions, respectively. Sufficient amounts of radioactivities for tracer uses are obtained by the irradiation at 5 A current for 2 hrs. In addition, carrier-free96TcO4– in a perchloric acid solution could be prepared by the combined use of precipitation and anion-exchange methods. Separation of carrier-free111In from the silver matrix was done by means of solvent extraction using acetylacetone as a chelating agent.
The chemical species of carrier-free technetium, which were extractable into a TTA-benzene solution on reduction of96TcO
either with NaBH4 or concentrated HCl, were studied by means of silica gel chromatography. Elution peaks ascribed to the formation of Tc/tta/4 and Tc/tta/3 type complexes were observed. The latter complex was also synthesized by recoil effect of Ru/, p/Tc reactions in -irradiated Ru/tta/3.
Radiochemical and spectrophotometric studies on the solvent extraction of tetrachloronitridotechnetate(VI) ion with tetraphenylarsonium chloride into chloroform have been reported. Analysis of the dependence of the distribution ratio for technetium species on the concentration of hydrogen ion (0.1–1.0M) revealed that an equilibrium between tetrachloronitridotechnetate(VI) ion and [(H2OCl3NTc–O–TcNCl3(H2O)]2– is established in the aqueous phase. However, formation of di(-O) dimer was suggested, when the concentration of hydrochloric acid is less than 0.2M. The extraction constant for technetium and formation constant for -oxo technetium nitrido complex were evaluated.
A systematic study of extraction of pertechnetate with tetraphenylarsonium chloride (TPAC) in chloroform from aqueous chloride solutions has been carried out at 25°C at ionic strength of 1.0. Fundamental parameters governing the distribution equilibrium of TPAC were determined. Extraction behavior of pertechnetate was established on the basis of the distribution mechanism of TPAC.
Based on the fundamental parameters governing the distribution equilibrium of tetraphenylarsonium chloride (TPAC) between then-hexane-chloroform and aqueous solutions, the extraction mechanism of pertechnetate with TPAC has been systematically investigated. By the analysis of a relation of the distribution ratio of pertechnetate and the hydrogen ion concentration, the dissociation constant of pertechnetic acid was determined to beKa=2.09±0.18 at 25 °C.
A new chemical species of bis(acetonitrile)bis(acetylacetonato)technetium(III), [Tc(acac)2(CH3CN)2]+, has been prepared by the reaction of tris(acetylacetonato)technetium(III) with acetonitrile in the presence of a strong acid, perchloric or hydrochloric acid. The reaction kinetics were followed by observing spectral change of Tc(acac)3 in the UV-visible region. The complex has been characterized by combination of elemental analyses, IR and UV-visible spectrophotometry, ion-exchange chromatography, and paper electrophoresis. Applicability of this substance to synthesize mixed-ligand technetium(III) complexes was discussed based on the solubility of this complex and the ease of substitution of the acetonitrile ligand.
The distribution behavior of pertechnetate and tetrachloronitridotechnetate(VI) with tetraphenylarsonium chloride (TPAC) was highly affected in the presence of 3,5-dichlorophenol(3,5-DCP). In both cases the distribution ratios of the technetium complexes decrease with an increase in the concentration of 3,5-DCP and no synergistic effect was observed. These features could quantitatively be explained by the formation of an associated complex of TPAC and 3,5-DCP in chloroform solution.
Base hydrolysis of Tc(acac)3 and Ru(acac)3 was studied in 0.1–1M NaOH at different temperatures. In spite of apparent similarity of these complexes Tc(acac)3 showed more complexity than Ru(acac)3 in kinetic behavior. Tc(acac)3 decomposes with a rate, d[Tc(acac)3]/dt=(k1[OH–]+ +k2[OH–]2)[Tc(acac)3], where k1 and k2 at 25°C are (1.67±0.11)×10–5 mol–1·s–1 and (1.71±±0.14)×10–5 mol–2·s–1, respectively. Decomposition of Ru(acac)3 is expressed by the rate equation d[Ru(acac)3]/dt=k[OH–][Ru(acac)3], where k at 37°C is (8.01±0.23)×10–6 mol–1·s–1.