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[en] The present study shows some polarographic behavior of indium (III) in azide media that is close those observed in a thiocyanate solution. The presence of azide ligand decreases the overpotential in the discharge of indium whose catalytic character can be explained by formation of an azide bridge between electrode and indium (III) increasing the speed of electron transfer. The discharge of indium in azide media is diffusion controlled. As the azide concentration is increased the half wave potential displaces in the cathodic direction. This displacement is due to complex formation. The number of electrons, n, involved in the total process was estimates by the reversible polarographic equation to be 2,7. The potentiostatic coulometry of indium in azide/hydrazoic acid buffer showed a catalytic process where the chemistry regeneration was performed by reaction of hydrazoic acid and indium amalgam. The electrochemistry evidence was the constancy of current as the electrolysis proceeded. The chemistry aspect was the presence of ammonium cation in electrolysed solution. The catalytic process with chemistry regeneration and the formation of a bridge by azide could explain the higher value of current in azide media compared to perchlorate solution. (author)
[pt]O presente trabalho procura mostrar alguns aspectos do comportamento polarografico do indio (III) em meio de azoteto que sao muito semelhantes aos observados em meio de tiocianato. A antecipacao da onda do indio (III) na presenca do anion azoteto constitui carater catalitico cuja explicacao residiria na formacao de ponte de azoteto entre o eletrodo e indio (III) facilitando a transferencia de eletron. O processo que governa a descarga do indio em meio de azoteto e a difusao. O potencial de meia-onda do indio se desloca para regiao catodica com crescentes valores da concentracao de azoteto. Este deslocamento e indicio da formacao de complexos. O numero de eletron total, n, envolvido no processo foi estimado pelo uso da equacao polarografica de onda reversivel, encontrando-se o valor de 2,7. A coulometria potenciostatica mostrou a existencia de processo catalitico na reducao do indio (III) em tampao de azoteto/acido azotidrico, ocorrendo a regeneracao quimica do indio (III) pelo ataque do acido azotidrico ou amalgama formado. A evidencia eletroquimica foi a nao diminuicao da corrente com a eletrolise e o fato quimico foi a constatacao de cation amonio na solucao eletrolisada. A explicacao mais provavel da altura da onda do indio (II) ser maior em meio de azoteto comparativamente ao meio de perclorato de sodio estaria na presenca do fenomeno catalitico de regeneracao quimica e tambem na facilidade de transferencia de eletron atraves da ponte de azoteto. (autor)
[en] The catalytic hydrogenation of organic functional groups such as imine, nitrile, oxime, azide, nitro, and nitroso into the corresponding amines is a fundamental organic transformation. In the course of our study on the synthesis of polyamines, we used the catalytic hydrogenation for the conversion of a simple azide compound into the corresponding primary amine. We found that a significant amount of an unknown product was always accompanied along with the desired amine depending on reaction conditions. The unknown product was identified to be a secondary amine, which was produced through a 'reductive dimerization' process
[en] A stopped-flow method for the determination of 2-mercaptopyrimidine and its 14 derivatives by the iodine-azide has been elaborated. Spectrophotometric detection was applied and the decrease in the absorbance of the iodine-starch complex was monitored at 595 nm within 5 s. The effect of the concentration of the reagents on the rate of the reaction was investigated and a kinetic method for determination of compounds is proposed. 2-Mercaptopyrimidines can be determined at 10-6 to 10-5 mol L-1 level and the relative standard deviation is below 1%. The elaborated method has been applied to the determination of 6-methyl- and 6-propyl-2-thiouracil in drugs
[en] Complete text of publication follows. Ionic liquids may provide a solution to many technological problems. Their properties, negligible vapor pressure, non-flammability and ability to be reused made them attractive alternatives to classical solvents. Our understanding of this new class of solvents is quite poor in some areas. The radiation chemistry of ILs is one of them. Recently absorption spectra of Br2·-, (SCN)2·- and BrSCN·- was observed. The rate constants of several elementary reactions of the intermediate formation in the solution of dibromoethane, SCN- and Br- in methyltributylammonium bis[(trifluoromethyl)sulfonyl] imide R4NNTf2 were studied by ns pulse radiolysis. The rate constants of the reactions between Br2·- and SCN- are of the same order of magnitude as for Br2·- with chloropromazine in R4NNTf2. The energy of Br- solvation is the driving force of Br2·- formation. At this time the formation of Br2·- radical anions with azide anions were studied by pulse radiolysis. Br2·- + N3- → 2 Br- + N3·. We demonstrated that N6·- can be generated in ionic liquids methyltributylammonium bis[(trifluoromethyl)sulfonyl] imide R4NNtf2 according to a reaction. N3· + N3- ↔ N6·- It reveals board absorption band in the range of 650 - 700 nm. Alfassi et al. have shown that N6·- absorb at 650 nm with extinction coefficient of 8000 M-1cm-1.
[en] The present work is a branch of the main work concerned with the complex formation between several metal cations and azide ligand in aqueous media. The polarographic behavior of indium in azide system showed the tendency of complexation. Using polarographic method to determine the half potential of indium at each analytical concentration afforded experimental data to evaluate the constants. The azide concentrations was modified from 1 m to 100 m , the ionic strength held at 2,0 M with sodium perchlorate, indium concentration 7.892 x 10-4 M, and temperature kept constant at 25,00C. (author)
[pt]Apresenta-se uma parte do trabalho principal de formacao de complexo entre varios cations metalicos e do ligante azoteto em meio aquoso. O comportamento polarografico do indio no sistema azoteto mostrou a tendencia de complexacao. Dados experimentais foram fornecidos para avaliacao das constantes, usando o metodo, polarografico para determinar o potencial do indio. As concentracoes de azoteto foram modificadas de mM para 100 mM, a forca ionica manteve-se em 2,0M com NaclO4, a concentracao do indio foi de 7,892 x 10-4 M e a temperatura constante a 25,00C. (C.G.C.)
[en] Complete text of publication follows: Nowadays it is becoming increasingly commonplace for a physician to prescribe an FDG-PET scan, especially in oncology. FDG, short for 2-[18F]fluoro-2-deoxy-D-glucose, is a radioactive derivative of D-glucose that accumulates in tissue according to their degree of D-glucose utilization and is therefore very suitable to detect tumours and evaluate their metabolic state. The radiosynthesis of FDG was achieved for the first time in 1978 but it has been only in the last decade that its routine use in nuclear medicine has really taken on. The reason for this relatively long incubation time is twofold. It takes a certain time for a radiopharmaceutical to prove itself and to convince the medical profession of its utility. In addition there were technical and logistic problems to be solved. How to produce FDG regularly in sufficient quantities at a sufficient number of sites? A key factor in all this is radiochemistry know-how, which has seen considerable progress with time. For example, in the beginning FDG was made in relatively low yield with electrophilic [18F]F2 when today's efficient nucleophilic method with [18F]F- was not available. Indeed, the advent of a reliable method that renders cyclotron-produced aqueous and chemically unreactive [18F]fluoride suitable for nucleophilic substitution reactions has revolutionized radiopharmaceutical development with fluorine-18. It is therefore not a co-incidence that all eleven contributions to the present 'focus on [18F]fluoride radiochemistry', covered by two successive issues of the journal, deal almost exclusively with nucleophilic radio-fluorination. The present first issue (volume 3, number 2) begins with a concise outline of the field by Banister et al., the ideas of which are then developed more in depth in the following contributions. Introduction of fluoride in an aromatic position is less straightforward than aliphatic fluorination, the latter treated by Roeda and Dolle, and its methodology is accordingly more differentiated. This is reviewed in separate contributions by Ermert and Coenen, dealing successively with direct labelling at an activated position and built-up syntheses via small radio-fluorinated synthons. The second issue (volume 3, number 3) will open with the third contribution by Ermert and Coenen, this time on the labelling of electron-rich arenes, completing the initial expose of the state of the art. Then Kuhnast and Dolle will look at the more specific field of macromolecule labelling which is rapidly gaining importance. Especially within this field of macromolecules two developments have recently attracted attention, both directed towards prosthetic group construction. The first is the copper(I)-catalyzed Huisgen coupling between a terminal alkyne and an azide, either labelled with fluorine-18, to give a triazole. This reaction, also known under the name 'click chemistry' will be reviewed by Ross, followed by an article by Mu et al. on radiochemistry based on fluorine-silicon and fluorine-boron bond formation involving structures of the type RSi[18F]F4 -, R'R2Si[18F]F and RB[18F]F3. Then Martarello et al. will describe the recently discovered enzyme that can (radio)fluorinate adenosine giving access to various sugar- and nucleoside-like structures by coupled enzyme reactions. Our compilation will conclude with two contributions on technological developments. Sachinidis et al. give their view on the basic principles of automation, so important for safe and reliable routine production of radiopharmaceuticals while Miller at al take us to the fascinating world of extremely small reaction volumes in micro-fluidic technology that is not unlikely to have a big future in PET chemistry. It is clear that fluorine-18 radiochemistry has reached a certain degree of maturity and continues to strive after perfection and innovation, hopefully leading to new and useful radiopharmaceuticals as successful as FDG.
[en] The direct lactamization of 1,3- and 1,4-azido amides has been achieved using triphenylphosphine and water, affording various γ- and δ-lactams in good to excellent yields. The direct lactamization of the azido amides was performed via the Staudinger-type reductive cyclization in which the amide group acts as the electrophile for lactam synthesis. This lactamization provides a mild, functional group tolerant and efficient route for the synthesis of various γ- and δ-lactams found in natural products and pharmaceuticals. Further studies will be conducted to develop new synthetic routes for the synthesis of various lactams. The lactam ring system is one of the most ubiquitous structural motifs found in natural products and pharmaceuticals. Owing to the prevalence of lactams, their synthesis has attracted considerable attention. Lactams are usually prepared by the coupling of activated carboxylic acid derivatives with amines. Alternative routes include the Beckmann rearrangement of oximes, the Schmidt reaction of cyclic ketones and hydrazoic acid, the Kinugasa reaction of nitrones and terminal acetylenes, the Diels-Alder reaction of cyclopentadiene and chlorosulfonyl isocyanate, transition metal catalyzed lactamization of amino alcohols, and iodolactamization of amides and alkenes. In particular, the intramolecular Staudinger ligation of azides and activated carboxy acids, including esters, is well known as an environmentally friendly and mild protocol for lactam synthesis
[en] The experimental apparatus which was designed to study the wavelength-selected photolysis of gaseous azides has been completely assembled, and much component testing and calibration has been done. Numerous problems with the photolysis laser have precluded full experimental operation. Nevertheless, a few preliminary experiments on the photolysis of HN3 have been done and NH(a 1DELTA) has been positively identified as a major product. The sensitivity of the laser-induced fluorescence detection system has been tested in a few experiments on OH which was produced by chemical methods