Síntese de 1-indanonas através da reação de acilação de Friedel-Crafts intramolecular utilizando NbCl5 como ácido de Lewis

The intramolecular Friedel-Crafts acylation reaction of 3-arylpropanoic acids to give 1-indanones can be effected in good yields under mild conditions (room temperature) by using niobium pentachloride. Our results indicate that NbCl5 acts both as reagent (to transform carboxylic acids into acyl chlorides) and as catalyst in the Friedel-Crafts cyclization.

Uma metodologia simples e eficiente para a cloração de compostos aromáticos ativados utilizando o ácido tricloro-isocianúrico

The chlorination of activated aromatic rings is efficiently achieved under mild conditions by reaction of aromatic compounds with trichloroisocyanuric acid in acetonitrile, at room temperature, leading to products in 60-95% isolated yields and good regioselectivity.

Comportamento eletroquímico da N-nitrosotiazolidina ácido carboxílico sobre eletrodos de ouro e mercúrio

The electrochemical behavior of N-nitrosothiazolidine carboxylic acid (NTAC) on gold and hanging mercury electrodes, using the cyclic and square wave voltammetries, was studied. Whereas NTAC suffer reduction in a single step on the mercury electrode, two peaks appears on the cyclic voltammograms on the gold electrode, one anodic peak overlaying the gold oxide process at 1.2 V and one cathodic peak at -0.41 V vs Ag/AgCl, KCl 3.0 mol L-1. The cathodic peak depends on the previous oxidation of NTAC at the electrode surface, presents irreversible and adsorption controlled characteristics and it is suitable for quantitative purposes.

Extração líquido-líquido de ferro(III) e titânio(IV) pelo ácido bis-(2-etil-hexil) fosfórico (D2EHPA) em meio de ácido sulfúrico

This work presents a study on the separation of Fe(III) and Ti(IV) from sulfuric acid leaching solutions of ilmenite (FeTiO3) using liquid-liquid extraction with D2EHPA in n-dodecane as extracting agent. The distribution coefficients (K D) of the elements related to free acidity and concentration of Fe(III) and Ti(IV) were determined. Free acidity was changed from 3x10-2 to 11.88 mol L-1 and D2EHPA concentration was fixed at 1.5 mol L-1. Recovery of final products as well as recycling of wastes generated in the process were also investigated. The LLE process as a feasible alternative to obtain high-purity TiO2.

Uso de scanner em espectrofotometria de absorção molecular: aplicação em experimento didático enfocando a determinação de ácido ascórbico

Quantitative analysis of colored substances is generally performed using a spectrophotometer for detection of radiation. However, the combination of digital images and mathematical conversion of colors is an alternative for quantitative procedures based on colored chemical reactions. This work proposes a didactic experiment using a scanner for determination of ascorbic acid in medicines based on the formation of the Prussian blue complex. Results were in good agreement with a conventional spectrophotometer method and the procedure is attractive for instrumental analysis undergraduate courses.

Síntese, caracterização e análise térmica dos sais de lítio, sódio e potássio do ácido palmítico e do seu éster etílico

Alkaline salts of the palmitic acid were synthesized and characterized from aqueous and ethanolic medium. The salts were characterized by elemental analysis (EA) and infrared spectroscopy (IR). EA and IR, being its synthesis comproved, also characterized the ethyl palmitate. All the salts and the ester were submitted to thermal analysis using thermogravimetry (TG), and differential thermal analysis (DTA) in the temperature ranging from room to 700 ºC under air dynamic atmosphere. Differential scanning calorimetry (DSC) measurements were taken from -90 ºC up to temperatures close to the starting of the decomposition temperature, determined by thermogravimetry, using heating and cooling cycles.

Extração líquido-líquido de urânio(VI) do colofanito de itataia (Santa Quitéria, Ceará) por extratantes orgânicos em presença de ácido fosfórico

This work describes the liquid-liquid extraction of uranium after digestion of colofanite (a fluoroapatite) from Itataia with sulfuric acid. The experiments were run at room temperature in one stage. Among the solutions tested the highest distribution coefficient (D > 60) was found for 40%vol. DEHPA (di(2-ethyl-hexyl)phosphoric acid) + 20% vol. TOPO (trioctylphosphine oxide) in kerosene. Thorium in the raffinate was quantitatively extracted by TOPO (0.1% vol.) in cyclohexane. Uranium stripping and separation from iron was possible using 1.5 mol L-1 ammonium or sodium carbonate (room temperature, one stage). However, pH control is essential for a good separation.

Cloração do anisol, tolueno e nitrobenzeno com ácido tricloroisocianúrico (ATCI): aspectos computacionais sobre a reatividade e regiosseletividade

We present in this educational article a theoretical analysis based on DFT/B3LYP 6-311++G (d,p) and ab initio MP2/6-311++G(d,p) computational calculation about the reactivity and the regioselectivity on the chlorination reaction of anisole, toluene and nitrobenzene, using trichloroisocyanuric acid (TICA) as donor of Cl+. The H.O.M.O. / L.U.M.O. energy and N.B.O. atomic charges of various aromatic systems were calculated in ab initio level. The energies of the reagents and intermediaries were calculated using D.F.T.. These results have been presented as a quantitative example for the S E A mechanism, in the undergraduate organic chemistry disciplines.

Biodegradação de tolueno e óleo de pescado em solos impactados utilizando surfactantes químico e biológico

The process of biodegradation of soils contaminated by animal (raw fish oil) and mineral (toluene) origin compounds was studied, verifying the influence of adding biosurfactants and chemical surfactants and nutrients in the media. The highest removal rate of fish oil was 59.47% obtained in the experiments containing biosurfactant and biostimulate in 90 days process. The highest removal rate of toluene was achieved in 14 days for experiments containing biosurfactant, chemical spreading and biosurfactant with biostimulation, showing great influence of evaporation on the process. The use of surfactants has shown to increase the contaminant bioavailability due to its higher degradation rate.

Biodegradação de fenol por uma nova linhagem de A spergillus sp. isolada de um solo contaminado do sul do Brasil

The main goal of this work was to study the biodegradation of phenol in batch mode by a filamentous fungus isolated from a contaminated site in Southern Brazil. A better performance was obtained by previous adaptation of the microorganism to the toxic chemical. A 2³ experimental design was proposed and it could be observed total phenol degradation in 72 h using 500 mg L-1 glucose, inoculum of 20% and agitation of 200 rpm, resulting a biodegradation rate of 3.76 mg L-1 h-1. In relation to phenol tolerance, Aspergillus sp. LEBM2 was able to consume up to 989 ± 15 mg L-1.

Branqueamento de polpa celulósica kraft de eucalipto com peróxido ácido ativado por molibdênio

Optimum conditions to run the P Mo stage for bleaching eucalyptus kraft pulp were 90 ºC, pH 3.5, 2 h, 0.1 kg/t Mo and 5 kg/t H2O2. The P Mo stage efficiency increased with decreasing pH (1.5-5.5) and increasing temperature (75-90 ºC), time (2-4 h), and hydrogen peroxide (3-10 kg/t) and molybdenum concentration (0.1-0.4 kg/t). The implementation of the P Mo stage, as replacement for the A stage, decreased total active chlorine demand of the OAZDP sequence by 6 kg/t to reach 90% ISO, both in laboratory and mill scale. Such practice resulted in decreased bleaching chemical costs to produce fully bleached pulp of 90% ISO.

Avaliação da biodegradação de matrizes porosas à base de hidroxiapatita para aplicação como fontes radioativas em braquiterapia

Porous ceramic materials based on calcium phosphate compounds (CPC) have been studied aiming at different biomedical applications such as implants, drug delivery systems and radioactive sources for brachytherapy. Two kinds of hydroxyapatite (HAp) powders and their ceramic bodies were characterized by a combination of different techniques (XRF, BET method, SEM, ICP/AES and neutron activation analysis - NAA) to evaluate their physico-chemical and microstructural characteristics in terms of chemical composition, segregated phases, microstructure, porosity, chemical and thermal stability, biodegradation and incorporation of substances in their structures. The results revealed that these systems presented potential for use as porous biodegradable radioactive sources able to be loaded with a wide range of radionuclides for cancer treatment by the brachytherapy technique.

Determinação de ácido valpróico em soro por cromatografia líquida de alta eficiência com detector de arranjo de diodos (CLAE-DAD), após derivatização com brometo de fenacila

Valproic acid (VA) is a drug used to control seizures in several epileptic conditions. In VA pharmacotherapy, therapeutic drug monitoring is recommended to obtain adequate seizure control and avoid toxicity. The aim of this study was to validate a method for the determination of valproic acid in serum, employing high performance liquid chromatography with diode array detection (HPLC-DAD), after derivatization with phenacyl bromide. The calibration curve (y=0.0133x-0.0025) presented good linearity with r²=0.9999. Accuracy (101-115%), intra-assay precision (4.53-8.15%) and inter-assay precision (3.15-6.77%) were acceptable. The quantification limit was 2.0 µg/mL. The method presented similar results to enzyme immunoassay.

Uso das técnicas de infravermelho e de ressonância magnética nuclear na caracterização da reação ácido-base de um cimento odontológico experimental

Glass ionomer cements (GICs) are products of the acid-base setting reaction between an finely fluoro-alumino silicate glass powder and poly(acrylic acid) in aqueous solution. The sol gel method is an adequate route of preparation of the glasses used to obtain the GICs. The objective of this paper was to compare two powders: a commercial and an experimental and to investigate the structural changes during hardening of the cements by FTIR and Al MAS NMR. These analyses showed that the experimental glass powder reacted with organic acid to form the GICs and it is a promising material to manufacture dental cements.

Estudo das interações entre o complexo polieletrolítico trimetilquitosana/carboximetilcelulose e Cu+2, ácido húmico e atrazina em solução aquosa

The polyelectrolyte complex (PEC) resulting from the reaction of sodium carboxymethylcellulose (CMC) and N,N,N-trimethylchitosan hydrochloride (TMQ) was prepared and then characterized by infrared spectroscopy and energy dispersive X rays analysis. The interactions involving the PEC and Cu2+ ions, humic acid and atrazine in aqueous medium were studied. From the adsorption isotherms the maximum amount adsorbed (Xmax) was determined as 61 mg Cu2+/g PEC, 171 mg humic acid/g PEC and 5 mg atrazine/g PEC. The results show that the CMC/TMQ complex has a high affinity for the studied species, indicating its potential application to remove them from aqueous media.