Hidrocarbonetos policíclicos aromáticos (HPAS) em cachaça, rum, uísque e álcool combustível

The concentration of 15 polycyclic aromatic hydrocarbons (PAHs) in 57 samples of distillates (cachaça, rum, whiskey, and alcohol fuel) has been determined by HPLC-Fluorescence detection. The quantitative analytical profile of PAHs treated by Partial Least Square - Discriminant Analysis (PLS-DA) provided a good classification of the studied spirits based on their PAHs content. Additionally, the classification of the sugar cane derivatives according to the harvest practice was obtained treating the analytical data by Linear Discriminant Analysis (LDA), using naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, benz[b]fluoranthene, and benz[g,h,i]perylene, as a chemical descriptors.

Aromaticidade: evolução histórica do conceito e critérios quantitativos

In this paper the evolution of the concept of aromaticity is discussed. It considers not only historical aspects of the aromaticity concept but also the different criteria (theoretical and experimental) that have appeared to explain the properties of the aromatic compounds. The topics range from the isolation of benzene by Faraday (1825) until the modern criteria based on geometries, magnetic properties, resonance energy (RE), aromatic stabilization energy (ASE), topological analyses, and others. A chronological separation of issues concerning aromaticity was made, splitting the definitions before and after the appearance of the quantum chemistry. This work reviews the concept of aromaticity.

Avaliação de solventes de extração por ultrassom usando-se cromatografia líquida de alta eficiência para a determinação de hidrocarbonetos policíclicos aromáticos em solos contaminados

A method using ultrasonication extraction for the determination of 17 polycyclic aromatic hydrocarbons (PAHs), selected by the USEPA and NIOSH as "consent decree" priority pollutants, in soil by High Performance Liquid Chromatography (HPLC) was studied. Separation and detection were completed in 20 min with a C18 columm, acetonitrile-water gradient elution and ultraviolet absorption and fluorescence detections. The detection limits, for a 10 µL of solution injection, were less than 9,917 ng/g in UV detection and less than 1,866 ng/g in fluorescence detection. Several organic solvents were tested for extraction of the 17 PAHs from soils. Acetone was the best solvent among the three solvents tested, and the order of the extraction efficiencies was: acetone>methanol>acetonitrile. Ultrasonication using acetone as solvent extraction was used to evaluate the biodegradation of those compounds in contaminated soil during a vermicomposting process.

Degradação de benzeno, tolueno e xilenos em águas contaminadas por gasolina, utilizando-se processos foto-Fenton

In this work the potentiality of photo-Fenton processes were investigated toward the degradation of aromatic hydrocarbons (BTXs) from water contaminated with gasoline. The main results demonstrated that BTXs can be quickly degraded by photo-Fenton process assisted by solar or artificial UV-A radiation, degradation that leads to generation of characteristic phenolic transient species (ie. phenol, hydroquinone and catechol). In the treatment of contaminated water by photo-Fenton processes assisted by solar light, complete BTXs removal was observed in reaction times of about 5 min. Mineralization of about 90% was also observed by applying a multiple H2O2 addition system.

Estudo da fotocatálise heterogênea sobre Ti/TiO2 na descoloração de corantes sintéticos

The main goal of this paper was to study the degradation of synthetic dyes using photoelectrocatalytic properties of particulate films of TiO2 supported on plates of titanium and stimulated by UV-Vis radiation. The dyes decolorizations were measured using spectrophotometric methods to verify which the conditions on Ti/TiO2 electrode was the best for the photoelectrodegradation of them. The results showed that decolorization rates were higher than 90% during a period of 270 min. FT-IR spectroscopy showed that intermediate substances were formed after the decolorization and N=N group/aromatic structures were preserved independently of the specific structure of the dyes.

O ressurgimento da química de benzino com sililaril triflatos no contexto das reações de inserção em ligações sigma

In this paper we gathered articles concerning insertion reactions of arynes, exclusively generated from 2-(trimethylsilyl)aryl triflates in the presence of fluoride ions, in substrates bearing nucleophilic and electrophilic portions separated by sigma bonds. Accordingly, we stand out the great importance and versatility of such transformations in the preparation of highly functionalized aromatic systems, which are hardly synthesized in just one step for other methods.

Nanocompósitos de poliuretana termoplástica e nanotubos de carbono de paredes múltiplas para dissipação eletrostática

Polyurethane/multi-walled carbon nanotube (MWCNT) nanocomposites have been prepared with nanotube concentrations between 0.01 wt% and 1 wt%. MWCNT as-synthesized samples with ~74 nm diameter and ~7 μm length were introduced by solution processing in the polyurethane matrix. Scanning electron microscopy (SEM) images demonstrated good dispersion and adhesion of the CNTs to the polymeric matrix. The C=O stretching band showed evidence of perturbation of the hydrogen interaction between urethanic moieties in the nanocomposites as compared to pure TPU. Differential scanning calorimetry and positron anihilation lifetime spectroscopy measurements allowed the detection of glass transition displacement with carbon nanotube addition. Furthermore, the electrical conductivity of the nanocomposites was significantly increased with the addition of CNT.

Chemical constituents of Salacia elliptica (Celastraceae)

The chemical investigation of Salacia elliptica allowed to the isolation of 20 constituents: two polyols, one xanthone, a mixture of long chain hydrocarbons, one carboxylic acid, one polymer, two steroidal compounds, one aromatic ester and eleven pentacyclic triterpenes. These triterpenes include 3β-stearyloxy-oleanane, 3β-stearyloxy-ursane, one seco-friedelane, and eight compounds of the friedelane serie. The chemical structure and the relative configuration of a new triterpene 1,3-dioxo-16α-hydroxyfriedelane (15) were established through ¹H and 13C NMR including 2D experiments (HMBC, HMQC, COSY and NOESY) and herein reported for the first time.

Synchronous scanning phosphorimetry for the selective determination of chrysene: a metrological study

Room-temperature phosphorimetry was used to quantify trace levels of chrysene in sugar-cane spirits and in fish bile. A selective phosphorescence enhancer (AgNO3) and synchronous scanning allowed the detection of ng amounts of chrysene. Accuracy (113 ± 17%) and selectivity was evaluated using the CRM-NIST-1647d - Priority Pollutant Polycyclic Aromatic Hydrocarbons in acetonitrile. Analysis of sugar-cane spirit samples enabled recovery of 108 ± 18% which agreed with the one achieved using HPLC. Method's uncertainty was equivalent to 3.4 ng of the analyte, however, the analyte pre-concentration (SPE) improved sensibility and minimized the relative uncertainty. Characterization and homogeneity studies in fish bile were also performed.

Síntese e avaliação da atividade antimicrobiana de furanonas halogenadas e de compostos análogos aos nostoclídeos

Considering the broad spectrum of biological activity of gamma-butyrolactone derivatives, we presented the synthesis of 3,4-dihalo-5-arylidenefuran-2(5H)-ones (17-21) and analogues (24-28) of the natural product nostoclide (7,8). Furanones 17-21 were synthesized from the condensation of aromatic aldehydes with lactones 14 and 15, that were obtained from mucobromic and mucochloric acids. Lactone 15 was converted into the intermediate 23 in 36% overall yield. Compound 23 was then transformed into the nostoclide analogues 24-28. Some of the compounds prepared showed antimicrobial activities against Escherichia coli, Staphylococcus aureus and Bacillus cereus comparable to commercial antibiotics.

Reação da cânfora com boroidreto de sódio: uma estratégia para o estudo da estereoquímica da reação de redução

Reduction of camphor to a mixture of borneol and isoborneol was performed using NaBH4 as the reducing agent under suitable conditions. Although more effective reduction was accomplished using toxic methanol, an alternative non-toxic ethanolic system is described. This experiment is important to introduce undergraduate students in reductive procedures, and can be used to show details on stereoselective procedures on carbonyl moieties (facial diastereoselectivity, Bürgi-Dunitz trajectory, diastereomeric excess).

Síntese de 5-nitro-isatina e 5-cloro-isatina a partir da isonitrosoacetanilida

This article describes the preparation of 5-nitroisatin and of 5-chloroisatin from isonitrosoacetanilide in a single step, using readily available and inexpensive reagents. These reactions require around 90 minutes and may be carried out as an undergraduate experiment, providing an opportunity to discuss the electrophilic aromatic substitution mechanism, as well as spectroscopic techniques for product identification.

Chemical modifications of a natural xanthone and antimicrobial activity against multidrug resistant Staphylococcus aureus and cytotoxicity against human tumor cell lines

A series of 15 ω-aminoalkoxylxanthones containing methyl, ethyl, propyl, tert-butylamino and piperidinyl moieties were synthesized from a natural xanthone isolated from a lichen species. These compounds were tested for their in vitro antibacterial properties against Gram-positive and Gram-negative bacteria and cytotoxicity against a number of human tumor cell lines was too evaluated. The newly synthesized derivatives revealed selective activity against Staphylococcus aureus (Gram-positive), and the most promising results are for a multidrug resistant strain, for which six of these compounds showed good activity (MICs 4 µg/mL). Many derivatives inhibited tumor cells growth and most compounds were active on multiple lines.

Avaliação geoquímica de óleos brasileiros com ênfase nos hidrocarbonetos aromáticos

Aromatic compounds are still poorly evaluated in geochemical studies of Brazilian oil samples. For this reason, the objective of this work was to analyze and evaluate 26 oil samples from four Brazilian sedimentary basins. Aromatic hydrocarbon fractions have been analyzed by gas chromatography coupled to mass spectrometry. The results were also compared with previously evaluated saturated hydrocarbon data. Maturation parameters obtained using the 4- and 1-methyl-dibenzothiophenes and trimethyl-dibenzothiophenes led to the best results because a better grouping was observed. For this correlation, the samples were grouped by maturity degree enabling the routine use of these parameters to evaluate oil maturity levels.

Enantioselective biotransformation of propranolol to the active metabolite 4-hydroxypropranolol by endophytic fungi

The enantioselective biotransformation of propranolol (Prop) by the endophytic fungi Phomopsis sp., Glomerella cingulata, Penicillium crustosum, Chaetomium globosum and Aspergillus fumigatus was investigated by studying the kinetics of the aromatic hydroxylation reaction with the formation of 4-hydroxypropranolol (4-OH-Prop). Both Prop enantiomers were consumed by the fungi in the biotransformation process, but the 4-hydroxylation reaction yielded preferentially (-)-(S)-4-OH-Prop. The quantity of metabolites biosynthesized varied slightly among the evaluated endophytic fungi. These results show that all investigated endophytic fungi could be used as biosynthetic tools in biotransformation processes to obtain the enantiomers of 4-OH-Prop.