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Molecular structure of mono- and 1,2-aminoderivatives of cyclohexane: Steric strain effects as determining factors

Tomé, Luciana I. N.; Rosado, Mário T. S.; Eusébio, M. Ermelinda S.; Redinha, J. S.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
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The conformational study of cyclohexylamine and 1,2-cyclohexylamine derivatives was performed. The potential energy surface of every compound was calculated at B3LYP/6-31G(d) and the conformational energy minima were further optimized at B3LYP/aug-cc-pVDZ level of theory. The geometrical parameters and the electronic energy of each conformer were determined. The internal energy, enthalpy, entropy, Gibbs energy and the relative weight of each conformer in the structure of the respective isomer were calculated at 298.15 K. The steric hindrances in the crowded molecules resulting from the replacement of hydrogens of cyclohexane by amine groups are pointed out by short non-bonded H <--> H distances and by the consequent bond and dihedral angles distortions relatively to the cyclohexane structure.; http://www.sciencedirect.com/science/article/B6TGT-4M40020-2/1/0ae6e9744a075380d2df6ddfef6e7bdf

On the interpretation of the enthalpy of solvation of hydroxyl cyclohexane derivatives in different solvents

Costa, Felisbela S.; Eusébio, M. Ermelinda; Redinha, J. S.; Leitão, M. Luísa P.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
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Scaled particle theory was used for calculating the enthalpy of cavity formation in the solvation process of hydroxyl cyclohexane derivatives in water and in organic solvents. From the values calculated for the enthalpy of formation of the cavity and from those quoted for the enthalpy of solvation, the enthalpy of solute/solvent interaction was determined. This thermodynamic property shows that the formation of a cavity is an important contribution to the enthalpy of solvation, and is strongly dependent on the structure of the solvent. Unexpected results observed for water as compared with organic solvents are due to the differences in the cavity formation term rather than to solute/solvent interactions.; http://www.sciencedirect.com/science/article/B6WHM-45FC659-3P/1/fa45ed4ff2b4aaea60be322822fe1b82

Oxidação aerobica de cicloexano e cicloexeno usando carvão ativado como catalisador; Cyclohexane and cyclohexene aerobic oxidation by using activated carbon as a catalyst

Liliane Schier de Lima
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 24/02/2006 PT
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O interesse nas reações de oxidação do cicloexano e cicloexeno tem sido foco de muitas pesquisas nos últimos anos, objetivando a busca de reações com maiores rendimentos e seletividades. A rota sintética comercialmente utilizada oxida o cicloexano a cicloexanol e cicloexanona com rendimentos muito baixos (em torno de 4 %), fomentando ainda mais a busca por rotas alternativas de oxidação. O presente trabalho estudou a oxidação direta de cicloexano e cicloexeno a 140ºC e pressões de até 50 bar usando carvões ativados de origem mineral e vegetal como catalisadores. O carvão ativado, por se tratar de um material com uma alta área superficial e de característica hidrofóbica, é compatível com reações de hidrocarbonetos e, então, foi utilizado como catalisador para estas oxidações. As oxidações diretas do cicloexano, nas condições em que foram realizadas, apresentaram resultados de conversão abaixo de 1% e, em alguns casos, com resultados irreprodutíveis. Para as reações de oxidação do cicloexeno, além de algumas mudanças nas condições das reações, foram utilizados como catalisadores carvão ativado impregnados com Pd. As reações apresentaram boas conversões, que variaram de 5 a 90%. Os carvões minerais previamente tratados com ácido clorídrico conduziram a melhores resultados nas oxidações catalíticas do cicloexeno...

Copper Containing Silicates as Catalysts for Liquid Phase Cyclohexane Oxidation

Cruz,Rosenira S. da; Silva,Juliana M. de S. e; Arnold,Ulrich; Sercheli,Maurício S.; Schuchardt,Ulf
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2002 EN
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Copper containing silicates have been prepared by an acid-catalyzed sol-gel process. The materials were characterized by X-ray diffraction and fluorescence, EPR spectroscopy, elemental analysis, N2-physisorption, thermogravimetry, differential scanning calorimetry, temperature-programmed reduction, FTIR and UV/VIS spectroscopy. The silicates were shown to be efficient catalysts for the oxidation of cyclohexane with tert-butyl hydroperoxide as oxidant. Cyclohexanol and cyclohexanone were obtained as the main products. The metal was shown to be weakly bound to the silicate matrix and metal leaching was observed. Leaching was quantified by X-ray fluorescence and leaching tests showed that the catalytic activity is due to supported copper species. Leached copper showed no activity in the homogeneous phase.

Thermodynamic study of the solubility of some sulfonamides in cyclohexane

Martínez,Fleming; Ávila,Carolina M.; Gómez,Alfredo
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2003 EN
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The thermodynamic functions Gibbs energy, enthalpy and entropy of solution in cyclohexane, were evaluated from solubility data for a group of sulfonamides over the temperature range from 20.0 to 40.0 °C. The excess Gibbs energy and the activity coefficients of the solutes were also determined. The results are discussed in terms of solute-solvent interactions.

Properties of (μ-Oxo)di-iron complexes and catalytic activity toward cyclohexane oxidation

Parrilha,Gabrieli L.; Ferreira,Sarah S.; Fernandes,Christiane; Silva,Giselle C.; Carvalho,Nakédia M. F.; Antunes,O. A. C.; Drago,Valderes; Bortoluzzi,Adailton J.; Horn Jr.,Adolfo
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2010 EN
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We report herein the synthesis and characterization of two dinuclear μ-oxo iron compounds obtained through the reactions of FeSO4•7H2 O and FeCl3•6H2 O with 1-(bis-pyridin-2-ylmethyl-amino)-3-chloropropan-2-ol (L5), which resulted in the compounds [(SO4)(L5)Fe(μ-O)Fe(L5)(SO4 )]•6H2O, 1, and [Cl(L5)Fe(μ-O)Fe(L5)Cl]Cl2• 2H2O, 2. The electronic spectra of both compounds show absorption bands only in the UV range. The electrochemical analysis showed that the dinuclear unit is more stable under reduction in compound 1 than in compound 2, while the Mössbauer spectroscopy revealed that the monodentate ligands (sulfate and chloride) have a significant influence on the Mössbauer parameters determined for 1 and 2, particularly on the quadrupole splitting values. Both compounds were studied as catalysts in reactions of cyclohexane oxidation, using H2O2 and t-BuOOH as oxidants, in a substrate:oxidant:catalyst ratio of 1000:1000:1. Cyclohexanol, cyclohexanone, cyclohexyl hydroperoxide, t-butyl cyclohexyl peroxide and adipic acid were formed during the process. The experiments revealed that compound 2 is, in general, more active than compound 1 in promoting cyclohexane oxidation.

Metabolism of Benzoate, Cyclohex-1-ene Carboxylate, and Cyclohexane Carboxylate by “Syntrophus aciditrophicus” Strain SB in Syntrophic Association with H2-Using Microorganisms

Elshahed, Mostafa S.; Bhupathiraju, Vishvesh K.; Wofford, Neil Q.; Nanny, Mark A.; McInerney, Michael J.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /04/2001 EN
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The metabolism of benzoate, cyclohex-1-ene carboxylate, and cyclohexane carboxylate by “Syntrophus aciditrophicus” in cocultures with hydrogen-using microorganisms was studied. Cyclohexane carboxylate, cyclohex-1-ene carboxylate, pimelate, and glutarate (or their coenzyme A [CoA] derivatives) transiently accumulated during growth with benzoate. Identification was based on comparison of retention times and mass spectra of trimethylsilyl derivatives to the retention times and mass spectra of authentic chemical standards. 13C nuclear magnetic resonance spectroscopy confirmed that cyclohexane carboxylate and cyclohex-1-ene carboxylate were produced from [ring-13C6]benzoate. None of the metabolites mentioned above was detected in non-substrate-amended or heat-killed controls. Cyclohexane carboxylic acid accumulated to a concentration of 260 μM, accounting for about 18% of the initial benzoate added. This compound was not detected in culture extracts of Rhodopseudomonas palustris grown phototrophically or Thauera aromatica grown under nitrate-reducing conditions. Cocultures of “S. aciditrophicus” and Methanospirillum hungatei readily metabolized cyclohexane carboxylate and cyclohex-1-ene carboxylate at a rate slightly faster than the rate of benzoate metabolism. In addition to cyclohexane carboxylate...

Effects of cyclohexane, an industrial solvent, on the yeast Saccharomyces cerevisiae and on isolated yeast mitochondria.

Uribe, S; Rangel, P; Espínola, G; Aguirre, G
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /07/1990 EN
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Little information on the effects of cyclohexane at the cellular or subcellular level is available. In Saccharomyces cerevisiae, cyclohexane inhibited respiration and diverse energy-dependent processes. In mitochondria isolated from S. cerevisiae, oxygen uptake and ATP synthesis were inhibited, although ATPase activity was not affected. Cyclohexane effects were similar to those reported for beta-pinene and limonene, suggesting that the cyclohexane ring in these monoterpenes may be a determinant for their biological activities.

Metabolism of Cyclohexane Carboxylic Acid by Alcaligenes Strain W1

Taylor, David G.; Trudgill, Peter W.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /05/1978 EN
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Thirty-three microorganisms capable of growth with cyclohexane carboxylate as the sole source of carbon were isolated from mud, water, and soil samples from the Aberystwyth area. Preliminary screening and whole-cell oxidation studies suggested that, with one exception, all of the strains metabolized the growth substrate by beta-oxidation of the coenzyme A ester. This single distinctive strain, able to oxidize rapidly trans-4-hydroxycyclohexane carboxylate, 4-ketocyclohexane carboxylate, p-hydroxybenzoate, and protocatechuate when grown with cyclohexane carboxylate, was classified as a strain of Alcaligenes and given the number W1. Enzymes capable of converting cyclohexane carboxylate to p-hydroxybenzoate were induced by growth with the alicyclic acid and included the first unambiguous specimen of a cyclohexane carboxylate hydroxylase. Because it is a very fragile protein, attempts to stabilize the cyclohexane carboxylate hydroxylase so that a purification procedure could be developed have consistently failed. In limited studies with crude cell extracts, we found that hydroxylation occurred at the 4 position, probably yielding the trans isomer of 4-hydroxycyclohexane carboxylate. Simultaneous measurement of oxygen consumption and reduced nicotinamide adenine dinucleotide oxidation...

Isolation and Characterization of a Cyclohexane-Metabolizing Xanthobacter sp

Trower, Michael K.; Buckland, R. Martin; Higgins, Raymond; Griffin, Martin
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /05/1985 EN
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An unusual Xanthobacter sp., capable of independent growth on cyclohexane as the sole source of carbon and energy, has been isolated from soil by using classical enrichment techniques. The mean generation time for growth on cyclohexane was 6 h. The microorganism showed a limited ability to utilize hydrocarbons, with only alicyclic hydrocarbons closely related to cyclohexane supporting growth. Ultrastructural studies indicated the presence of electron-transparent vesicles in the cyclohexane-grown Xanthobacter sp., but the presence of complex intracytoplasmic membranes could not be identified. A soluble inducible enzyme capable of oxidizing cyclohexane was identified in cell extracts. This enzyme had a pH optimum of 6.5, an absolute specificity for NADPH, and a stoichiometric requirement for molecular O2 which was consistent with the formation of cyclohexanol. The enzyme showed no activity towards straight chain alkanes and only a limited activity towards unsaturated ring compounds. Enzymatic studies with cell extracts have indicated the main route of metabolism of cyclohexane by this Xanthobacter sp. to proceed via cyclohexane → cyclohexanol → cyclohexanone → 1-oxa-2-oxocycloheptane (ε-caprolactone) → 6-hydroxyhexanoate (6-hydroxycaproate) → → adipic acid. Alternative routes involving initial double hydroxylation of the cyclohexane ring may operate fortuituously but are unlikely to represent major pathways for the dissimilation of cyclohexane by this microorganism.

Investigation on neurotoxicity of occupational exposure to cyclohexane: a neurophysiological study.

Yuasa, J; Kishi, R; Eguchi, T; Harabuchi, I; Kawai, T; Ikeda, M; Sugimoto, R; Matsumoto, H; Miyake, H
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /03/1996 EN
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OBJECTIVES: To examine the effect of occupational exposure to cyclohexane on the peripheral nervous system. METHODS: A nerve conduction study was performed on 18 workers exposed to cyclohexane in a luggage factory and on age and sex matched occupationally unexposed controls. 12 workers had been exposed to n-hexane (median 2.8 years) before the start of exposure to cyclohexane. To confirm the effect of exposure, a follow up study was performed on nine workers one year after the first study. The mean exposure to cyclohexane was 1.2 years in the first study. A symptom survey was performed. The exposure was measured by air sampling of the breathing zone of each worker. The urinary metabolite cyclohexanol was also monitored. RESULTS: The concentration of airborne cyclohexane ranged from 5 to 211 ppm. The urinary concentration of cyclohexanol ranged from 0.12 to 1.51 mg/l. There was a strong correlation between the cyclohexane exposure in personal air and urinary cyclohexanol. No differences were found in nerve conduction velocities (NCV) between workers exposed to cyclohexane and age and sex matched controls. The results of the follow up study showed significant improvements in peroneal motor NCV (P < 0.01) and sural sensory NCV (P < 0.05) and in ulnar motor distal latency (MDL...

Quantification of cytochrome P-450-dependent cyclohexane hydroxylase activity in normal and neoplastic reproductive tissues.

Senler, T I; Dean, W L; Murray, L F; Wittliff, J L
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/04/1985 EN
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It is well established that liver microsomal cytochrome P-450 participates in steroid metabolism and probably also in the metabolism of anti-oestrogens such as tamoxifen (Nolvadex). Thus it is possible that variations in cytochrome P-450 levels may influence the responsiveness of human breast and endometrial carcinomas to endocrine therapy. Therefore a simple sensitive spectrophotometric assay for determining levels of cytochrome P-450-dependent cyclohexane hydroxylation activity in breast and uterine microsomes (microsomal fractions) has been developed. Cyclohexane was chosen as a substrate because of the relatively high levels of cyclohexane hydroxylase activity in tumour microsomes and because cyclohexane serves as a substrate for several forms of cytochrome P-450. As previously described [Senler, Dean, Pierce & Wittliff (1985) Anal. Biochem. 144, 152-158], a direct method utilizing isotope-dilution/gas chromatography-mass spectrometry was also developed in order to confirm the results of the spectrophotometric assay. The average activity (cyclohexane-dependent NADPH oxidation) for 139 human breast-tumour microsome preparations was 1.34 nmol/min per mg, which is in the range of that found in untreated mammalian liver (1-3 nmol/min per mg). Also...

Cyclohexane Carboxylate and Benzoate Formation from Crotonate in Syntrophus aciditrophicus▿

Mouttaki, Housna; Nanny, Mark A.; McInerney, Michael J.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
EN
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The anaerobic, syntrophic bacterium Syntrophus aciditrophicus grown in pure culture produced 1.4 ± 0.24 mol of acetate and 0.16 ± 0.02 mol of cyclohexane carboxylate per mole of crotonate metabolized. [U-13C]crotonate was metabolized to [1,2-13C]acetate and [1,2,3,4,5,7-13C]cyclohexane carboxylate. Cultures grown with unlabeled crotonate and [13C]sodium bicarbonate formed [6-13C]cyclohexane carboxylate. Trimethylsilyl (TMS) derivatives of cyclohexane carboxylate, cyclohex-1-ene carboxylate, benzoate, pimelate, glutarate, 3-hydroxybutyrate, and acetoacetate were detected as intermediates by comparison of retention times and mass spectral profiles to authentic standards. With [U-13C]crotonate, the m/z-15 ion of TMS-derivatized glutarate, 3-hydroxybutyrate, and acetoacetate each increased by +4 mass units, and the m/z-15 ion of TMS-derivatized pimelate, cyclohex-1-ene carboxylate, benzoate, and cyclohexane carboxylate each increased by +6 mass units. With [13C]sodium bicarbonate and unlabeled crotonate, the m/z-15 ion of TMS derivatives of glutarate, pimelate, cyclohex-1-ene carboxylate, benzoate, and cyclohexane carboxylate each increased by +1 mass unit, suggesting that carboxylation occurred after the synthesis of a four-carbon intermediate. With [1...

Synthesis and in vitro Antitumor Potency of (Cyclohexane-1,2-Diamine)Platinum(II) Complexes with Aminotris(Methylenephosphonic Acid) as Bone-Seeking Ligand

Galanski, Markus; Slaby, Susanna; Jakupec, Michael A.; Keppler, Bernhard K.
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
Publicado em //2005 EN
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In order to develop platinum complexes with selective activity in primary and secondary bone malignancies and with the aim to optimize antitumor activity, platinum(II) complexes with aminotris(methylenephosphonic acid) as bone-seeking (osteotropic) ligand have been synthesized, characterized and tested in the cisplatin-sensitive ovarian carcinoma cell line CH1. As non-leaving diamine ligands, which are decisive for the cellular processing of DNA adducts, cis-R,S-cyclohexane-1,2-diamine, trans-S,S-cyclohexane-1,2-diamine and trans-R,R-cyclohexane-1,2-diamine have been used, resulting in complexes 1, 2, and 3, respectively. The cytotoxicity of the complexes under investigation decreases in the order 3 > 2 > 1 which is in accord with structure-activity relationships with other (cyclohexane-1,2- diamine)platinum(II) and platinum(IV) complexes: Both trans complexes (2 and 3) display a higher in vitro potency than the corresponding cis isomer (I), with the trans-R,R isomer (3) being the most active in this series. In comparison to the analogous (cyclohexane-1,2-diamine)platinum(II) complexes with bis(phosphonomethyl)aminoacetic acid as osteotropic carrier ligand, the cytotoxicity of 1-3 was found to be 1.5 – 2 fold higher, which is explainable by a different coordination mode of the phosphonic acid ligands (acetato versus phosphonato).

Cyclohexane-1,2-Dione Hydrolase from Denitrifying Azoarcus sp. Strain 22Lin, a Novel Member of the Thiamine Diphosphate Enzyme Family▿†

Steinbach, Alma K.; Fraas, Sonja; Harder, Jens; Tabbert, Anja; Brinkmann, Henner; Meyer, Axel; Ermler, Ulrich; Kroneck, Peter M. H.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /12/2011 EN
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Alicyclic compounds with hydroxyl groups represent common structures in numerous natural compounds, such as terpenes and steroids. Their degradation by microorganisms in the absence of dioxygen may involve a C—C bond ring cleavage to form an aliphatic intermediate that can be further oxidized. The cyclohexane-1,2-dione hydrolase (CDH) (EC 3.7.1.11) from denitrifying Azoarcus sp. strain 22Lin, grown on cyclohexane-1,2-diol as a sole electron donor and carbon source, is the first thiamine diphosphate (ThDP)-dependent enzyme characterized to date that cleaves a cyclic aliphatic compound. The degradation of cyclohexane-1,2-dione (CDO) to 6-oxohexanoate comprises the cleavage of a C—C bond adjacent to a carbonyl group, a typical feature of reactions catalyzed by ThDP-dependent enzymes. In the subsequent NAD+-dependent reaction, 6-oxohexanoate is oxidized to adipate. CDH has been purified to homogeneity by the criteria of gel electrophoresis (a single band at ∼59 kDa; calculated molecular mass, 64.5 kDa); in solution, the enzyme is a homodimer (∼105 kDa; gel filtration). As isolated, CDH contains 0.8 ± 0.05 ThDP, 1.0 ± 0.02 Mg2+, and 1.0 ± 0.015 flavin adenine dinucleotide (FAD) per monomer as a second organic cofactor, the role of which remains unclear. Strong reductants...

Anaerobic degradation of cyclohexane by sulfate-reducing bacteria from hydrocarbon-contaminated marine sediments

Jaekel, Ulrike; Zedelius, Johannes; Wilkes, Heinz; Musat, Florin
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 20/02/2015 EN
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The fate of cyclohexane, often used as a model compound for the biodegradation of cyclic alkanes due to its abundance in crude oils, in anoxic marine sediments has been poorly investigated. In the present study, we obtained an enrichment culture of cyclohexane-degrading sulfate-reducing bacteria from hydrocarbon-contaminated intertidal marine sediments. Microscopic analyses showed an apparent dominance by oval cells of 1.5 × 0.8 μm. Analysis of a 16S rRNA gene library, followed by whole-cell hybridization with group- and sequence-specific oligonucleotide probes showed that these cells belonged to a single phylotype, and were accounting for more than 80% of the total cell number. The dominant phylotype, affiliated with the Desulfosarcina-Desulfococcus cluster of the Deltaproteobacteria, is proposed to be responsible for the degradation of cyclohexane. Quantitative growth experiments showed that cyclohexane degradation was coupled with the stoichiometric reduction of sulfate to sulfide. Substrate response tests corroborated with hybridization with a sequence-specific oligonucleotide probe suggested that the dominant phylotype apparently was able to degrade other cyclic and n-alkanes, including the gaseous alkane n-butane. Based on GC-MS analyses of culture extracts cyclohexylsuccinate was identified as a metabolite...

Caractérisation de la pharmacocinétique suite à l’exposition multivoie au toluène, au n-hexane et au cyclohexane chez le rat

Gagné, Michelle
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
FR
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La contribution de l’inhalation et de la voie percutanée à l’exposition totale à des composés organiques volatils (COV) présents dans l’eau potable est une problématique qui suscite un intérêt grandissant en santé publique et au niveau réglementaire. Jusqu’à tout récemment, seule l’ingestion était considérée dans l’évaluation du risque des contaminants de l’eau. L’objectif de ce projet était de caractériser l’impact de l’exposition multivoie sur la pharmacocinétique et la dose interne de trois COV : le toluène (TOL), le n-hexane (HEX) et le cyclohexane (CYCLO). À cette fin, un modèle expérimental animal a été utilisé et un modèle toxicocinétique à base physiologique (TCBP) a été adapté pour le TOL. Des rats Sprague-Dawley ont été exposés par voies uniques (inhalation, orale et percutanée) ou simultanées (multivoie) aux solvants. Pour le TOL, les trois voies ont été expérimentées, alors que la voie percutanée n’a pas été retenue pour le HEX et le CYCLO. Des prélèvements sanguins ont permis de caractériser les cinétiques sanguines. Les niveaux sanguins, obtenus lors des expositions multivoies, étaient généralement plus élevés que la somme des niveaux associés aux expositions par voies uniques...

Comparação entre os intumescimentos de borracha natural e polibutadieno com alto teor 1,4-cis em solventes (n-octano, ciclo-hexano e esqualeno) e em soluções poliméricas; Comparison between the swellings of natural rubber and polybutadiene with higb CIS-1, 4-content in solvents (n-octane, cyclohexane and squalen) and in polymer solutions; Vergleich zwischen den quellungen von naturkautschuk und polybutãdien mit hohem CIS-1, 4-gehalt in lösungsmitteln (n-octan, cyclohexan und squalen) und in polymerlösungen

Ojeda, Telmo Francisco Manfron
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
POR
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Amostras de borracha natural foram reticuladas por meio de radiação gama (doses de 2, 4, 6 e 8 MRad) e intumescidas: a) em n-octano, ciclo-hexano e esqualeno; b) em polibutadieno líquido (Mn=1830 g/mol; alto teor 1,4- cis) a 45°C; C) em solução de polibutadieno de baixo peso molecular (M,= 1830 g/mol; alto teor 1,4-cis) em n-octano e ciclo-hexano; d) em solução de polibutadieno de alto peso molecular (Mn= 175.000 g/rnol; alto teor 1,4-cis) emn-octano e ciclo-hexano ; e) em solução de borracha natural (Mn=779.000 g/mol) em ciclo- hexano, a 25°C. Amostras de polibutadieno (alto teor 1,4-cis) foram reticuladas por meio de radiação gama (doses de 1,s; 18 e 25 MRad) e intumescidas: a) em n-octano, ciclo-hexano e esquaieno. Salvo quando mencionado em contrário, as amostras de borracha natural e de polibutadieno foram intumescidas nas temperaturas de 25, 35 e 45°C. A partir dos ensaios de intumescirnento acima mencionados, foram determinadas as solubilidades de borracha natural e de polibutadieno em n-octano, ciclo-hexano e esqualeno através dos parâmetros de Flory-Huggins, calculados com o emprego da equação de Flory-Rehner. Verificou-se a influência da temperatura e da concentração de polimero no gel sobre o valor do parâmetro de Flory-Huggins. Também através desse parâmetro procurou-se determinar a compatibilidade entre borracha natural e polibutadieno. Foi demonstrado que cadeias lineares de baixo peso molecular de polibutadieno conseguem penetrar em amostras reticuladas de borracha natural...

Influence of Cyclohexane Vapor on Stick-Slip Friction Between Mica Surfaces

Ohnishi, Satomi; Kaneko, Daisaku; Gong, Jian; Osada, Yoshihito; Stewart, Andrew; Yaminsky, Vassili
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
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Stick-slip friction between mica surfaces under cyclohexane vapor has been investigated with the Surface Force Apparatus. The dynamic shear stress decreased from 60 to 10 MPa with increasing relative vapor pressure (rvp) from 5% to 50%. Between a rvp of 5

Synthesis, characterization of Cosalen/NaY and the catalytic performance for aerobic oxidation of cyclohexane

Yuan,X.; Li,F.; Wang,L.; Luo,H. A.
Fonte: Latin American applied research Publicador: Latin American applied research
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2007 EN
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N,N'-Bis(salicylidene)ethylenediiminocobalt (Cosalen) was encapsulated into the supercage of microporous NaY zeolite via "ship-in-a-bottle" technique. The impregnated Cosalen complex immobilized on the outer surface of the zeolite was also prepared in order to further prove the encapsulation by the flexible ligand method. The samples were characterized by FT-IR, UV-Vis, XRD, TG/DTA and SEM techniques. The oxidation of cyclohexane using oxygen was chosen to evaluate the catalytic performance of encapsulated complex. The encapsulated Cosalen was stable than the neat Cosalen complex and the conversion of cyclohexane reached 24.4% at 130 ºC for 3 h in the CH3CN solution without adding any inducing agents. The higher selectivity for acid including adipic acid indicated that the encapsulated Cosalen exhibited the ability to produce acid from cyclohexane by one-step reaction.