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Química Nova, Volume: 36, Issue: 4, Published: 2013
  • SBQ apresenta candidatura do Brasil para sediar o Congresso Mundial de Química da IUPAC em 2017 Editorial

    Andricopulo, Adriano D.; Galembeck, Fernando; Ferreira, Vitor F.
  • Synthesis, characterization and study of the properties of a new mononuclear quercetin complex containing Ga(III) ions Artigo

    Simões, Vanessa do Nascimento; Favarin, Lis Regiane Vizolli; Cabeza, Natália Aparecida; Oliveira, Tamires Donizeth de; Fiorucci, Antonio Rogério; Stropa, Jusinei Meireles; Rodrigues, Daniela Cristina Manfroi; Cavalheiro, Alberto Adriano; Anjos, Ademir dos

    Abstract in English:

    Flavonoids are one of the most important compound groups applied as medicine given their antioxidant properties, but several intrinsic properties can be improved through structural modifications to their molecules. Here, the synthesis and characterization of a new gallium (III) complex with quercetin is described. Electrochemical properties, as well as antioxidant and cytotoxic activities, were investigated and compared to the free flavonoid molecule. The mononuclear complex obtained, [Ga(C15H9O7)3].2H2O.2CH3OH.CH3CH2OH, seems more active as a DPPH radical scavenger given its lower oxidation potential compared to quercetin. The new complex cytotoxic responses have shown to be more effective than those of the free flavonoid and of lapachol used as a control.
  • Chemical characterization by GC-MS and phytotoxic potential of non-polar and polar fractions of seeds of Dioteryx odorata (Aubl.) Willd. from Venezuelan regions

    Oliveros-Bastidas, Alberto de J.; Demuner, Antonio J.; Barbosa, Luiz Claudio de Almeida

    Abstract in English:

    Dipteryx odorata (Aubl.) Willd. is a tall arboreal species native to Central and Northern South America. This paper describes the chemical characterization and phytotoxic potential of polar and non-polar extracts from D. odorata seeds. Structural determinations were accomplished by chemical derivatization and analyzed by GC/MS. The chemical composition of the non-polar fraction (hexane and dichloromethane) presented fatty acids as major constituent. Medium polar and polar fractions (ethyl acetate and ethanol: water) contained carboxylic acid and high 6,7-Dyhidroxycoumarin-β-D-glucopyranoside content, not previously reported for seeds of D. odorata. Extracts showed a significant level of phytotoxic activity, correlated to the content of coumarin derivatives, predominantly in the polar fraction.
  • Influence of method of preparation of PtRu/C electrocatalysts on the catalytic activity for the ethanol oxidation reaction in acidic medium Artigo

    Gomes, Walber dos Santos; Silva, Uriel Lean Valente; Souza, José Pio Iúdice de

    Abstract in English:

    In this work the influence of variations in the borohydrate reduction method on the properties of PtRu/C electrocatalysts was investigated. The electrocatalysts were prepared using 1:1 ; 2:1; 5:1; 50:1 and 250:1 molar ratios of NaBH4 to metals. The reduction was also performed by dripping or by fast addition of the solution. The results showed that PtRu nanoparticles obtained by fast addition had the smallest crystallite sizes. It was also noted that the catalytic activity increased as the borohydrate:metal molar ratio increased. The PtRu/C electrocatalyst (50:1) obtained by fast addition presented the best catalytic activity for ethanol electro-oxidation.
  • A Theoretical investigation of a potential high energy density compound 3,6,7,8-tetranitro-3,6,7,8-tetraaza-tricyclo[3.1.1.1(2,4)]octane

    Zhao, Guozheng; Lu, Ming

    Abstract in English:

    The B3LYP/6-31G (d) density functional theory (DFT) method was used to study molecular geometry, electronic structure, infrared spectrum (IR) and thermodynamic properties. Heat of formation (HOF) and calculated density were estimated to evaluate detonation properties using Kamlet-Jacobs equations. Thermal stability of 3,6,7,8-tetranitro-3,6,7,8-tetraaza-tricyclo [3.1.1.1(2,4)]octane (TTTO) was investigated by calculating bond dissociation energy (BDE) at the unrestricted B3LYP/6-31G(d) level. Results showed the N-NO2 bond is a trigger bond during the thermolysis initiation process. The crystal structure obtained by molecular mechanics (MM) methods belongs to P2(1)/C space group, with cell parameters a = 8.239 Å, b = 8.079 Å, c = 16.860 Å, Z = 4 and r = 1.922 g cm-3. Both detonation velocity of 9.79 km s-1 and detonation pressure of 44.22 GPa performed similarly to CL-20. According to the quantitative standards of energetics and stability, TTTO essentially satisfies this requirement as a high energy density compound (HEDC).
  • Pregnanos e outros constituintes das raízes de Macrosiphonia petraea (A. St.-Hil.) Kuntze (Apocynaceae) Artigo

    Assis Junior, Luiz Roberto de; Garcez, Fernanda Rodrigues; Garcez, Walmir Silva; Guterres, Zaira da Rosa

    Abstract in English:

    Macrosiphonia petraea (A. St.-Hil.) Kuntze is a plant popularly known as "velame". Its root infusion is used in the folk medicine of Mato Grosso do Sul, Brazil, for the treatment of inflammatory diseases. Phytochemical investigation of the roots of this species led to the identification of 17 compounds belonging to four different classes: two pregnanes, 12β-hydroxypregna-4,6,16-triene-3,20-dione, neridienone A, and 12β-hydroxypregna-4,6-diene-3,20-dione, cybisterol, one hydroxylated fatty acid, 5-hydroxy-octadeca-6(E)-8(Z)dienoic acid, two lignoids, pinoresinol and 8a-hydroxypinoresinol, ten pentacyclic triterpenoids, and two steroids.
  • Chemical constituents and antioxidant activity of Byrsonima gardneriana (Malpighiaceae) Artigo

    Rolim, Thaísa Leite; Wanderley, Flávia Talita de Sousa; Cunha, Emídio Vasconcelos Leitão da; Tavares, Josean Fechine; Oliveira, Adriana Maria Fernandes de; Assis, Temilce Simões de

    Abstract in English:

    The phytochemical investigation of Byrsonima gardneriana led to the isolation of five triterpenes and one flavonoid: D:B-Friedoolean-5-en-3-one (1), friedoolean-14-en-3-one (2), friedelan-3-one (3), lup-20(29)-en-3-ol (4), 3β-hydroxiolean-12-ene (5) and 3,3',4',5,7-pentahydroxyflavan (6). Their structures were assigned based on spectroscopic analyses, including two-dimensional NMR techniques and comparison with published spectral data. Antioxidant activities of ethanol extract and phases were measured using the 1,2-diphenyl- 2-picryl-hydrazyl (DPPH) free radical scavenging assay, evaluation of total phenolic content and trolox equivalent antioxidant capacity (TEAC).
  • Determination of absolute rate constant for the phenolic hydrogen abstraction reaction by the triplet excited state of xanthone in acetonitrile and in ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate [bmim.PF6] Artigo

    Bertoti, Ada Ruth; Netto-Ferreira, José Carlos

    Abstract in English:

    The triplet excited state of xanthone was generated and characterized by laser flash photolysis in acetonitrile (λmax=620 nm; t=1.8 ms) and in ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate [bmim.PF6] (λmax=620 nm; t=3.0 ms). It reacts with phenols yielding the corresponding xanthone ketyl radical. Stern-Volmer plots for the reaction of triplet xanthone with phenols led to the determination of absolute rate constants for phenolic hydrogen abstraction in the order of ~10(9) Lmol-1s-1 in acetonitrile and ~10(8) Lmol-1s-1 in [bmim.PF6]. The lower diffusioncontrolled rate constant for [bmim.PF6] is responsible for the difference in the phenolic hydrogen abstraction rate constants in this solvent.
  • Trace elements in atmospheric particulate matter from an agro-industrial region in southeastern Brazil Artigo

    Oliveira, Patrícia Lopes de; Figueiredo, Bernardino Ribeiro; Cardoso, Arnaldo Alves; Angélica, Rômulo Simões

    Abstract in English:

    Trace element concentrations were measured in atmospheric particulate matter collected in 2009 and 2010, in a Brazilian region influenced by pre-harvest burning of sugar cane crops. For coarse particles, high concentrations of Al, Fe, K and Ca suggested that re-suspended soil dust was the main source of aerosol trace elements, subsequently confirmed by XRD analysis. High levels of K, Zn, As, Cd and Pb were found in fine particles, confirming the contribution of biomass burning and vehicle emissions, whereas Na, Al, K, Fe and Zn were the representative elements in ultrafine particles, influenced by a diversity of sources.
  • Chemical constituents of Vernonia scorpioides (Lam) Pers. (Asteraceae) Artigo

    Machado, Adalva Lopes; Aragão, Fabiana Martins; Bandeira, Paulo N.; Santos, Hélcio Silva dos; Albuquerque, Maria Rose Jane R.; Pessoa, Otília Deusdênia L.; Silveira, Edilberto R.; Nunes, Edson Paula; Braz-Filho, Raimundo

    Abstract in English:

    The chemical investigation of hexane and ethanol extracts from the aerial parts of Vernonia scorpioides resulted in the isolation and characterization of a new polyacetylene lactone, rel-4-dihydro-4β-hydroxy-5a-octa-2,4,6-triynyl-furan-2-(5H)-one, along with the new ethyl 3,4-dihydroxy-6,8,10-triynyl-dodecanoate, and seven known compounds: taraxasteryl acetate, lupeyl acetate, lupeol, lupenone, β-sitosterol, stigmasterol and luteolin. The structure of all compounds was determined by spectrometric techniques (HR-ESI-MS, ¹H and 13C NMR and IV) and comparison with published spectral data.
  • Trigonelline, 5-caffeoylquinic acid, cafeine and melanoidins levels in commercial Brazilian instant coffees Artigo

    Marcucci, Carolina Tolentino; Benassi, Marta de Toledo; Almeida, Mariana Bortholazzi; Nixdorf, Suzana Lucy

    Abstract in English:

    Commercial Brazilian regular and decaffeinated instant coffees (33 brands) were studied. The levels ranged from 0.47 to 2.15 g 100 g-1 for trigonelline, 0.38 to 2.66 g 100 g-1 for 5-caffeoylquinic acid (5-CQA), 0.24 to 4.08 g 100 g-1 for caffeine, and 0.253 to 0.476 (420 nm) for melanoidins. Variations in bioactive compound levels among batches were observed. There was no relationship between the drying process and the composition of the products. In general, Gourmet and decaffeinated coffees had higher trigonelline and 5-CQA but lower caffeine and melanoidin content than regular products.
  • Anticholinesterase activity and chemical profile of an active chromatographic fraction of ethanolic extract from Bellis perennis L. (Asteraceae) flowers Artigo

    Marques, Thiago Henrique Costa; Santos, Pauline Sousa dos; Freitas, Rivelilson Mendes de; Carvalho, Rusbene Bruno Fonseca de; Melo, Cassio Herbert Santos de; David, Juceni Pereira; David, Jorge Mauricio; Lima, Luciano Silva

    Abstract in English:

    This work describes the isolation of an active flavonoid fraction and identification of isorhamnetin 3-O-β-D-(6''-acetyl)-galactopyranoside from flowers of B. perennis, and also the evaluation of anticholinesterase (AChE) activity of ethanolic extract from flowers (EEF) and the active fraction. The chemical structure of the flavonoid was defined on the basis of spectroscopic ¹H NMR, IR and UV data. EEF or flavonoid reduces AChE activity in vivo, while flavonoid also reduces AChE activity in vitro, showing a value of 1.49 mM for 50% inhibitory concentration (IC50), suggesting potential use as an insecticide or in the treatment of neurodegenerative diseases such as Alzheimer's disease.
  • QSAR modeling: a new open source computational package to generate and validate QSAR models Artigo

    Martins, João Paulo A.; Ferreira, Márcia M. C.

    Abstract in English:

    QSAR modeling is a novel computer program developed to generate and validate QSAR or QSPR (quantitative structure- activity or property relationships) models. With QSAR modeling, users can build partial least squares (PLS) regression models, perform variable selection with the ordered predictors selection (OPS) algorithm, and validate models by using y-randomization and leave-N-out cross validation. An additional new feature is outlier detection carried out by simultaneous comparison of sample leverage with the respective Studentized residuals. The program was developed using Java version 6, and runs on any operating system that supports Java Runtime Environment version 6. The use of the program is illustrated. This program is available for download at lqta.iqm.unicamp.br.
  • Visualization in chemistry education: directions for research and development of educational resources Revisão

    Teruya, Leila Cardoso; Marson, Guilherme Andrade; Ferreira, Celeste Rodrigues; Arroio, Agnaldo

    Abstract in English:

    Visualization is a fast-growing field in science education. This review covers 171 articles published between 2001 and 2010 in 14 science education journals. Major findings include: i - despite the predominance of English speaking countries, interest in the topic has increased in several countries; ii - qualitative research is increasing, but quantitative methodologies prevail; iii - the role of peer interaction in group activities is little investigated; iv - research on the way students and teachers use visualization tools is increasing, but most publications focus on the tools; v - structure of matter remains the most common subject covered.
  • Processing of printed circuit boards of small electrical and electronic devices Nota Técnica

    Henrique Júnior, Sérgio de Souza; Moura, Felipe Pereira de; Correa, Roger de Souza; Afonso, Júlio Carlos; Vianna, Cláudio Augusto; Mantovano, José Luiz

    Abstract in English:

    A hydrometallurgical process applicable to printed circuit boards of small electrical and electronic devices was developed. This involved three leaching steps (60 ºC, 2 h): 6 mol L-1 NaOH, 6 mol L-1 HCl and aqua regia. NaOH removed the resin and flame retardant that covered the circuit boards. HCl dissolved the most electropositive metals and a small amount of copper (~0.3 wt%). Aqua regia dissolved the noble metals. Silver precipitated as AgCl. Gold and platinum were quantitatively extracted with pure methyl-isobutylketone and Alamine 336 (10 % vol. in kerosene), respectively. Slow evaporation of the raffinate crystallized CuCl2.4H2O (89% yield).
  • Optimization and practical implementation of ultrafast 2D NMR experiments

    Queiroz Júnior, Luiz H. K.; Ferreira, Antonio G.; Giraudeau, Patrick

    Abstract in English:

    Ultrafast 2D NMR is a powerful methodology that allows recording of a 2D NMR spectrum in a fraction of second. However, due to the numerous non-conventional parameters involved in this methodology its implementation is no trivial task. Here, an optimized experimental protocol is carefully described to ensure efficient implementation of ultrafast NMR. The ultrafast spectra resulting from this implementation are presented based on the example of two widely used 2D NMR experiments, COSY and HSQC, obtained in 0.2 s and 41 s, respectively.
  • Development and validation of a UV spectrophotometric method to quantify carvedilol Nota Técnica

    Borba, Paola Aline Amarante; Riekes, Manoela Klüppel; Pereira, Rafael Nicolay; Stulzer, Hellen Karine; Vecchia, Debora Dalla

    Abstract in English:

    This paper reports the development and validation of a new analytical method using UV spectrophotometry to quantify carvedilol (CRV) in hydrophilic matrices and raw material. This method was shown to be linear, accurate, precise, robust and to have adequate limits of quantification and detection (LQ and LD, respectively), allowing its use in the dissolution test of hydrophilic matrices. The content of CRV determined through this method was compared with two previously validated methods based on the reference techniques of High Performance Liquid Chromatography (HPLC) and Potentiometric Titrations (PT). ANOVA confirmed the equivalence of these methods, showing no significant differences.
  • ASTM color: a simple and fast method for determining quality of biodiesel produced from used cooking oils Nota Técnica

    Morais, Verônica Santos de; Castro, Eustáquio Vinícius Ribeiro de; Carneiro, Maria Tereza Weitzel Dias; Brandão, Geisamanda Pedrini; Fabri Júnior, Reginaldo; Sena, Denise Rocco de

    Abstract in English:

    In this study, 23 biodiesel samples were produced, 20 from used cooking oil and the remaining 3 from refined soybean oil. The following properties were determined in all of the samples (oil and its respective biodiesel): density; viscosity; total acid number and ASTM color. The results indicated high correlation (R > 0.6) between ASTM color of used cooking oil and total acid number of its resultant biodiesel. This high correlation allows prediction of the quality of the biodiesel produced using a simple and fast procedure such as ASTM color.
  • Theoretical study of electronic transitions using simple and sophisticated methods Educação

    Morgon, Nelson H.

    Abstract in English:

    In this paper, the use of both simple and sophisticated models in the study of electronic transitions was explored for a set of molecular systems: C2H4, C4H4, C4H6, C6H6, C6H8, "C8", C60, and [H2NCHCH(CHCH)kCHNH2]+, where k = 0 to 4. The simple model of the free particle (1D, 2D, and 3D boxes, rings or spherical surfaces), considering the boundary conditions, was found to yield similar results to the sophisticated theoretical methods such as EOM-CCSD/6-311++G** or TD(NStates=5,Root=1)-M06-2X/6-311++G**.
  • Addressing environmental issues: the contribution of teacher-trainers of chemistry teaching curricular components Educação

    Marques, Carlos Alberto; Silva, Rejane Maria Ghisolfi da; Gonçalves, Fábio Peres; Fernandes, Carolina dos Santos; Sangiogo, Fábio André; Regiani, Anelise Maria

    Abstract in English:

    This paper presents the results of a study involving current teachers of the chemistry teaching curricular components of twelve Chemistry licentiate courses at state universities in the South and South-east of Brazil. The aim was to analyse how these curricular components can work together to address environmental issues in Chemistry teacher-training. From analysis of the interviews, it can be ascertained for example that environmental themes in the curricular components analysed are treated with differing levels of intensity and perspectives, and in some cases, have a more illustrative character regarding chemistry concepts.
  • The globally harmonised system of classification, labelling and packaging of chemicals (GHS): an introduction to its application in academic teaching and research laboratories Assuntos Gerais

    Wallau, Wilhelm Martin; Santos Júnior, José Augusto dos

    Abstract in English:

    The present article provides an overview of the Globally Harmonised System of Classification, Labelling and Packaging of Chemicals (GHS) and its implementation in Brazil. Although Classification and Packaging is beyond the scope of the responsibility of academic chemists, labelling of chemicals used in academic laboratories will be required by the competent authorities to ensure the safety of students and staff. Therefore, academic teachers and researchers responsible should be familiarised with the GHS principles outlined here and at least be able to label, by applying these principles, mixtures of substances previously classified by the competent authorities.
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