Aromaticity
Mostrando 1-12 de 35 artigos, teses e dissertações.
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1. RING CURRENT IN ANTHRACENE AND PHENANTHRENE: CORRECTION TO HÜCKEL PARAMETERS
Excessive degeneracy in the ground state of the π-electron energy levels of anthracene was removed using the Hückel method by correcting the Coulomb integral of the four central carbon atoms. A further correction to the resonance integral was proposed based on the ring-current model, which describes the π-ring current flow along the molecule’s perimeter
Química Nova. Publicado em: 2022
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2. Structural Characteristics of Lignite Char from Different Pyrolysis Reactors and the Influence on Their Gasification Reactivity
The gasification reactivity of coal char is affected by numerous experimental variables, and char structure is one of the dominant factors. In this work, Raman spectroscopy, powder X-ray diffraction (XRD), and N2 adsorption were used to investigate the physical and chemical structure of char prepared under different pyrolysis conditions. Three kinds of pyrol
Journal of the Brazilian Chemical Society. Publicado em: 2022
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3. Humic Substances and Chemical Properties of an Acrisol Amended with Vermicomposted Vegetal and Animal Residues
ABSTRACT Vermicomposted vegetal and animal residues are rich in nutrients and humic substances and thus can be applied to the soil as a source of functionalized organic matter (OM) and as an alternative to chemical fertilizers. In Southern Brazil, many animal and vegetal residues are easily accessible. Therefore, this study aimed to evaluate alterations in s
Rev. Bras. Ciênc. Solo. Publicado em: 16/05/2019
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4. Carbon in Physical Fractions and Organic Matter Chemical Composition of an Acrisol after Amazon Forest Burning and Conversion into Pasture
The aim of this study was to investigate impacts of Amazon Forest (AF) fire and conversion to pasture on carbon accumulation in particle size fractions and organic matter (OM) composition of an Acrisol. Soil samples were collected (0.00-2.00 m depth) in three sites: native AF (NAF); AF under natural regeneration for two years after burning (BAF); 23-years ol
J. Braz. Chem. Soc.. Publicado em: 2019-02
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5. TOPOLOGIA DOS ORBITAIS MOLECULARES DE POLIENOS PARA DEDUZIR ENERGIAS RELATIVAS E AVALIAR AROMATICIDADE
A didactic alternative approach is proposed for deducing the molecular orbital topology of acyclic and cyclic polyenes and then evaluating their bonding, antibonding, and nonbonding character. The relative energies of molecular orbitals of neutral molecules and ions were described, in addition to the orbital degeneracy to cyclic conjugated polyenes, and the
Quím. Nova. Publicado em: 2018-07
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6. 1,2,4- and 1,3,4-Oxadiazoles as Scaffolds in the Development of Antiparasitic Agents
In this review, we present the potential use of the heterocyclic oxadiazole rings in the design and synthesis of new drugs to treat parasitic infections. We intend to compare herein all the four isomeric forms of oxadiazole rings as well as discuss the differences and similarities between them. In addition, we discuss aspects on their reactivity that justify
J. Braz. Chem. Soc.. Publicado em: 2018-03
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7. Impact of HNO3 Solution Treatment of South Brazil Coal Matrices on Their Chemical Composition and Humic Acids Yield
In this study, changes on the chemical composition and on the humic acids yield of coal matrices promoted by 25% HNO3 treatment were investigated, by means of elemental, thermogravimetric analyses, and Fourier transform infrared spectroscopy (FTIR). The "run of mine" (ROM) matrix C-MTR (ROM coal) showed the highest C content (41%), highest C/N ratio (76) and
J. Braz. Chem. Soc.. Publicado em: 2017-05
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8. COMPARISON BETWEEN ASPHALTENES (SUB)FRACTIONS EXTRACTED FROM TWO DIFFERENT ASPHALTIC RESIDUES: CHEMICAL CHARACTERIZATION AND PHASE BEHAVIOR
Asphaltenes are blamed for various problems in the petroleum industry, especially formation of solid deposits and stabilization of water-in-oil emulsions. Many studies have been conducted to characterize chemical structures of asphaltenes and assess their phase behavior in crude oil or in model-systems of asphaltenes extracted from oil or asphaltic residues
Quím. Nova. Publicado em: 2016-01
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9. Processo de estabilização de resíduos orgânicos: vermicompostagem versus compostagem
Two processes are used to stabilize organic wastes: composting and vermicomposting.There are no studies in the literature showing which process is most effective over the short term. In this study, 3 organic wastes were composted and vermicomposted for 90 days, and the parameters pH, effective cation exchange capacity, total organic carbon, total Kjeldahl ni
Quím. Nova. Publicado em: 2013
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10. Frações da matéria orgânica e propriedades redox de substâncias húmicas em sedimentos de oceanos profundos
Previous studies have verified that free radicals such as quinone moieties in organic matter participate in the redox reactions in natural systems. These functional groups were positively correlated with the increase in aromaticity and hydrophobicity of the humic substances. As an alternative to relatively complex and expensive spectroscopic methods, the red
Quím. Nova. Publicado em: 2013
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11. Separation and characterization of asphaltenic subfractions
The structure of the various asphaltenic subfractions found in crude oil was evaluated. For this purpose, C5 asphaltenes were extracted from an asphaltic residue using n-pentane as the flocculant solvent. The different subfractions were isolated from the C5 asphaltenes by the difference in solubility in different solvents. These were characterized by infrare
Quím. Nova. Publicado em: 2012
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12. Avaliação de tecnologia para redução da viscosidade de resíduos pesados de petróleo utilizando laser / Assessing technology for reducing the viscosity of heavy petroleum residues using laser
The use of infrared radiation produced by a CO2 laser in visbreaking of heavy fractions of petroleum was assessed. The main criterion used to evaluate the technology was to compare the viscosities of atmospheric distillation residues before and after being irradiated under different operating conditions of the laser. A suitable profile for comparison was dev
Publicado em: 2011