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Catalytic wet air oxidation of low molecular weight carboxylic acids using a carbon supported platinum catalyst

Gomes, Helder; Figueiredo, José; Faria, Joaquim
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
689.96625%
Aqueous solutions of low molecular weight carboxylic acids, such as acetic, propionic and butyric acids, were treated by catalytic wet air oxidation (CWAO) using a carbon supported platinum catalyst. Oxidation in the presence of the catalyst, in a stirred reactor, was carried out at 200 C and 6.9 bar of oxygen partial pressure, with conversions (after 2 h) ranging from 59.4 to 75%, and selectivities to gaseous products of up to 100%. Initial rates for conversion varied from 184 (butyric acid) to 260 mmol h−1 g−1 Pt (propionic acid). The activation energy for butyric acid conversion was found to be 56.7 kJ mol−1.

Modeling of association effects in mixtures of carboxylic acids with associating and non-associating components

Ferreira, Olga; Fornari, Tiziana; Brignole, Esteban A.; Bottini, Susana B.
Fonte: Universidad Nacional del Sur Publicador: Universidad Nacional del Sur
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
687.3718%
http://apps.isiknowledge.com/full_record.do?product=UA&search_mode=GeneralSearch&qid=6&SID=V21Di6PajaHLPoM3@AJ&page=1&doc=1&colname=WOS; The group contribution with association equation of state GCA-EOS has been applied to calculate thermodynamic properties of pure compounds and mixtures of carboxylic acids with paraffins, alcohols, water and gases, at low and high pressures. Two associating groups, OH and COOH, were defined. Self- and cross-association in these mixtures were quantified through two parallel COOH/COOH and OH/OH associations. The validity of this approach is supported by an excellent representation of pure compound properties (vapor pressures and compressibility factors) and phase equilibria in mixtures of (associating + inert) and (associating + associating) components at low and high pressures.

Photochemical reactivity of matrix-isolated monomeric carboxylic acids

Fausto, R.; Maçôas, E. M. S.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
Relevância na Pesquisa
587.28234%
When used together with conventional spectroscopic methods (e.g. infrared spectroscopy), matrix isolation constitutes a very convenient technique to undertake photochemical studies on single molecules that are not easily accessible to experiment under other sampling conditions, such as carboxylic acid monomers, which show a strong tendency to aggregate. Once a matrix of a given substance has been prepared, in situ irradiation of the target matrix-isolated molecule at a proper wavelength enables the promotion of different types of photochemical processes which, most of times, can also be easily probed spectroscopically. These include conformational interconversions, tautomerization reactions and fragmentation processes (including photodegradation reactions). In this paper, results of both electronic and vibrational photochemical studies carried out on a series of different matrix-isolated carboxylic acid monomers are presented. Besides more conventional techniques, an approach based on irradiation at a frequency matching that of the first overtone of a particular vibrational mode is described.; http://www.sciencedirect.com/science/article/B6TGS-435M5SD-5/1/81330f5693ded5ed02059babc57fe626

Structure elucidation and photochemistry of substituted carboxylic compounds by low temperature matrix-isolation and solid state vibrational spectroscopy

Fausto, Rui; Maçôas, Ermelinda M. S.; Kulbida, A.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
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583.15586%
Molecular structures and chemical reactivity (aggregation, phase transitions and photochemistry) of a series of substituted carboxylic acids were studied by low temperature matrix isolation and solid state vibrational spectroscopy, complemented by ab initio molecular orbital calculations. The conformational preferences exhibited by the isolated molecules of the systems under study are analyzed, and the effects of aggregation, temperature change and irradiation are discussed.; http://www.sciencedirect.com/science/article/B6TGS-3XWJTTR-9/1/466ca6f7ee433ca22e92e67cb3ce3753

Induction of the Mitochondrial Permeability Transition in Vitro by Short-Chain Carboxylic Acids

Palmeira, C. M.; Rana, M. I.; Frederick, C. B.; Wallace, K. B.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
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704.24836%
We recently reported that acrylic acid (AA) induces the MPT in vitro, which we suggested might be a critical event in the acute inflammatory and hyperplastic response of the olfactory epithelium. The purpose of the present investigation was to determine if induction of the MPT is a general response to short-chain carboxylic acids or if there are critical physical chemical parameters for this response. Freshly isolated rat liver mitochondria were incubated in the presence of varying concentrations of selected carboxylic acids. All of the acids that we tested caused a concentration-dependent induction of the MPT, which was blocked by cyclosporine A. Although the C4 carboxylic acids were slightly more potent than the C5 acids, there was no correlation with the degree of saturation, the octanol/water coefficient (log P), or the dissociation constant (pKa) of the acids that we tested. We conclude that induction of the MPT in vitro is a general response to short-chain carboxylic acids having a pKa of 4 to 5.; http://www.sciencedirect.com/science/article/B6WBK-45FC9R7-T/1/dc27a6024b50dcc55a92198672d5618a

Caracterização preliminar das emissões de aldeídos e ácidos carboxílicos em veículos do ciclo Otto e do ciclo Diesel com uso de combustíveis fósseis e renováveis; Preliminary characterization of emissions of aldehydes and carboxylic acids in vehicles Otto and Diesel cycle with the use of fossil fuels and renewable

Elpidio Neto, Edson
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 01/07/2009 PT
Relevância na Pesquisa
701.93375%
O crescimento excessivo da frota veicular mundial tem feito com que milhares de toneladas de poluentes sejam lançadas na atmosfera diariamente em todo o globo, no Brasil a frota de veículos atingiu aproximadamente 54 milhões de unidades, e tem aumentado significativamente em vários estados, segundo o DETRAN (Departamento Estadual de Transito de São Paulo) o estado conta hoje com aproximadamente 19,5 milhões de veículos, 6,5 milhões só na capital, onde são emplacados aproximadamente mil veículos por dia, este crescimento tem causado episódios críticos de poluição do ar nos centros urbanos. Dentre os poluentes lançados na atmosfera de origem veicular, encontram-se os aldeídos e os ácidos carboxílicos, (objetos de estudo deste trabalho), essas substâncias são de suma importância para saúde humana, e participam nas reações fotoquímicas de formação de ozônio na baixa troposfera. Desde a implantação do PROCONVE (Programa de Controle de Poluição do Ar por Veículos Automotores) em 1988, medidas como a redução dos limites de emissão, novas tecnologias na fabricação de veículos automotores, redução da porcentagem de enxofre no diesel, combustíveis renováveis, entre outras, e programas como a Inspeção veicular na cidade de São Paulo criada a partir de 2009...

Dexametasona : interação com ácidos carboxílicos aromáticos no estado sólido; Dexamethasone : interaction with aromatic carboxylic acids in solid-state

Bergamini, Giovana
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
691.4983%
A dexametasona (DEX) está entre os glicocorticóides mais comumente descritos para uso sistêmico apresentando uma atividade gliconeogênica, imunossupressora e antiinflamatória bem difundida. Apresenta, em sua estrutura, sítios com potencial capacidade de interação com outras moléculas. Alguns ácidos carboxílicos aromáticos (ACA) e seus derivados são utilizados como excipientes em formulações farmacêuticas e também possuem grupos funcionais com propriedades potenciais de interação. Esta associação aparece, portanto, como um bom modelo de estudo para a compreensão de interações em estado sólido. Este trabalho foi desenvolvido para verificar a existência de interações, no estado sólido, da DEX com os ACA: benzóico, salicílico, 4-hidróxi-benzóico, 2,4-diidróxi-benzóico, 2,3,4-triidróxi-benzóico, gálico, 3-hidróxi-fenilacético, 3,4-diidróxi-fenilacético e isoftálico. A fim de elucidar o comportamento destes sólidos em misturas físicas binárias equiponderais foram empregadas técnicas de calorimetria exploratória diferencial (DSC), espectroscopia no infravermelho e difratometria de raios-X. A dexametasona (DEX) está entre os glicocorticóides mais comumente descritos para uso sistêmico apresentando uma atividade gliconeogênica...

Carboxylic acids of marine evaporitic oils from Sergipe-Alagoas Basin, Brazil

Rodrigues, D. C.; Koike, L.; Reis, FDM; Alves, H. P.; Chang, H. K.; Trindade, L. A.; Marsaioli, A. J.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 1209-1222
ENG
Relevância na Pesquisa
587.9983%
A. suite of 10 different marine evaporitic oil samples from Sergipe-Alagoas Basin, Brazil was studied for its biomarker content, in particular its acidic constituents. The oils showed different molecular distributions and relative abundances of n-alkanoic, isoprenoid and hopanoic acids. The observed differences were assigned to the incorporation of immature organic matter in the oils and fractionation along the migration pathway. The diagenetic precursor functionality (alcohol/ether or acid) was proposed based on the comparison of the relative abundances of the neutral and acidic biomarkers (hopanoids, isoprenoids, alkyl-steranes, monoaromatic alkyl-steroids). In the acidic fraction, 3 series of steroid-alkanoic acids and monoaromatic steroid-alkanoic acids (steroid-methanoic, ethanoic and propanoic acids and monoaromatic steroid-methanoic, ethanoic and propanoic acids) were detected, while in the neutral fraction only 2 series of each corresponding class could be observed (methyl and ethyl-steranes and monoaromatic methyl and ethyl-steroids). These carbon shifts suggest that decarboxylation is an important process in the formation of the alkyrsteranes and monoaromatic alkyl-steroids, and we infer that carboxylic acids are the diagenetic precursors of these classes of compounds. When alcohol or ether are the diagenetic precursors (isoprenoids and hopanoids)...

An easy synthesis of 3,5-disubstituted 1,2,4-oxadiazoles from carboxylic acids and arylamidoximes mediated by ethyl chloroformate

Neves Filho,Ricardo A. W.; Bezerra,Natércia M. M.; Guedes,José M.; Srivastava,Rajendra M.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2009 EN
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An efficient, clean and easy high-yielding synthesis of 3,5-disubstituted 1,2,4-oxadiazoles starting from mixed anhydrides (generated from carboxylic acids and ethyl chloroformate) and arylamidoximes is described.

Size-segregated particulate matter and carboxylic acids over urban and rural sites in Londrina City, Brazil

Freitas,Adriana de M.; Martins,Leila D.; Solci,Maria Cristina
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/05/2012 EN
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689.96625%
Samplings of atmospheric particulate matter (PM) from 0.25 to 10 µm were performed between the months of March and April 2007, simultaneously in urban and rural areas of Londrina City (Paraná State, Brazil). Results indicated that the fine fraction (PM2.5) represents a significant portion of the PM10 mass (70 and 67% in urban and rural areas, respectively). Dicarboxylic acids were found in larger concentration, contributing to the PM2.5 fraction with 78% in urban and 69% in rural areas, being oxalate and succinate the most abundant species. Mass size distribution of oxalate in urban site was presented as the dominant mode, with peaks at 0.25-0.5 µm. Acetate-to-formate mass ratio indicated the primary vehicular emissions as dominant source of carboxylic acids in Londrina. Moreover, backward trajectories indicated the transport of pollutants from São Paulo State to Londrina region.

Enantioselective synthesis of α-fluorinated β²-amino acids; Enantioselective synthesis of alpha-fluorinated beta(2)-amino acids

Edmonds, M.; Graichen, F.; Gardiner, J.; Abell, A.
Fonte: Amer Chemical Soc Publicador: Amer Chemical Soc
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
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587.24723%
A methodology for the enantioselective synthesis of α-fluorinated β²-amino acids has been developed from readily available carboxylic acids 3. Conversion to the Evan's oxazolidinone followed by enantioselective fluorination and alkylation gave 7 in high diastereomeric excess (>95%). Subsequent removal of the oxazolidinone and amination at the Bn-protected hydroxyl center gave optically active α-fluorinated β²-amino acids.; Michael K. Edmonds, Florian H. M. Graichen, James Gardiner, and Andrew D. Abell; Copyright © 2008 American Chemical Society

Intermolecular cycloaddition of nonstabilized azomethine ylides generated from 1,3-thiazolidine-4-carboxylic acids: synthesis of 5,7a-dihydro-1H,3H-pyrrolo[1,2-c]thiazoles

Cardoso, Ana L.; Kaczor, Agnieszka; Silva, Artur M. S.; Fausto, Rui; Melo, Teresa M. V. D. Pinho e; Gonsalves, António M. d'A. Rocha
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
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694.0927%
The 1,3-dipolar cycloaddition of dimethyl acetylenedicarboxylate with nonstabilized azomethine ylides, generated via the decarboxylative condensation of 1,3-thiazolidine-4-carboxylic acids with aldehydes, afforded 5,7a-dihydro-1H,3H-pyrrolo[1,2-c]thiazole derivatives. 2-Substituted-1,3-thiazolidine-4-carboxylic acids led to the stereoselective formation of 5,7a-dihydro-1H,3H-pyrrolo[1,2-c]thiazoles. Quantum-chemistry calculations were carried out allowing the rationalization of the observed stereoselective formation of the anti-dipole.; http://www.sciencedirect.com/science/article/B6THR-4KSSW69-5/1/f6fd75ae8164720ba1de8d3b3a44ed03

An easy and direct method for the synthesis of 1,2,4-triazole derivatives through carboxylic acids and hydrazinophthalazine

Rivera,Gildardo; Bocanegra-Garcia,Virgilio; Moreno,Antonio; Galiano,Silvia; Pérez,Silvia; Aldana,Ignacio; Monge,Antonio
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2008 EN
Relevância na Pesquisa
583.15586%
We have developed an easy method for the synthesis of thirteen compounds derived from 1,2,4-triazoles through a carboxylic acid and hydrazinophthalazine reaction, with a 75-85% yield mediated by the use of agents such as 1-ethyl-3-(3'-dimethylaminopropyl)-carbodiimide hydrochloride and 1-hydroxybenzotriazole. The operational simplicity of this method and the good yield of products make it valuable for the synthesis of new compounds with pharmacological activity.

Reaction of aromatic carboxylic acids with isocyanates using ionic liquids as novel and efficient media

Mallakpour,Shadpour; Yousefian,Hamed
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2007 EN
Relevância na Pesquisa
583.15586%
Ionic liquids (ILs) based on 1,3-dialkylimidazolium and ammonium have been used as an efficient reaction media in the amidation of several carboxylic acids with isocyanates. The method has wide applicability, and the protocol is mild and efficient compared to the existing methods based on conventional solvents. Proper 'design' of the ILs allows us to obtain amides in good to excellent yields. In this reaction, both aromatic and aliphatic isocyanates could be used.

Møller-Plesset perturbation theory calculations of the pK a values for a range of carboxylic acids

Namazian, Mansoor; Kalantary-Fotooh, Forogh; Noorbala, Mohammad; Searles, Debra; Coote, Michelle
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
687.3718%
This work presents calculated values of the pKa for a series of carboxylic acids spanning a wide range of acidities, using quantum mechanical treatment of solute electronic structure in conjunction with a dielectric continuum model for solvation. The calc

A mild, one-pot method for the conversion of carboxylic acids into the corresponding Weinreb amides

Banwell, Martin; Smith, Jason A
Fonte: Marcel Dekker Inc. Publicador: Marcel Dekker Inc.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
583.15586%
Reaction of various carboxylic acids with N,O-dimethylhydroxylamine under modified Mukaiyama amide coupling conditions affords the corresponding Weinerb amides in generally high yield.

The production of stable hydrophobic surfaces by the adsorption of hydrocarbon and fluorocarbon carboxylic acids onto alumina substrates

Karaman, Marilyn; Antelmi, D.; Pashley, Richard
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
691.4983%
The adsorption of various carboxylic acids onto alumina substrates has been studied as a model system for the study of the long range hydrophobic interaction. The adsorption was studied using classical adsorption isotherms, contact angle measurements and

Møller-Plesset perturbation theory calculations of the pK a values for a range of carboxylic acids

Namazian, Mansoor; Kalantary-Fotooh, Forogh; Noorbala, Mohammad; Searles, Debra; Coote, Michelle
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
695.8502%
This work presents calculated values of the pKa for a series of carboxylic acids spanning a wide range of acidities, using quantum mechanical treatment of solute electronic structure in conjunction with a dielectric continuum model for solvation. The calculations are carried out using 3rd order Møller-Plesset perturbation theory. Solute-solvent interactions have been taken into account by employing the polarizable continuum model (PCM). The calculated pKa values are in significantly better agreement with experimental data for the majority of the acids studied than other recently published results. The mean absolute deviation of the calculated pKa values is 0.68 in pKa units, for the carboxylic acids considered.

Modeling of association effects in mixtures of carboxylic acids with associating and non-associating components

Ferreira,O.; Fornari,T.; Brignole,E. A.; Bottini,S. B.
Fonte: Latin American applied research Publicador: Latin American applied research
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/07/2003 EN
Relevância na Pesquisa
687.3718%
The group contribution with association equation of state GCA-EOS has been applied to calculate thermodynamic properties of pure compounds and mixtures of carboxylic acids with paraffins, alcohols, water and gases, at low and high pressures. Two associating groups, OH and COOH, were defined. Self- and cross-association in these mixtures were quantified through two parallel COOH/COOH and OH/OH associations. The validity of this approach is supported by an excellent representation of pure compound properties (vapor pressures and compressibility factors) and phase equilibria in mixtures of (associating + inert) and (associating + associating) components at low and high pressures.

Determination of Carboxylic Acids and Water-soluble Inorganic Ions by Ion Chromatography in Atmospheric Aerosols from Tanzania

Mkoma,Stelyus L.; da Rocha,Gisele O.; de Andrade,Jailson B.
Fonte: South African Journal of Chemistry Publicador: South African Journal of Chemistry
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2014 EN
Relevância na Pesquisa
583.26066%
Atmospheric aerosol samples of PM2,5 and PM10 were collected in April-May 2011 from a rural site in Tanzania and analyzed for water-soluble inorganic ions and low molecular weight carboxylic acids using ion chromatography. PM2,5 and PM10 low-volume samplers with quartz fibre filters were deployed and aerosol collections on a 24 h basis were made for each sampler. All samples were analyzed for carboxylates and inorganic ions by using ion chromatography. The results showed that mean mass concentration of PM2,5 and PM10 were 13 ± 3.5 µg m-3 and 16 ± 2.3 µg m-3, respectively. Mean concentrations of the total carboxylates were 23.7 ± 6.5 ng m-3 in PM2.5 and 36.4 ± 12 ng m-3 in PM10 whereas total water-soluble inorganic ions were 448 ± 88 ng m-3 and 646 ± 214 ng m-3, respectively. Oxalate and malonate in PM25 and acetate in PM10 were most abundant carboxylates accounting for 64 % and 62 % of total acids, respectively. Mg2+ was most important cation in PM25 and PM10 accounting for 44 % and 24 % of total water-soluble ions, respectively, whereas SO4(2-) was the main anionic component accounting for 23 % of total ions species in PM25 and 37 % in PM10. Using source indicators, we found photochemical activities, biogenic and biomass burning could possibly be important source types for aerosols in Tanzania.