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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
36.1%
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.

Group contribution modeling of activity coefficients in associating solutions containing water, alcohols and carboxylic acids

Ferreira, Olga; Orge, Beatriz; Foco, Gloria; Bottini, Susana B.
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
36.07%
A modified UNIFAC group contribution model for the prediction of activity coefficients in associating solutions (A-UNIFAC) is applied to calculate phase equilibria in binary and ternary mixtures of associating and non-associating species, including alcohols, water, carboxylic acids, esters, alkanes, aromatic hydrocarbons and alkyl chlorides. Self- and cross-association in these mixtures is adequately described by the definition of a single hydrogen-bonding group. The new model is able to give good predictions of vapor-liquid equilibria, liquid-liquid equilibria and infinite dilution activity coefficients, using a single set of group-interaction parameters.

Infrared-induced conformational interconversion in carboxylic acids isolated in low-temperature rare-gas matrices

Maçôas, Ermelinda M. S.; Khriachtchev, Leonid; Pettersson, Mika; Lundell, Jan; Fausto, Rui; Räsänen, Markku
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
Relevância na Pesquisa
36.03%
An overview of our recent studies dealing with infrared-induced conformational interconversion of carboxylic acids isolated in rare-gas matrices is presented. Extensive rotational photoisomerization studies have been performed on formic acid, which is the simplest organic acid enabling this kind of processes. Formic acid has two conformers and interconversion between them can be induced by vibrational excitation. As such, it is an ideal model system to study the conformational dynamics of the carboxylic group. Formic acid molecules were found to be isolated in different local environments within the rare-gas matrices, as shown by the site splitting of the vibrational bands. Narrowband tunable infrared (IR) radiation was used to induce site-selective isomerization processes. The induced changes in the IR absorption spectra allowed for a detailed analysis of the vibrational properties of both conformers of formic acid isolated in solid argon. In particular, derived from the intermode coupling constants the local environment was shown to affects the intramolecular potential energy surface. Tunneling is involved in the rotamerization of formic acid, with the tunneling rate being affected by the local environment. Additionally, formic acid exhibits isomer-selective photodissociation where narrowband IR excitation can control the conformer-dependent photodissociation channels. Tunable IR radiation was also used to promote rotamerization in a series of matrix-isolated dicarboxylic acids (ethanedioic...

Rotational isomerization of small carboxylic acids isolated in argon matrices: Tunnelling and quantum yields for the photoinduced processes

Maçôas, Ermelinda M. S.; Khriachtchev, Leonid; Pettersson, Mika; Fausto, Rui; Räsänen, Markku
Fonte: Royal Society of Chemistry Publicador: Royal Society of Chemistry
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
35.92%
The quantum yields for internal rotation around the C–O bond induced by excitation of the first overtone of the hydroxyl stretching mode in formic, acetic, and propionic acids isolated in solid Ar are comparatively discussed. The tunnelling kinetics for isomerization from the higher energy arrangement of the carboxylic group (cis) to the lower energy arrangement (trans) in this series of compounds is also analysed. Finally, the quantum yield for the Cα–C isomerization in propionic acid was investigated and, in contrast with the C–O isomerization, shown to be probably sensitive to the local matrix morphology.

Synthesis and structural characterization of a new polymeric zinc(II) complex with thiophene-2-carboxylic acid

CAGNIN, F.; CASTELLANO, Eduardo Ernesto; DAVOLOS, M. R.
Fonte: TAYLOR & FRANCIS LTD Publicador: TAYLOR & FRANCIS LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.09%
A new polymeric zinc(II) complex with thiophene-2-carboxylic acid (-tpc) of composition [Zn2(C20H12O8S4)]n was obtained and structurally characterized by X-ray diffraction, thermal analysis, nuclear magnetic resonance (NMR), and infrared spectroscopies. Upfield shift in the 1H-NMR spectrum is explained by the crystalline structure, which shows the thiophene rings overlapping each other in parallel pairs. The compound crystallizes in the monoclinic system, space group P21/c, with a = 9.7074(4) angstrom, b = 13.5227(3) angstrom, c = 18.9735(7) angstrom, = 95.797(10)degrees, and Z = 4. Three -tpc groups bridge between two Zn(II) ions through oxygens and the fourth one bridges between one of these ions and the third one, symmetry related by a twofold screw axis. This arrangement gives rise to infinite chains along the crystallographic a direction. The metal atoms display an approximate tetrahedral configuration. The complex is insoluble in water, ethanol, and acetone, but soluble in dimethyl sulfoxide.; FAPESP[2007/06072-2]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); CNPq; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Eletrossíntese e caracterização de filmes de polipirrol-2-ácido carboxílico para uso em biossensores amperométricos construídos em eletrodos miniaturizados; Electrosynthesis and characterizations of polypyrrole-2-carboxylic acid for application as amperometric biosensor constructed in microelectrodes

Foschini, Mauricio
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 05/06/2009 PT
Relevância na Pesquisa
46.21%
Neste trabalho, apresentamos a eletrossíntese de um novo polímero condutor derivado do polipirrol (PPI) funcionalizado com um grupo carboxílico, o polipirrol-2-ácido carboxílico (PPI-2-COOH), e o seu uso como transdutor amperométrico em biossensores pelo uso da polifenol oxidase (PFO). São apresentadas todas as etapas de síntese e de caracterização dos filmes poliméricos em microeletrodos e o preparo e a resposta dos biossensores montados para a detecção de um composto fenólico. Nossos estudos sobre eletrossíntese, respostas eletroquímicas dos filmes, juntamente com resultados de microgravimetria e modelagem molecular de dímeros e trímeros derivados de PI-2-COOH, permitiram com que pudéssemos sugerir pela primeira vez um mecanismo de eletropolimerização deste monômero em meio não aquoso. Na caracterização dos filmes por espectroscopia in situ no UV-visível e infravermelho próximo foram observadas duas bandas idênticas às transições pi-pi* características dos filmes de PPI no seu estado neutro e de maior dopagem, confirmando a possibilidade de haver duas conformações na cadeia do PPI-2-COOH. Com a modelagem molecular de um oligômero formado a partir da oxidação do PI-2-COOH, verificamos que para cada 4 anéis heterocíclicos acoplados entre si na posição 4-5...

Síntese e caracterização de macromoléculas do tipo Poli(Ácido carboxílico)-Poli(Eter-poliol) com propriedades termoplásticas e termorrígidas e avaliação de propriedades mecânicas cerâmicos à base de caulim.; Synthesis and characterization of macromolecules of the type of poly (carboxylic acid)-poly(ether polyol) with thermoplastic and thermoset properties and evaluation of mechanical properties of ceramics materials based on kaolin.

Rodrigues, José Carlos
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 27/08/2009 PT
Relevância na Pesquisa
36.09%
Este trabalho apresenta o estudo de um sistema polimérico bi-componente formado por Poli(Ácido carboxílico)-Poli(Eter-poliol), constituído primariamente de um polímero acrílico polimerizado pelo processo de polimerização em solução aquosa por mecanismo de radicais livres ao qual foi adicionado seqüencialmente, um Poli(Eter-poliol), ambos de baixo peso molecular médio. Tal sistema tem por finalidade atuar como dispersante-ligante em sistema cerâmico à base de caulim CADAM, uma vez que este sistema apresenta propriedades termoplásticas e termorrígidas a diferentes temperaturas. Foram sintetizados 03 protótipos de um sistema polimérico e o critério para escolha teve como base o pH do sistema em sentido generalizado, isto é, compreendendo as diversas fases de preparação dos polímeros e sua aplicação final. É do conhecimento comum que a reação de esterificação entre grupos COOHOH requer catálise ácida para ocorrer, o qual usualmente é realizada em pH abaixo de 4 e, neste ensaio, este pH ácido é devido à presença de ácido para-toluenosulfônico, que atua como catalisador de esterificação. Em tal intervalo de pH, em virtude do ponto isoelétrico do caulim ser comumentemente abaixo de 4...

Synthesis and structural characterization of a new polymeric zinc(II) complex with thiophene-2-carboxylic acid

Cagnin, F.; Castellano, E. E.; Davolos, M. R.
Fonte: Taylor & Francis Ltd Publicador: Taylor & Francis Ltd
Tipo: Conferência ou Objeto de Conferência Formato: 2278-2285
ENG
Relevância na Pesquisa
36.03%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Processo FAPESP: 07/06072-2; A new polymeric zinc(II) complex with thiophene-2-carboxylic acid (-tpc) of composition [Zn2(C20H12O8S4)]n was obtained and structurally characterized by X-ray diffraction, thermal analysis, nuclear magnetic resonance (NMR), and infrared spectroscopies. Upfield shift in the 1H-NMR spectrum is explained by the crystalline structure, which shows the thiophene rings overlapping each other in parallel pairs. The compound crystallizes in the monoclinic system, space group P21/c, with a = 9.7074(4) angstrom, b = 13.5227(3) angstrom, c = 18.9735(7) angstrom, = 95.797(10)degrees, and Z = 4. Three -tpc groups bridge between two Zn(II) ions through oxygens and the fourth one bridges between one of these ions and the third one, symmetry related by a twofold screw axis. This arrangement gives rise to infinite chains along the crystallographic a direction. The metal atoms display an approximate tetrahedral configuration. The complex is insoluble in water, ethanol, and acetone, but soluble in dimethyl sulfoxide.

Carbon nanotube-reinforced siloxane-PMMA hybrid coatings with high corrosion resistance

Hammer, P.; Dos Santos, F. C.; Cerrutti, B. M.; Pulcinelli, S. H.; Santilli, C. V.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 601-608
ENG
Relevância na Pesquisa
35.92%
Siloxane-polymethyl methacrylate hybrid films containing functionalized multiwall carbon nanotubes (CNTs) were deposited by dip-coating on carbon steel substrates from a sol prepared by radical polymerization of methyl methacrylate and 3-methacryloxy propyl-trimethoxysilane, followed by hydrolytic co-polycondensation of tetraethoxysilane. The correlation between the structural properties and corrosion protection efficiency was studied as a function of the molar ratio of nanotubes carbon to silicon, varied in the range between 0.1% and 5%. 29Si nuclear magnetic resonance and thermogravimetric measurements have shown that hybrids containing carbon nanotubes have a similar degree of polycondensation and thermal stability as the undoped matrix and exhibit and excellent adhesion to the substrate. Microscopy and X-ray photoelectron spectroscopy results revealed a very good dispersion of carbon nanotubes in the hybrid matrix and the presence of carboxylic groups allowing covalent bonding with the end-siloxane nodes. Potentiodynamic polarization curves and electrochemical impedance spectroscopy results demonstrate that CNTs containing coatings maintain the excellent corrosion protection efficiency of the hybrids, showing even a superior performance in acidic solution. The nanocomposite structure acts as efficient corrosion barrier...

Specificity of dopachrome tautomerase and inhibition by carboxylated indoles. Considerations on the enzyme active site.

Aroca, P; Solano, F; Garcia-Borrón, J C; Lozano, J A
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/07/1991 EN
Relevância na Pesquisa
26.34%
Dopachrome tautomerase (EC 5.3.2.3) catalyses the tautomerization of dopachrome to 5,6-dihydroxyindole-2-carboxylic acid (DHICA) within the melanin-formation pathway. We have analysed a series of substrate analogues and related compounds as possible substrates and inhibitors of tautomerization. The enzyme appears to be highly specific since D-dopachrome, alpha-methyldopachrome, dopaminochrome, adrenochrome methyl ether and deoxyadrenochrome are not substrates. Conversely, dopachrome tautomerase catalyses the tautomerization of dopachrome methyl ester, suggesting that a carboxy group, either free or as a methyl ester, is essential for enzyme recognition. No inhibition of dopachrome tautomerization was observed in the presence of either semiquinonic compounds, such as tropolone and L-mimosine, or pyrrole-2-carboxylic acid and unsubstituted indole. However, a number of indole derivatives, including DHICA, the product of dopachrome tautomerization, and the analogues 5-hydroxyindole-2-carboxylic and indole-2-carboxylic acid were able to inhibit the enzyme. Furthermore, indoles with a side chain at position 3 of the ring and containing a carboxylic group at the gamma-position of this chain, such as L-tryptophan or indole-3-propionic acid...

The size of hydroxyl groups in solution and the changes in size associated with the ionization of phenolic, carboxylic and amino groups in phenolic quaternary ammonium salts, nicotine and some amino acids: possible implications for drug-water and drug-receptor interactions.

Barlow, R. B.
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em //1980 EN
Relevância na Pesquisa
35.83%
Size in solution can be expressed either as the apparent molal volume at infinite dilution (phi 0v) amd the concentration parameter (j) or as the partial molal volume of the solute at infinite dilution (V0(2)) and the concentration parameter for the solute or solvent (qs or qw). Although calculated differently, these are derived from the same results and are equivalent. From measurement with phenolic quaternary ammonium salts, including compounds with high nicotine-like activity, the apparent size of the hydroxyl group in water is small and variable. Phenolic groups are slightly larger than alcoholic groups, which should be better hydrogen donors. By measuring the volume change associated with ionisation it is possible to measure the size of charged groups such as phenate and carboxylate; these are much smaller than phenolic and carboxyl. Ammonium groups, however, are only slightly smaller than the corresponding amines. The zwitterion forms of amino acids are associated with a minimum in volume but the volume changes increase with chain length from glycine to gamma-aminobutyric acid. Groups separated by less than this distance interact in their effects on water. Decreases in volume or unexpectedly small increments in apparent molal volume represent decreases in entropy which must be taken into account in drug-water-receptor interactions. Although they may be offset by enthalpy changes...

The effects of a series of omega-phosphonic alpha-carboxylic amino acids on electrically evoked and excitant amino acid-induced responses in isolated spinal cord preparations.

Evans, R. H.; Francis, A. A.; Jones, A. W.; Smith, D. A.; Watkins, J. C.
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em /01/1982 EN
Relevância na Pesquisa
35.92%
1 The depressant actions on evoked electrical activity and the excitant amino acid antagonist properties of a range of omega-phosphonic alpha-carboxylic amino acids have been investigated in the isolated spinal cord preparations of the frog or immature rat. 2 When tested on dorsal root-evoked ventral root potentials, members of the homologous series from 2- amino-5-phosphonovaleric acid to 2-amino-8-phosphonooctanoic acid showed depressant actions which correlated with the ability of the substances to antagonize selectivity motoneuronal depolarizations induced by N-methyl-D-aspartate. 3 2-Amino-5-phosphonovalerate was the most potent substance of the series giving an apparent KD of 1.4 microM for the antagonism of responses to N-methyl-D-aspartate. 4 A comparison of the (+)- and (-)-forms of 2-amino-5-phosphonovalerate indicated that the N-methyl-D-aspartate antagonist activity and the neuronal depressant action of this substance were both due mainly to the (-)-isomer. 5 The (-)- and (+)-forms of 2-amino-4-phosphonobutyrate had different actions. The (-)-forms of this substance had a relatively weak and non-selective antagonist action on depolarizations induced by N-methyl-D-aspartate, quisqualate and kainate and a similarly weak depressant effect when tested on evoked electrical activity. The (+)-form was more potent than he (-)-form in depressing electrically evoked activity but did not antagonize responses to amino acid excitants. At concentrations higher than those required to depress electrically evoked activity...

Cyclopentane-1,3-dione: A Novel Isostere for the Carboxylic Acid Functional Group. Application to the Design of Potent Thromboxane (A2)-Receptor Antagonists

Ballatore, Carlo; Soper, James; Piscitelli, Francesco; James, Michael; Huang, Longchuan; Atasoylu, Onur; Huryn, Donna M.; Trojanowski, John Q.; Lee, Virginia M.-Y.; Brunden, Kurt R.; Smith, Amos B.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
26.3%
Cyclopentane-1,3-diones are known to exhibit pKa values typically in the range of carboxylic acids. To explore the potential of the cyclopentane-1,3-dione unit as a carboxylic acid isostere, the physical-chemical properties of representative congeners were examined and compared with similar derivatives bearing carboxylic acid or tetrazole residues. These studies suggested that cyclopentane-1,3-diones may effectively substitute for the carboxylic acid functional group. To demonstrate the use of the cyclopentane-1,3-dione isostere in drug-design, derivatives of a known thromboxane-A2 prostanoid (TP) receptor antagonist, 3-(3-(2-(4-chlorophenylsulfonamido)ethyl)-phenyl)propanoic acid (12), were synthesized and evaluated in both functional and radioligand-binding assays. A series of mono- and di-substituted cyclopentane-1,3-dione derivatives (41–45) were identified that exhibit nM IC50 and Kd values similar to 12. Collectively, these studies demonstrate that the cyclopentane-1,3-dione moiety comprises a novel isostere of the carboxylic acid functional group. Given the combination of the relatively strong acidity, tunable lipophilicity, and versatility of the structure, the cyclopentane-1,3-dione moiety may constitute a valuable addition to the palette of carboxylic acid isosteres.

Novel 5-substituted benzyloxy-2-arylbenzofuran-3-carboxylic acids as calcium activated chloride channel inhibitors

Kumar, Satish; Namkung, Wan; Verkman, A. S.; Sharma, Pawan K.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
36.03%
Transmembrane protein 16A (TMEM16A) channels are recently discovered membrane proteins that functions as a calcium activated chloride channel (CaCC). CaCCs are major regulators of various physiological processes, such as sensory transduction, epithelial secretion, smooth muscle contraction and oocyte fertilization. Thirty novel 5-substituted benzyloxy-2-arylbenzofuran-3-carboxylic acids (B01–B30) were synthesized and evaluated for their TMEM16A inhibitory activity by using short circuit current measurements in Fischer rat thyroid (FRT) cells expressing human TMEM16A. IC50 values were calculated using YFP fluorescence plate reader assay. Final compounds, having free carboxylic group displayed significant inhibition. Eight of the novel compounds B02, B13, B21, B23, B25, B27, B28, B29 exhibit excellent CaCCs inhibition with IC50 value <6 μM, with compound B25 exhibiting the lowest IC50 value of 2.8 ± 1.3 μM. None of the tested ester analogs of final benzofuran derivatives displayed TMEM16A/CaCCs inhibition.

The carboxyl group of Glu113 is required for stabilization of the diferrous and bis-FeIV states of MauG

Tarboush, Nafez Abu; Yukl, Erik T.; Shin, Sooim; Feng, Manliang; Wilmot, Carrie M.; Davidson, Victor L.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
35.79%
The diheme enzyme MauG catalyzes a six-electron oxidation required for posttranslational modification of a precursor of methylamine dehydrogenase (preMADH) to complete the biosynthesis of its protein-derived tryptophan tryptophylquinone (TTQ) cofactor. Crystallographic studies have implicated Glu113 in the formation of the bis-FeIV state of MauG, in which one heme is FeIV=O and the other is FeIV with His-Tyr axial ligation. An E113Q mutation had no effect on the structure of MauG, but significantly altered its redox properties. E113Q MauG could not be converted to the diferrous state by reduction with dithionite, but was only reduced to a mixed valence FeII/FeIII state, which is never observed in wild-type (WT) MauG. Addition of H2O2 to E113Q MauG generated a high valence state that formed more slowly and was less stable than the bis-FeIV state of WT MauG. E113Q MauG exhibited no detectable TTQ biosynthesis activity in a steady-state assay with preMADH as the substrate. It did catalyze the steady-state oxidation of quinol MADH to the quinone, but 1000-fold less efficiently than WT MauG. Addition of H2O2 to a crystal of the E113Q MauG-preMADH complex resulted in partial synthesis of TTQ. Extended exposure of these crystals to H2O2 resulted in hydroxylation of Pro107 in the distal pocket of the high-spin heme. It is concluded that the loss of the carboxylic group of Glu113 disrupts the redox cooperativity between hemes that allows rapid formation of the diferrous state...

Highly stereoselective biosynthesis of (R)-α-hydroxy carboxylic acids through rationally re-designed mutation of d-lactate dehydrogenase

Zheng, Zhaojuan; Sheng, Binbin; Gao, Chao; Zhang, Haiwei; Qin, Tong; Ma, Cuiqing; Xu, Ping
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 02/12/2013 EN
Relevância na Pesquisa
36.09%
An NAD-dependent d-lactate dehydrogenase (d-nLDH) of Lactobacillus bulgaricus ATCC 11842 was rationally re-designed for asymmetric reduction of a homologous series of α-keto carboxylic acids such as phenylpyruvic acid (PPA), α-ketobutyric acid, α-ketovaleric acid, β-hydroxypyruvate. Compared with wild-type d-nLDH, the Y52L mutant d-nLDH showed elevated activities toward unnatural substrates especially with large substitutes at C-3. By the biocatalysis combined with a formate dehydrogenase for in situ generation of NADH, the corresponding (R)-α-hydroxy carboxylic acids could be produced at high yields and highly optical purities. Taking the production of chiral (R)-phenyllactic acid (PLA) from PPA for example, 50 mM PPA was completely reduced to (R)-PLA in 90 min with a high yield of 99.0% and a highly optical purity (>99.9% e.e.) by the coupling system. The results presented in this work suggest a promising alternative for the production of chiral α-hydroxy carboxylic acids.

LC-MS/MS analysis of 2-aminothiazoline-4-carboxylic acid as a forensic biomarker for cyanide poisoning

Yu, Jorn CC; Martin, Sarah; Nasr, Jessica; Stafford, Katelyn; Thompson, David; Petrikovics, Ilona
Fonte: Baishideng Publishing Group Co., Limited Publicador: Baishideng Publishing Group Co., Limited
Tipo: Artigo de Revista Científica
Publicado em 26/10/2012 EN
Relevância na Pesquisa
35.92%
AIM: To demonstrate the potential of using 2-aminothiazoline-4-carboxylic acid (ATCA) as a novel biomarker/forensic biomarker for cyanide poisoning.

Cationic mononuclear ruthenium carboxylates as catalyst prototypes for self-induced hydrogenation of carboxylic acids

Naruto, Masayuki; Saito, Susumu
Fonte: Nature Pub. Group Publicador: Nature Pub. Group
Tipo: Artigo de Revista Científica
Publicado em 28/08/2015 EN
Relevância na Pesquisa
36.16%
Carboxylic acids are ubiquitous in bio-renewable and petrochemical sources of carbon. Hydrogenation of carboxylic acids to yield alcohols produces water as the only byproduct, and thus represents a possible next generation, sustainable method for the production of these alternative energy carriers/platform chemicals on a large scale. Reported herein are molecular insights into cationic mononuclear ruthenium carboxylates ([Ru(OCOR)]+) as prototypical catalysts for the hydrogenation of carboxylic acids. The substrate-derived coordinated carboxylate was found to function initially as a proton acceptor for the heterolytic cleavage of dihydrogen, and subsequently also as an acceptor for the hydride from [Ru–H]+, which was generated in the first step (self-induced catalysis). The hydrogenation proceeded selectively and at high levels of functional group tolerance, a feature that is challenging to achieve with existing heterogeneous/homogeneous catalyst systems. These fundamental insights are expected to significantly benefit the future development of metal carboxylate-catalysed hydrogenation processes of bio-renewable resources.

Selective Nickel- and Manganese-Catalyzed Decarboxylative Cross Coupling of Some α,β-Unsaturated Carboxylic Acids with Cyclic Ethers

Zhang, Jia-Xiang; Wang, Yan-Jing; Zhang, Wei; Wang, Nai-Xing; Bai, Cui-Bing; Xing, Ya-Lan; Li, Yi-He; Wen, Jia-Long
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 12/12/2014 EN
Relevância na Pesquisa
35.92%
A nickel- and manganese-catalyzed decarboxylative cross coupling of α, β-unsaturated carboxylic acids with cyclic ethers such as tetrahydrofuran and 1, 4-dioxane was developed. Oxyalkylation was achieved when nickel acetate was used as catalyst, while manganese acetate promoted the reaction of alkenylation.

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
36.1%
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.