1,720,972 research outputs found
De las luciérnagas a la luz química
Full text linkLas luciérnagas nos permiten comprender el fenómeno de bioluminiscencia, es decir, la emisión de luz fría por organismos vivos. Es una reacción química que usan las luciérnagas masculinas para atraer a las femeninas y éstas responden también emitiendo luz. La reacción se da cuando la luciferina, molécula responsable de la emisión de luz, es transformada en oxiluciferina por una enzima llamada luciferasa. La luciferasa consume oxígeno y una molécula de ATP, principal fuente de energía de los seres vivos, para liberar luz a 560 nanómetros (nm). Posteriormente, el oxiluciferina, vía otras reacciones, es reciclada para formar nuevamente luciferina. De este modo es posible convertir la energía química en energía lumínica.Fil: Adam, Claudia Guadalupe. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Departamento de Química Orgánica; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Santa Fe; Argentina;Fil: Bravo, Maria Virginia. Universidad Nacional del Litoral. Facultad de Ingeniería Química; Argentina
Molecular solvent effect on the acidity constant of protic ionic liquids
Full text linkIn this work how the microscopic properties of a molecular solvent affect the chemical environment of the protic ionic liquids (PILs) was analyzed. Using Reichardt’s dye as indicator of acidity, new acidity constant values for eight PILs (pKaPILs) were determined by spectrophotometric titration. Modifying the character hydrogen bonding donor of the molecular solvent it is possible to handle the PIL acid strength. Thus, we can turn basic PILs into acidic ones thereby the molecular solvent could be used as ‘additive’ for PILs, which allowed us to tune PILs design.Fil: Adam, Claudia Guadalupe. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Bravo, Maria Virginia. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Mancini, Pedro Maximo Emilio. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Departamento de Química; Argentin
Chemical reactivity in ionic liquids: Nitroso group transfer from N-nitrososulfonamide
Full text linkNitroso group trnsfer in ionic liquids exhibits good correlation with the polarity parameters of the ionic liquid, showing that the amine nucleophililicity in no increased on going from water to the ionic liquidFil: Adam, Claudia Guadalupe. Universidad Nacional del Litoral. Instituto de Química Aplicada del Litoral. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Química Aplicada del Litoral.; ArgentinaFil: García-Río, Luis. Universidad de Santiago de Compostela; EspañaFil: Godoy, Ana. Universidad de Santiago de Compostela; EspañaFil: Leis, J. Ramón. Universidad de Santiago de Compostela; Españ
Insights on the catalytic behaviour of sulfonic acid-functionalized ionic liquids (ILs) in transesterification reactions - voltammetric characterization of sulfonic task-specific ILs with bisulfate anions
No full textThis work shows for the first time the link between the amount of free sulfuric acid (as detected by cyclic voltammetry) and the activity of sulfonic-acid-functionalized ionic liquids (ILs) as acid catalysts for a transesterification reaction, and demonstrates that sulfonic acid groups, while are not directly involved in the catalysis, release the free acid during the reaction. Two imidazolic ILs with bisulfate as the counterion and their corresponding task-specific ILs (TSILs) that resulted from the addition of a sulfonic acid group inside the imidazolic-base structure were studied. The outstanding catalytic activity at room temperature of the TSILs 1-(4-sulfonic acid)-butyl-3-methylimidazolium bisulfate ([bsmim]HSO4) and 1-(4-sulfonic acid)-butyl-imidazolium bisulfate ([bsHim]HSO4) for the transesterification ofp-nitrophenyl acetate with methanol was associated to the significant amounts of free sulfuric acid in equilibria with the ionic pairs. It was concluded that these TSILs function as reservoirs for releasing the free acid, which is the actual acid catalyst. In contrast, the corresponding non-sulfonic ILs supply very little amounts of free acid and consequently present low catalytic activities at room temperature, which in fact can be improved by increasing the reaction temperature up to 100 °C.Fil: Martini, María Belén. Universidad Nacional del Litoral. Instituto de Química Aplicada del Litoral. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Química Aplicada del Litoral.; ArgentinaFil: Fernandez, Jose Luis. Universidad Nacional del Litoral. Instituto de Química Aplicada del Litoral. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Química Aplicada del Litoral.; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; ArgentinaFil: Adam, Claudia Guadalupe. Universidad Nacional del Litoral. Instituto de Química Aplicada del Litoral. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Química Aplicada del Litoral.; Argentin
Synthesis and Self-Assembly Properties of New Surface-Active 1-Alkylimidazolium Ionic Liquids in Aqueous Media
No full textNew cationic surface-active ionic liquids (SAIL)were synthesized using 1-alkylimidazolium cations [CnHim](n = 8, 10, 12, 14, and 16) with trifluoroacetate ([CF3CO2])and methanesulfonate ([CH3SO3]) anions as counterions.Their self-aggregation behavior in water was investigatedusing electrical conductivity and fluorescence measurements.Based on the obtained results, the critical micellar concentration(CMC), the degree of counterion dissociation, α, theGibbs free energy of micelle formation, ΔG0mic, and themean aggregation number (Nagg) were determined. Theanalysis of these parameters indicates that these new SAILexhibit certain improved properties with respect to traditionalcationic surfactants. Furthermore, SAIL with[CF3CO2] counterions exhibit lower CMC values thanalkyltrimethylammonium bromide (CnTAB)-type surfactantsand their dialkylimidazolium counterparts with thesame alkyl chain length. It was demonstrated that, in thestudied SAIL, the hydrophobic probe pyrene resides deeperinside the palisade layer of the micelle and the estimatedET(30) polarity values of micellar pseudophase confirm thisresult. The abovementioned outcomes demonstrate that the1-alkylimidazolium cation is suitable to promote aggregationwhen it is accompanied by the appropriate counterions.Consequently, this contribution becomes a valuable firststep toward the potential application of these compounds asa new class of ?designed cationic surfactants.?Fil: Adam, Claudia Guadalupe. Universidad Nacional del Litoral. Instituto de Química Aplicada del Litoral. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Química Aplicada del Litoral.; ArgentinaFil: Fortunato, Graciela Guadalupe. Universidad Nacional del Litoral. Instituto de Química Aplicada del Litoral. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Química Aplicada del Litoral.; Argentin
Nitroso Group Transfer in S -Nitrosocysteine: Evidence of a New Decomposition Pathway for Nitrosothiols
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The rate of S-nitrosocysteine decomposition in a pH range between 0.7 S-nitrosocysteine, which proceeds via an intramolecular nitroso group transfer producing a primary N-nitrosamine that decomposes rapidly to give the corresponding diazonium salt. The nitroso group transfer reaction occurs intermolecularly for the decomposition pathway exhibiting a quadratic dependence on cysteine concentration. Both nitroso group transfer pathways are subject to acid catalysis by cysteine. Kinetic results indicate that the extent of S‚‚‚NO bond cleavage in the transition state is ahead of protonation of the AH‚‚‚S sulfur atom. The results obtained show the existence of a new decomposition pathway for the S-nitrosocysteine where NO is not released, and hence, it has a significant biological impact due to the potential use of nitrosothiols as NO donors.
Fil: Adam, Claudia Guadalupe. Universidad Nacional del Litoral. Facultad de Ingeniería Química; Argentina. Universidad de Santiago de Compostela; España. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: García Río, Luis. Universidad de Santiago de Compostela; EspañaFil: Leis, José Ramón. Universidad de Santiago de Compostela; EspañaFil: Ribeiro, Lara. Universidad de Santiago de Compostela; Españ
Significant effects of the anion on the catalytic behaviour of sulfonic acid-functionalized ionic liquids in transesterification reactions – A combined electrochemical/catalytic study
No full textThis work studies the strong influence of the counterion on the performance of ionic liquids (ILs) with sulfonic acid-functionalized butyl-imidazolic bases as homogeneous acid catalysts. Through a voltammetric analysis, it was shown that the availability of protons from the sulfonic acid groups in ILs with chloride and bisulphate anions is quite different, thus affecting their intrinsic activity as acid catalysts. The study was focused on the chlorides and bisulphates of 1-(4-sulfonic acid)-butyl-3-methylimidazolium ([bsmim]) and 1-(4-sulfonic acid)-butyl-imidazolium ([bsHim]), and the test reaction to evaluate these ILs as catalysts was the transesterification of p-nitrophenyl acetate with methanol. In ILs with counterion bisulphate, protons at the sulfonic acid groups are deeply involved in building the IL´s H-bonded network, so the acceptable catalytic activity for the tested reaction that was verified on these ILs was mostly sustained by the free sulphuric acid that was always present with the ionic pairs. On the contrary, ILs with chloride counterion conform more loosen networks where protons from the sulfonic acid groups are readily available and allow to efficiently catalyse the reaction, independently of the amounts of free hydrochloric acid that may be along with the ionic pair. Remarkably, the same contrast was verified in the catalytic performances of bisulphate and chloride of the non-sulfonated base 1-butyl-imidazolium ([bHim]), where the imidazolic hydrogen acted as an efficient acid catalyst only in [bHim]Cl.Fil: Martini, María Belén. Universidad Nacional del Litoral. Instituto de Química Aplicada del Litoral. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Química Aplicada del Litoral.; ArgentinaFil: Adam, Claudia Guadalupe. Universidad Nacional del Litoral. Instituto de Química Aplicada del Litoral. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Química Aplicada del Litoral.; ArgentinaFil: Fernandez, Jose Luis. Universidad Nacional del Litoral. Instituto de Química Aplicada del Litoral. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Química Aplicada del Litoral.; Argentin
Nucleophilic and acid catalyst behavior of a protic ionic liquid in a molecular reaction media. Part 1
No full textThis work presents a new approach using ionic liquids, namely ethylammonium nitrate. The aim was to analyze how the addition of small amounts of a protic ionic liquid to a pure molecular solvent, modifies the microscopic characteristics of a reaction medium. In order to achieve this, a kinetic study of nucleophilic aromatic substitution reactions between 1-fluoro-2,4-dinitrobenzene and 1-butylamine or piperidine was developed in this type of binary mixtures. We have detected nucleophiles competition originated by the presence of the ionic solvent at very low concentrations, observing the ethylamine derivative as the main substitution product. Moreover, in the light of previous results we have confirmed that the protic ionic liquid can act as both Brönsted acid and/or nucleophile. In this connection, we have selected the nucleophilic addition of amines to carbonyl compounds as reaction model. The protic ionic liquid in presence of aromatic aldehydes substituted by electron-donating groups makes possible the formation of the corresponding imines with good yields. The results demonstrated that the influence of the protic ionic liquid is very important in the course of both reaction systems.Fil: Adam, Claudia Guadalupe. Universidad Nacional del Litoral; ArgentinaFil: Fortunato, Graciela Guadalupe. Universidad Nacional del Litoral; ArgentinaFil: Mancini, Pedro Maximo Emilio. Universidad Nacional del Litoral; Argentin
Solvatochromic Dipolarity Micro-Sensor Behavior in Binary Solvent Sustems of the (Water + Ionic Liquid) Type. Application of Preferential Solvation Model And Linear Solvation Energy Relationships
Full text linkThe type of specific intermolecular and interionic interactions that are established when an ionic liquid is dissolved in water was here analysed. The study of the solvatochromic response of dipolarity micro-sensors based on Reichardt ET(30) and Kamlet?Abboud?Taft solvent scales and the application of the solvent exchangemodel confirmed the formation of different intersolvent complexes in binary mixtures of (water + [C4mim] [BF4]/[Br]) type. These complexes provide H-bond or electron pairs to the polar network, respectively. Moreover, for 4-methoxybenzenesulfonyl chloride hydrolysis reaction in the (water + [C4mim] [BF4]) system, a higher inhibition (13 times) on the kobs values was observed. Multiple linear regression analysis that allows confirming the solvent effect upon the reactive system is due to the hydrogen-bond donor properties of intersolvent complex formed. Then, the correlation between two different solvent-dependent processes proved to be successful.Fil: Adam, Claudia Guadalupe. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Bravo, Maria Virginia. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Mancini, Pedro Maximo Emilio. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Fortunato, Graciela Guadalupe. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Departamento de Química. Cátedra de Química Organica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentin
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