CHEMICAL KINETICS

Author: GONZÁLEZ SÁNCHEZ GUILLERMO.
Year: 2003.
University: ROVIRA I VIRGILI [www.urv.cat].
Place of defense: INGENIERÍA QUÍMICA.

Summary: This paper explores and describes, by kinetic models, the reactions of hidrotermólisis of lignin model compounds in water subcrítica and supercritical. Acid vainíllico and dibenzyl ether compounds were selected model to explore the thermal hydrolysis of some functional groups present in the lignin. Obtaining fuel and chemical intermediates of industrial interest from renewable resources, mainly biomass, as a promising field from the economic point of view. Likewise, the development of chemical processes that eliminate the use of expensive and toxic solvents, replacing them with compounds cheap and safe food is becoming mandatory to reduce production costs and to comply with increasingly stringent environmental standards. Reactions termohidrólisis acid in water around the critical point is investigated in a continuous tubular reactor at temperatures between 280 and 500Â ° C and pressures between 225 and 300 bar. The reactor effluent was analyzed quantitatively using high performance liquid chromatography with ultraviolet detector spectrum analysis and total organic carbon to identify products and acid vainíllico not reacted at the same time identified the compositions. The main reaction of decomposition acid vainíllico is descarboxilación to lead to the formation of 2-metoxi-fenol (guayacol). The kinetics of descarboxilación is first order with respect to the concentration of acid vainíllico. The speed of this reaction is independent of the preseión below the critical temperature and decreases with pressure in the region of supercritical temperatures. By increasing the concentration of acid vainíllico will vary the selectivity of secondary products from the decomposition of guayacol. Meanwhile, the descarboxilación acid vainílico not affected. Moreover, it was so clear that the increase of hydroxyl anion in the middle of reaction increases the speed of the path of guayacol hydrolytic reaction. Have been studied, as mentioned above, the conversion by thermal hydrolysis of dibenzyl ether in water and supercritical sub and the selectivity towards the main products of reaction. The pilot study took place in a continuous flow reactor covering a range of pressure between 225 and 362 bar, temperatures from 325 to 390Â ° C and short reaction times to minimize secondary reactions of the main products. The molar ratio between water and organic compound, w *, was set at 100 mol H2O mol DBEO -1. The effect of pressure on the speed of reaction is negligible for the subcritical temperatures, while the constant speed of different routes reaction decreased with the pressure in the region of supercritical temperatures. The volume of activation of a state of transition of these routes reaction is positive, in line with the values reported for routes reaction by free radicals as well as the mechanism SN1 for hydrolysis of ethers. There was a transition zone for supercritical temperatures, where Trigger levels have a change in magnitude.

Author: COSTAS COSTAS UGO.
Year: 2003.
University: VIGO [www.uvigo.es].
Place of defense: FACULTAD DE QUÍMICA.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: The work is this Doctoral thesis focuses on a mechanistic study of reactions of ions arenediazonio, ArN2 + with natural antioxidants such as vitamin C, VC, or acid L-ascórbico, and some of its derivatives hydrophobic, acid 6-O- octanoil L-ascórbico, VC8, acid 6-O-dodecyl-L-ascórbico, VC12 and acid 6-O-hexadecylL-ascórbico, VC16 in aqueous medium (VC and VC8) as a means micelares aniómicos and cationic (VC , VC8, VC12 and VC16). Use of micelares allows, at a microscopic level, can coexist simultaneously three distinct regions in the midst of reaction, a hydrophobic region, and the corresponding aqueous interface, which allows use as systems "módele" other more complex since accounting systems where sutratos distributed "expeditiously" on the scale of times chemical reactions típocas while making permiter one separation or concentration of reactants in a given region. The main objective is for tento, contríbuir to esclarecimineto this kind of reaction by the proposal of the reaction mechanisms by which occur, and analyze the effects provocoan systems compattimentalizados relatively senciellos as micelares on the reactivity of these substances, all for the purpose of using as a starting point for posteiroes studies in more sophisticated ways, such as the emulsions alimentos.Par development of kinetic work, and in order to have the greatest number of potential evidence to corroborate the mechanistic proposal that takes place, it has been necessary to combine the use of técinicas as espectrofotométricas (VIS.UV) chromatography (high performance liquid chromatography, HPLC) and electrochemical (polarografía differential pulse WMD). The results have revealed that the reaction between ions arildizonio and any derivatives of Vitamin C passes through a competitive mechanism that involves on the one hand, the descoposición thermal these ions (AN mechanism heterolítico DN + ) and on the other, a reaction bimolecular between these ions and ions ascorbate, which leads to the formation of an unstable Diazo ether (stage preequilibrio) at its conformation Z (kinetic control), part of which decomposes (stage lethal) leading a stable Diazo ether (E conformation, control temodinámico) and part suffers process rupture homolítica resulting derivative reduction AR-H. This mechanism is not changed by the presence of agragados micelares both cationic and anionic. La presencia de agragados micelares, tanto aniónicos como catiónicos , ha puesto de manifiesto cinéticos muy interesantes tanto sobre los valores de Kobs como en la distribución de productos de reacción.Hay que destacar que el derivado VC8 sufre, a partir de una cierta concentración,un the process of aggregation that leads to micelles VC8, which has allowed analyze cinéticamente, a system in which the very micela is reactive.

Author: CASTILLO GARCÍA MARCO.
Year: 2004.
University: COMPLUTENSE DE MADRID [www.ucm.es].
Place of defense: FACULTAD DE CIENCIAS QUÍMICAS.
Place of preparation: FACULTAD DE CIENCIAS QUÍMICAS.

Summary: In the present work has been characterized cold plasmas generated by electric shocks cells hollow cathode, NO, NO2, N2O and air pressure between 10-3 and 1 mbar, and variable conditions of gas flow and intensity of current. For this study have been used electrical probes (Langmuir probe twice), and it has been determined temperature and electron density as a function of the pressure, intensity of current, gas flow and position of the probe. We have implemented the following spectrometric techniques (the first two with temporal resolution): 1-Mass Spectrometry, for the study of ion species and stable majority. 2-dispersive spectroscopy in the visible emission, for the study of species unstable and N2 within the region luminescent plasma. 3-FTIR absorption spectroscopy. The results are compared with predictions of different versions of a single kinetic model, which they consider essential processes can take place inside the plasma. The comparison of predictions and resolute action over time allows on the one hand lower the role of a large number of physical and chemical processes, and on the other hand, estimate the coefficients of kinetic processes fundamental plasma, as is the impact dissociation mail.

Author: BAUSACH MERCADER MARTA.
Year: 2004.
University: BARCELONA [www.ub.es].
Place of preparation: FACULTAD DE QUÍMICA 8UB).

Author: MARTÍNEZ RUIZ RODRIGO.
Year: 2004.
University: LA RIOJA [www.unirioja.es].
Place of defense: UNIVERSIDAD DE LA RIOJA.
Place of preparation: UNIVERSIDAD DE LA RIOJA.

Summary: The Doctoral Thesis entitled "Characterization and ab initio study of the dynamics and kinetics of the reaction and its isotopic variations with HD and, through classic methods and quantum" is framed in the context of the dynamics of chemical reactions, which aims to field characterization microscopic level, either through the application of theoretical or experimental methods, how chemical reactions occur and how dependent the dynamic properties (scalar and vector) of the same reaction conditions. In the specific context of the Doctoral Thesis, the main objective of the same has been the theoretical study from first principles (from the electronic structure to the quantum dynamics and kinetics) of the reaction ión-molécula and its variants with isotopic and HD. This reaction, which is important in the terrestrial ionosphere and interstellar chemistry (specifically, in dense interstellar clouds, where hydrogen is mainly in the form molecular). In the first part of the report discusses the fundamentals of the ab initio methods of calculating potential energy surfaces, methods of adjusting potential energy surfaces, dynamic cuasiclásicos (method QCT) and mecano-cuánticos (exact methods (CCH) and propagating wave packets (Wave Packet, WP)). The second part presents the results of the thesis work itself using the theoretical methods described in the first part of the report. Subsequently, indicating the findings of the work, completing the report with two appendices. The first provides dynamic and kinetic information in tabular form and the second describes the input files for the two programs dynamics mecano-cuántica employees.

Author: AMOEDO CABALEIRO FRANCISCO ANDRÉS.
Year: 2005.
University: SANTIAGO DE COMPOSTELA [www.usc.es].
Place of defense: FACULTAD DE QUÍMICA.
Place of preparation: FACULTAD DE QUÍMICA.

Summary: This paper presents a study kinetic and thermodynamic that can be divided into three parts, the first of the formation of derivatives N-cloro-heterociclos such as N-Cl-pirrolidina, N-Cl-pirrolidona, N Cl-succinimida, N-Cl-2-oxazolidona and N-Cl-5 ,5-dimetiloxazolidina-2 ,4-diona from the corresponding compounds hetero making them react hiploclorito sodium. A second part where he studied the formation of the N-Cl-2-oxazolidona with other actors clorantes including N-Cl-succinimida (NCS), terc-butillhípoclorito, Tricloromelamina, N-Cl-diisopropilamina. Once the training conditions of the N-Cl-oxazolidona, and established its stability, it moves to the third stage where he is studying reactivity of the N-Cl-oxazolidona with bulls importance chemical ions such as iodide, bromide, thiocyanate and nitrite. In all cases establishing an equation for calculating the speed orders reaction by the method of isolation, and after we calculate the rate constant. It also explores the factors that can influence the reaction medium as the ionic strength, pH and temperature, and then finally proposed a mechanism to justify the experimental values obtained in all cases the mechanism that justifies each of the experimental values. The study was performed in simple aqueous systems and working methodology is based primarily on monitoring espectrofotomérico conventional (UV-Vis), and in the case of quick reactions used techniques espectrofotométricas flow stopped.

Author: FUENTES ORTEGA MATILDE ESTHER.
Year: 2005.
University: CASTILLA-LA MANCHA [www.uclm.es].
Place of defense: ESCUELA POLITECNICA.
Place of preparation: UNIVERSIDAD DE CASTILLA LA MANCHA.

Summary: This memory has done an analysis of two kinetic processes activation zimógenos, which have been applied to two enzyme systems of physiological interest such as enzyme system pepsinógeno-pepsina and enzyme system plasminógeno-plasmina, remain in our view, a very useful tool in the study of kinetic reactions limited proteolysis, key in regulating metabolism. To provide a theoretical basis for future kinetic studies, experimental and theoretical, it is important to analyze the behavior of kinetic processes of self-zimógenos from a general point of view. To that end, it has proposed a general model of self-zimógenos for aspartic proteases, which is good enough in general to be applied to the experimental kinetic study of the self from different zimógenos including routes activation intramolecular and intermolecular. The model has been studied for two different forms of monitoring pilot of the reaction: in discontinuous and continuous thanks to a coupling reaction cromogénica. Have also been obtained for the first time adimensionales parameters for determining the relative contribution of routes activation intramolecular and intermolecular the activation process autocatalítica of zimógenos. This has been illustrated by the experimental self-monitoring of pepsinógeno to pepsin. It also has studied a model specific activation zimógenos corresponding to the mechanism of activation of plasminogen to plasmin by streptokinase conducting the study limitations under less restrictive and more reasonable to those used previously in the scientific literature.

Author: FERRIT MARTÍN MÓNICA.
Year: 2005.
University: GRANADA [www.ugr.es].
Place of defense: FACULTAD DE FARMACIA.
Place of preparation: FACULTAD DE FARMACIA.

Summary: The research contained in this report Doctoral Thesis has focused primarily: 1, - In a study of the reaction kinetic spectrophotometric alkaline hydrolysis of two antiplatelet drugs derived from salicylic acid: acetylsalicylic acid (aspirin) and acid 2-acetoxi -4 - trifluorometilbenzóico (Triflusal); both the absence and presence of various systems micelares, with the aim of establishing the influence the group trifluorometilo on that reaction. 2-Amid micelar to establish the influence of the nature of surfactant, which is able to establish such a system and the effects micelares according to the following factors: A-Burden of micela. B-Contraión of micela. C-size polar head group surfactant. D-length chain apolar hydrocarbon. Have been selected surfactants: hydroxide cetiltrimetilamonio (CTAOH) chloride cetiltrimetilamonio (CTACI) bromide cetiltrimetilamonio (CTABr) bromide tetradeciltrimetilamonio (TTABr) bromide dodeciltrimetilamonio (DoTABr) bromide etilhexadecildimetilamonio (CDEABr), sodium lauryl (LSNa) propanosulfonato of hexadeciltrimetilamonio (SB3-16), propane sulfonate tetradeciltrimetilamonio (SB3-14) propanosulfonato of doceiltrimetilamonio (SB3-12) and Polyoxyethylene (23) laurileter (Brij 35). E-It is also interest in studying the effect of high concentrations of contraión of micela or even other contraiones therefore has relaizado the reaction of alkaline hydrolysis in the presence of different salts such as sodium acetate, sodium chloride and sodium bromide . F - has been well studied, the effect exerted concentration nucleófilo, which have analyzed all the reactions to various concentrations of sodium hydroxide. 3-To ensure an adequate analysis of the experimental data have been identified physicochemical properties of surfactants genetic study in the same conditions reaction using a method conductimétrico. The properties of interest were: concentration micelar critical degree of ionization micelar and fraction surface micelar neutralized.

Author: TEJERO VILLAGRASA ISMAEL.
Year: 2006.
University: AUTÓNOMA DE BARCELONA [www.uab.es].
Place of defense: CENTRO NACIONAL DE MICROELECTRONICA.
Place of preparation: DEPARTAMENTO DE QUÍMICA - UNIVERSIDAD AUTÓNOMA DE BARCELONA.

Summary: The oxidative degradation of fats known since the antigà ¼ age. In contrast, the existence and relevance of the species radicalarias oxygen was not recognized until half of the last century. The lipid peroxidation has become an area of research in continuous growth, both in medicine and biology because of the relationship with chronic type neurodegenerative and cardiovascular. These reactions of oxidation can occur through three kinds of mechanisms: (i) encimático (ii) not radicalario not encimático and (iii) radicalario not encimático. Several aspects of the chemical kinetics of these processes have been studied from a viewpoint teórico-químico, throughout this thesis.

Author: PEÑACOBA MAESTRE INDALECIO ANTONIO.
Year: 2006.
University: BURGOS [www.ubu.es].
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: This work falls within the line of research with quick reactions biopolymers Area Physical Chemistry, Department of Chemistry at the UBU, and the Department of Chimica e Chimica Industriale from the University of Pisa. The seroalbúmina among its physiological functions, has an important role in the osmotic pressure of colloidal blood and aid in the transportation, distribution and metabolism of several ligands. These ligands represent wide range of endogenous and exogenous substances, including fatty acids, amino acids (mainly tryptophan and cysteine), esteriodes, metals such as Ca (II), Cu (II) and Zn (II), and numerous medications. This globular protein, since the nineteenth century, is known as a component of the blood, so from the beginning of the modern research has generated considerable interest. Nonetheless, the peculiar nature due to its high flexibility and adaptability configuracional still presents a partial picture in some respects. Linking the sulfonftaleínas with seroalbúmina has important physiological and clinical applications such as the analysis of proteins and determining the concentration of binding sites of serum bilirubin. The investigation into the detailed mechanism of the link may provide a better basis for such procedures. The study of the liaison mechanism of four substances sulfonftaleínicas, bromothymol blue (BTB), of xylenol orange (XO), Red glicincresol (GCR) and Blue glicintimol (GTB) with the bovine seroalbúmina (BSA), has been carried out by experiments static and kinetic generated by the variation of the spectrum when these ligands bind to the protein. Techniques used to elucidate the kinetic mechanism are based on chemical relaxation (jump in temperature or pressure) or withheld flow ( "stopped-flow"). Part kinetic took place with a team of chemical relaxation by jumping temperature ( "T-jump"). Moreover, the study static through spectroscopy UV-vis was supplemented with measures circular dichroism (CD) that give information on the structures of complexes in the different experimental conditions. The parameters liaison BSA-sulfoftaleínas, No numbers union in protein and Ka constant association has been calculated based on the valuations spectral UV-visible. Furthermore, the thermal stability of the complex BSA-BTB, has been studied through distortion. Despite the apparent disparity in the results obtained for the interaction of BSA with BTB and other ligands, XO, GCR and GTB, a unique kinetic mechanism. In this process the isomeric forms of the protein-dependent pH, play an important role.

Author: MONEDERO VILLALBA M. ESPERANZA.
Year: 2006.
University: CASTILLA-LA MANCHA [www.uclm.es].
Place of defense: FACULTAD DE CIENCIAS QUIMICAS.
Place of preparation: UNIVERSIDAD DE CASTILLA LA MANCHA.

Summary: In the low troposphere, volatile organic compounds (VOCs) emitted into the atmosphere suffer degradation processes, such as fotólisis and oxidation reactions. In the latter case, photochemical reactions are initiated by the attack on the OH radical of VOCs during the day, the radical NO3 overnight, ozone both by day and by night and Cl atoms of which play an locally important role in maritime and coastal zones during the day. The aldehyde compounds are very important in the chemistry of the atmosphere. They are cast as a primary pollutant from the incomplete combustion of fossil fuels or biogenic emissions, or as a secondary pollutants from previous reactions taking place in the atmosphere. Most of them are intermediate forced the fotooxidación of most organic compounds from the atmosphere. We have measured high concentrations of these compounds in areas contaminated as a result of emsiones anthropogenic as traffic or industrial activity. To all this must be added the fact that some aldehydes are already toxic in themselves produce irritation in eyes and lungs. Moreover, some of the secondary compounds formed from the aldehydes, especially nitrate peroxiacilo, PANs, are much more dangerous since they are phytotoxic, mutagenic, are a source of NOx in the troposphere and contribute to the formation of O3 and both the photochemical smog. So in this thesis has been studied atmospheric oxidation of various saturated and unsaturated aldehydes with radical nitrate. The kinetic study has been carried out using a discharge tube flow using Laser Induced Fluorescence (LIF) detection system, in the range of temperatures 249-298 K and pressure 1 torr, obtaining both constant speed as Arrhenius parameters of these reactions. The study was conducted using products reactor glass pirex analysis on the spot through an infrared spectrometer with Fourier transform. (FTIR) (298 ± 2) K and atmospheric pressure. The result has been identified generating some nitrates peroxiacilo, PANs, due to the reaction of aldehydes with nitrate radical studied. Using the spectra obtained in identifying products have been calculated absolute sections effective and integrated these PANs.