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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
291

Reação de 'alfa'-amidoalquilação de ions N-aciliminio com nucleofilos de carbono em sistema micelar SDS/agua, na ausencia de solvente e em liquido ionico : aplicação na sintese de um analogo da febrifugina / 'alfa'-amidoalkylation of N-acyliminium ions with carbon nucleophiles in SDS/water, under solvent-free condition and in ionic liquid. Aplication to the synthesis of a febrifugine analog

Camilo , Nilton Soares 31 August 2006 (has links)
Orientador: Ronaldo Aloise Pilli / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-07T21:45:34Z (GMT). No. of bitstreams: 1 Camilo_NiltonSoares_D.pdf: 3180029 bytes, checksum: 2847c04256e604434393243a35c4298a (MD5) Previous issue date: 2006 / Doutorado / Quimica Organica / Doutor em Ciências
292

O papel estrutural de cossolutos derivados de cinamato para a formação de micelas gigantes de surfactantes catiônicos / The structural role of cossolutes derived from cinnamate on the formation of cationic surfactant wormlike micelles

Clinckspoor, Karl Jan, 1990- 26 August 2018 (has links)
Orientador: Edvaldo Sabadini / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-26T20:28:41Z (GMT). No. of bitstreams: 1 Clinckspoor_KarlJan_M.pdf: 16885506 bytes, checksum: bf5bdbaa99957493be29510c93bbd89d (MD5) Previous issue date: 2015 / Resumo: O papel estrutural de cossolutos derivados de cinamato para a formação de micelas gigantes de surfactantes catiônicos. Micelas gigantes (MG) são estruturas de autoassociação de surfactantes que podem ser formadas pela adição de cossolutos aromáticos, como salicilato, a soluções de surfactantes catiônicos como CTAB e TTAB (brometo de cetiltrimetilamônio e brometo de tetradeciltrimetilamônio). Estudou-se o papel de derivados estruturais do ácido cinâmico (C6H6-CH=CH-COOH), a saber, ácido ortohidroxicinâmico (OHCA), ácido ortometoxicinâmico (OMCA), ácido ortohidroxifenilpropiônico (OHPA), ácido 3-fenilpropiônico (3PPA) na formação de MG de CTAB e TTAB, em pH 6, e também foi estudada a variação de pH de soluções com OHCA, entre pH 6 e 11. As técnicas principais utilizadas foram: Reologia oscilatória, Espalhamento estático de luz (SLS), Calorimetria de titulação isotérmica (ITC), Espalhamento de raio X em baixo ângulo (SAXS) e Microscopia de transmissão eletrônica em temperaturas criogênicas (Cryo-TEM). Variando a estrutura dos cossolutos, foi possível observar que tanto a presença da ligação dupla do cinamato quanto a de uma hidroxila na posição orto contribuem para a formação de MGs. Quando o cossoluto possui esses dois grupos, que é o caso do OHCA, as micelas são formadas em proporções muito baixas de [TTAB]/[Cossoluto], como foi visto por ITC. Quando o cossoluto possui somente um dos grupos, a formação de micelas ocorre em proporções maiores (OHPA, OMCA, Cinamato) e quando possui nenhum dos dois grupos (3PPA), não são formadas micelas gigantes. As estruturas das micelas de cada região do ITC foram inferidas por SLS e ensaios viscosimétricos. Variando-se o pH das soluções de OHCA com TTAB, observou-se que quanto maior o pH, as micelas são formadas em proporções maiores e a entalpia de formação é menor. Por reologia, foi visto que em pH 9, o sistema formado possui um tempo de relaxação muito maior que em pHs 6-8, em pH 10 o sistema não é mais Maxwelliano e em pH 11, a solução é fluída como água. Isso ocorre porque, quanto maior o pH, o OHCA se torna mais hidrofólico e menor é sua partição no interior da micela / Abstract: The structural role of cossolutes derived from cinnamate in the formation of cationic surfactante wormlike micelles. Wormlike micelles (WLM) are surfactant self-assembly structures that can be formed by the addition of aromatic cossolutes, like salicylate, to solutions of cationic surfactants like CTAB and TTAB (cetyltrimethylammonium bromide and tetradecyltrimethylammonium bromide). We studied the structural role of structural derivatives of cinnamic acid (C6H6-CH=CH-COOH), namely, orthohydroxycinnamic acid (OHCA), orthomethoxycinnamic acid (OMCA), orthohydroxyphenylproprionic acid (OHPA), 3-phenylpropionic acid (3PPA) on the formation of wormlike micelles of CTAB and TTAB, at pH 6. We also studied the variation of pH, ranging from 6 to 11, on OHCA WLM. The main techniques used were: Oscillatory rheology, static light scattering (SLS), isothermal titration calorimetry (ITC), small angle x-ray scattering (SAXS) and cryogenic temperature transmission electron microscopy (Cryo-TEM). By varying the structure of the cossolutes, it was possible to see that both the presence of a double bond and an ortho-hydroxyl favor the formation of WLM. When the cossolute has both groups (OHCA), the WLM are formed at very low [TTAB]/[Cossolute], as was seen by ITC. When the cossolute has only one of those groups the WLMs are formed at higher proportions (OHPA, OMCA, Cinnamate) and when it doesn't have either groups (3PPA), no WLMs are formed. The structures at each concentration region were inferred by viscosimetry and SLS. When varying the pH of OHCA, it was observed that the higher the pH, the proportion for the formation of WLM is increased, and the enthalpy of formation is smaller. By rheology it was seen that at pH 9, the system formed has a much higher relaxation time than at pH 6-8, at pH 10 the system isn't Maxwellian and at pH 11, the system is liquid. This occurs because by increasing the pH, the hydrophilicity of OHCA is increased, and smaller is its partition on the WLM palisade / Mestrado / Físico-Química / Mestre em Química
293

Ligação e troca iônica em interfaces zwitteriônicas / Ion Binding and Exchange in zwitterionic interfaces

Mauricio da Silva Baptista 10 July 1992 (has links)
Investigou-se o efeito do \"caráter iônico\" de interfaces zwitteriônicas, formalmente neutras, representadas por micelas e vesículas obtidas de monômeros com cabeça hidrofílica dipolar, nas propriedades de acumulação e troca de espécies iônicas. Os sistemas estudados incluíram, micelas de 1-(N-hexadecil-N,N-dimetilamônio) propanossulfonato (HPS), Hexadecil fosforil colina (C16PN), 3-hexadecil glicerofostidil colina (lisoPC) e vesículas de fosfatidil colina (PC). O estudo da ligação e troca iônica nestas interfaces foi monitorado a partir de efeitos sobre reações prototrópicas de sondas como a 8-hidroxi-1,3,6-pirenotrisulfonato de sódio (piranina). Observou-se a ligação crescente da piranina na seguinte ordem lisoPC < C16PN < HPS e troca iônica com sais adicionados (função do ânion) na ordem inversa, isto é, lisoPC &gt; C16PN &gt; HPS. Estudos de reprotonação de 1 e 2 naftóis incluídos nestes agregados, via salto de pH induzido por laser, revelaram um perfil de concentração de prótons inverso àquele das cargas do dipolo, isto é, concentração nos polos negativos e exclusão nos positivos. Este resultados foram ainda reforçados por estudos de excitação de volume, via espalhamento de luz, com micelas de HPS em função de sal adicionado. A partir destes resultados propôs-se um modelo de capacitor esférico imerso em meio eletrolítico para estas interfaces, o qual se mostrou bastante versátil na análise e previsão de resultados experimentais. Em suma, estabeleceu-se no presente trabalho a visão de que interfaces dipolares são geradoras de assimetria iônica na circunvizinhança da interface, assimetria esta de polaridade invertida àquela do dipolo radialmente disposto à interface. A generalidade deste modelo pode ser extrapolado para outras interfaces e colaborar na compreensão de diversos processos que dependem da acumulação e troca iônica. / The effect of ionic domains of formally neutral zwitterionic interfaces, represented by micelles and vesicles obtained with dipolar headgroups amphiphiles, on the binding and exchange of ionic species were investigated. The systems studied included: aqueous micelles of 1-(N-hexadecyl-N,N-dimethylammonio) Propane Sulfonate (HPS), Hexadecyl Phosphoryl Choline (C16PN), and 1-hexadecylglycerophostidyl Choline (lisoPC) and vesicles of Phosphatidylcholine (PC). Binding and ion-exchange processes were assessed from the effect of these agreggates on prototropic reactions of probes such as 8-hydroxy-1,3,6-pyrenetrisulfonate pyranine). Binding of pyranine increased in the following order lisoPC < C16PN < HPS. The effectiveness of anion dependent salt displacement of the probe from the aggregates was opposite to that of affinities, i.e. lisoPC &gt; C16PN &gt; HPS. Laser pH jump studies with 1 and 2 naphtols incorporated in these aggregates revealed a proton concentration profile inverse to that of the charged dipole, that is, accumulation in the region vicinal to the negatively charged group and exclusion from the positive end of the dipole. This finding were substantiated by HPS micelle excluded volume data, obtained from light scattering studies as function of added salt. A model of a spherical capacitor immersed in an electrolyte media for these interfaces was proposed. This model accounts for satisfactorily the observed characteristics of these interfaces. The model establishes that dipolar interfaces generate ionic asymmetries in the neighborhood of the interface that opposes the radially extended monomer dipole. The generality of the model can be very helpful in the analysis and understanding of several processes occurring in/at zwitterionic interfaces.
294

Rezonanční přenos energie v prostředí hydrogelové matrice / Resonance energy transfer in the environment of the hydrogel matrix

Janča, David January 2017 (has links)
The diploma thesis deals with resonance energy transfer in hydrogel matrix enviroment. In the theoretical part, all the important features of these systems and their components are summarized and all the principles for explaining the method used are described. The work also includes a short literary background research. In the experimental part, the resonance energy transfer was measured in micellar solutions and hydrogels in 0.15 M NaCl medium. The hydrogels were formed on the basis of interaction of the surfactant with the oppositely charged polyelectrolyte. As a positively charged surfactant, carbethopendecinium bromide (Septonex) was chosen and hyaluronan as the negatively charged polyelectrolyte. Perylene with fluorescein and perylene were selected as fluorescent pairs for RET. It has been found that increasing concentration of the acceptor molecule increases the intensity of RET, in other word the rate of acceptor binding to the donor. In the study of fluorescent pair of perylene with DiO was observed, that it was not appropriate to use fluorescence probe DiO at higher concentrations. Experiments were carried out to determine whether RET changes in the time from the point of mixing the donor and acceptor fluorescence probes together. This phenomenon has not been confirmed. In hydrogels, the effect of increasing surfactant concentration and molecular weight of hyaluronan was observed. The resulting analysis showed that the molecular weight of hyaluronan has a significant effect on RET efficiency in hydrogels.
295

Fizičko-hemijske karakteristike mešovitih micela soli žučnih kiselina i nejonskih surfaktanata / Physico-chemical properties of mixed micelles of salts of bile acids and nonionic surfactants

Ćirin Dejan 14 May 2015 (has links)
<p>Surfaktanti imaju značajnu primenu u farmaciji i medicini. Ove supstance se primenjuju u farmakoterapiji, koriste se za solubilizaciju hidrofobnih lekova, a pojedina ispitivanja pokazuju da mogu unaprediti bioraspoloživost određenih aktivnih supstanci. U poslednje vreme se sve vi&scaron;e pažnje posvećuje ispitivanju sme&scaron;a surfaktanata, po&scaron;to je utvrđeno da sistemi dva ili vi&scaron;e surfaktanta često pokazuju poželjnija svojstva od pojedinačnih surfaktanata za aplikaciju u farmaciji i medicini. U ovoj disertaciji su ispitivani binarni sistemi osam anjona žučnih kiselina i dva nejonska surfaktanta (polisorbat 40 i polisorbat 80). Ciljevi su određivanje vrednosti kritičnih micelarnih koncentracija ispitivanih sme&scaron;a surfaktanta, utvrđivanje međudejstva između različitih surfaktanta u njihovim me&scaron;ovitim micelama, kao i ispitivanje uticaja stukture ispitivanih surfaktanata na fizičko-hemijske karakteristike me&scaron;ovitih micela. Rezultati pokazuju da ispitivane sme&scaron;e imaju znatno niže vrednosti kritičnih micelarnih koncentracija od anjona žučnih kiselina. Sme&scaron;e anjona žučnih kiselina i polisorbata 40 imaju manje vrednosti eksperimentalnih kritičnih micelarnih koncentracija, od izračunatih, idealnih, vrednosti, &scaron;to ukazuje na postojanje sinergističkih interakcija u me&scaron;ovitim micelama. Sme&scaron;e anjona žučnih kiselina i polisorbata 80 imaju uglavnom veće vrednosti kritičnih micelarnih koncentracija od idealnih vrednosti, &scaron;to može biti posledica postojanja antagonističkih interakcija između gradivnih jedinica me&scaron;ovitih micela. Vrednosti interakcija, koje dovode do neidealnog pona&scaron;anja sistema surfaktanata, su određene računanjem vrednosti interakcionog parametra, &beta;<sub>1,2</sub>, prema regular solution theory. Sistemi anjona žučnih kiselina i polisorbata 40 imaju negativne vrednosti interakcionog parametra, dok sistemi anjona žučnih kiselina i polisorbata 80 imaju uglavnom pozitivne vrednosti interakcionog parametra. Poređenjem fizičko-hemijskih parametara me&scaron;ovitih micela je utvrđeno da postojanje privlačnih međudejstava između hidrofilnih delova različitih surfaktanata najverovatnije potiče od vodoničnih veza koje se formiraju između hidrofilnih grupa anjona žučnih kiselina i polioksietilenskih delova. Pozitivne vrednosti &beta;<sub>1,2</sub> parametra su najverovatnije posledica sterno krute cis dvostruke veze oleinske kiseline u molekulu polisorbata 80, usled čega se lipofilni deo ovog nejonskog surfaktanta teže pakuje u jezgru me&scaron;ovitih micela. Pretpostavlja se da zbog toga dolazi do formiranja dimera anjona žučnih kiselina u me&scaron;ovitim micelama u kojima se javljaju odbojne interakcije između negativno naelektrisanih karboksilatnih grupa.</p> / <p>Surfactants have important application in pharmacy and medicine. These substances are applied in pharmacotherapy, they are used for hydrophobic drug solubilisation, and certain investigations indicate they can improve bioavailability of certain active substances. Lately, investigations of surfactant mixtures have gained a lot of attention, since it was found that systems of two or more surfactants often show more desirable properties than the individual surfactants, for application in pharmacy and medicine. In this dissertation, binary systems of eight bile acid anions and two nonionic surfactants (polysorbate 40 and polysorbate 80) were investigated. The aims were to determine values of critical micelle concentrations of investigated surfactant mixtures, interactions between different surfactants in their mixed micelles, and to investigate the influence of the structure of investigated surfactants on physico-chemical characteristics of mixed micelles. The results indicate that investigated mixtures have significantly lower values of critical micelle concentrations than bile acid anions. Mixtures of bile acid anions and polysorbate 40 have&nbsp; lower values of experimentally obtained critical micelle concentrations than the calculated, ideal, values, indicating the existence of synergistic interactions in mixed micelles. Mixtures of bile acid anions and polysorbate 80 have mainly higher values of critical micelle concentrations than the ideal values, what could be due to the existence of antagonistic interactions between building units of mixed micelles. The values of the interactions, attributing to the nonideal behaviour of the surfactant systems were obtained by calculating the values of the interaction parameter, &beta;1,2 , according to the regular solution theory. Systems of bile acid anions and polysorbate 40 have negative values of the interaction parameter, while systems of bile acid anions and polysorbate 80 have mainly positive values of interaction parameter. By comparing the physico-chemical parameters of mixed micelles, it was determined that existence of attractive interactions between hydrophilic parts of different surfactants most probably originates from the hydrogen bonds, which are formed between hydrophilic groups of bile acid anions and polyoxyethylene parts. Positive values of &beta;1,2 parameter are most probably due to sterically rigid cis double bond of oleic acid in polysorbate 80 molecule, causing the lipophilic tail of this nonionic surfactant to pack less easily in the core of mixed micelles. It is hypothesised that this influences formation of dimers of bile acid anions in mixed micelles, where repulsive interactions emerge between negatively charged carboxylate groups.</p>
296

Uticaj dužine hidrofobnog segmenta homolognih polisorbata na termodinamičke parametre binarnih mešovitih micela polisorbata i Tritona X-100 / Influence of hydrophobic segment length of homologues polysorbates on thermodynamic parameters of binary mixed micelles of polysorbates and Triton X-100

Vapa Ivana 29 September 2016 (has links)
<p>Binarne me&scaron;ovite micele su značajne u farmaceutsko-farmakolo&scaron;kim primenama, u kojima lek kao povr&scaron;inska aktivna supstanca može da bude gradivna jedinica binarne micelle (promena bioraspoloživosti, mehanizam resorpcije itd.). Takođe su važne i me&scaron;ovite micele kod kojih su gradivne jedinice biosurfaktanti (biokompatibilni solubilizatori lekova). U kozmetičkoj, prehrambenoj i industriji detergenata me&scaron;ovite micele su uveliko zastupljene. Važno je nalaženje binarnih sistema surfaktanata koji u me&scaron;ovitim micelama poseduju sinergističko međudelovanje (negativna vrednost interakcionog parametra). Takva binarna sme&scaron;a surfaktanata ima nižu vrednost kritične micelarne koncentracije od hidrofobnije komponente sme&scaron;e. U prvom delu rada je ispitivan uticaj dužine hidrofobnog segmenta homolognih Tween-ova iz me&scaron;ovitih micela sa Triton-om X100 na interakcioni parametra ( i, j &beta; ) i dodatnu Gibbs-ovu energiju (GE ), takođe ispitivao se i uticaj temperature na stabilnost proučavanih me&scaron;ovitih micela (273,15-328,115 K). Kritične micelarne koncentracije čistih surfaktanata i njihovih binarnih sme&scaron;a su određeni spektrofluorometrijski uz primenu pirena kao probnog molekula. Nađeno je da na svakoj ispitivanoj temperaturi povećanje dužine zasićenog alifatičnog niza polisorbata povećava stabilnost me&scaron;ovite micele ( , 0 i j &beta; &lt; i GE &lt; 0 ) u odnosu na idealnu me&scaron;ovitu micelu. Prisustvo C9 dvostruke veze u ostatku oleinske kiseline Tween-a 80 umanjuje sinergistički efekat ovog polisorbata u odnosu na Tween 60, koji ima hidrofobni segment sa istim brojem C atoma, ali bez olefinske veze. Dodatna slobodna entalpija ispod temperature 298.15 K određena je entropijskim doprinosem, a iznad 298.15 K entalpijskim doprinosom. U drugom delu rada ispitivane su binarne sme&scaron;e surfaktanata Tween 85/Triton X100 i Tween 85/Triton X165 u vodenom rastvoru u intervalu temperature od 273.15 K do 323.15 K. Pri temperaturama od 273.15 K i 283.15 K između različitih gradivnih jedinica binarnih me&scaron;ovitih micela postoje sinergističke interakcije na čiju veličinu ne utiče razlika u dužini polioksietlienskih nizova Triton-a X100 i Triton-a X165. Na većim vrednostima temperature duži polioksietilenski niz Triton-a X165 pokazuje stabilizirajuči efekat u me&scaron;ovitoj miceli sa Tween-om 85 u odnosu na me&scaron;ovite micele Tween 85/Triton X100. Kod ispitivanih binarnim me&scaron;ovitim micela ne može se prihvatiti aproksimacija regularnih sme&scaron;a o nula vrednosti dodatne entropije formiranja binarne me&scaron;ovite micele.</p> / <p>Binary micelles are important in pharmaceutical-pharmacological applications, in which drug as surface active substance can be building unit of binary micelle (influencing bioavailability change, change of resorption mechanism etc.). Mixed micelles in which building units are biosurfactants (biocompatible drug solubilizers) are also important. In cosmetics, food and detergent industry mixed micelles are widely present. It is important to find binary surfactant systems having synergistic interactions (negative value of interaction parameter). That binary surfactant mixture has lower critical micelle concentration value than more hydrophobic component of the mixture. In the first parth of this work, influence of hydrophobic segment length of homologues Tweens in mixed micelles with Triton X-100 on the interaction parameter value ( i, j &beta; ) and an excess Gibbs energy (GE ) was investigated. Also, influence of temperature on the stability of investigated mixed micelles has been investigated (273.15-328.15 K). Critical micelle concentration values of pure surfactants and their binary mixtures were determined spectrofluorimetrically using pyrene as a probe molecule. It was found for every investigated temperature that increase in length of saturated aliphatic side chain of a polisorbate increases the stability of investigated mixed micelles (&beta; &lt; and GE &lt; 0 ) compared to ideal mixed micelles. Presence of the C9 double bond in oleic acid residue of Tween 80 reduces synergistic effect of this polysorbate compared to Tween 60 which contains hydrophobic segment with the same number of C atoms but without olefin bond. Excess free enthalpy below the 298.15 K is determined with entropic contribution, but above 298.15 K with enthalpic contribution. In the second parth of this work, binary surfactant mixtures of Tween 85/Triton X100 and Tween 85/Triton X165 have been investigated in water solution in the temperature range from 273.15 K to 323.15 K. At the temperatures of 273.15 K and 283.15 K between different building units of binary mixed micelles synergistic interactions exist, which size is not affected by difference in length of the polyoxyethylene chains. At higher temperatures, longer polyoxyethylene chain of Triton X165 shows more stabilizing effect in mixed micelle with Tween 85 than in mixed micelles of Tween 85/Triton X100. For investigated binary mixed micelles, regular solution theory approximation about zero value of excess entropy of binary mixed micelle formation cannot be accepted.</p>
297

Kationické povrchově aktivní látky a hodnocení jejich vlastností / Cationic surface active compounds and evaluation of its properties

Pekařová, Kateřina January 2018 (has links)
Charles University Faculty of Pharmacy in Hradec Králové Department of Biophysics and Physical Chemistry Consultant: PharmDr. Jan Marek, Ph.D. Supervisor: doc. PharmDr. Veronika Nováková, Ph.D. Student: Kateřina Pekařová Title of Thesis: Cationic surface active compounds and evaluation of its properties Quaternary ammonium salts are used as surfactants in many branches of the food, pharmaceutical and chemical industries. The basic properties of these substances were studied in the thesis. The critical micellar concentration of the homologous series of five substances was determined using the conductometric method. The theory of declining critical micellar concentration with the increasing length of the side alkyl chain has been verified. The hydrolytic activity of two commonly used cationic surfactants benzalconium chloride and benzoxonium chloride for the decomposition of the organophosphorus pesticide fenitrothion was tested. For these two substances, the effect of pH and temperature changes was evaluated. The influence of tenside concentration was also monitored. Benzoxonium chloride at 50 řC and pH 11was found as the most effective hydrolytic catalyst for the decomposition of the organophosphorus pesticide fenitrothione.
298

Nanočástice citlivé na vnější podněty obsahující fenylboronové spojky jako potenciální nosiče léčiv / Stimuli - responsive nanoparticles with boronic ester linkages as a potential carrier for drug delivery

Hlavatovičová, Eva January 2020 (has links)
This thesis deals with the post-polymerization functionalization of a pH-responsive poly(styrene)-b-poly(4-vinyl pyridine)-b-poly(ethylene oxide) triblock terpolymer with stimuli responsive and diol-binding 2-bromomethyl-4-fluorophenylboronic acid and 2- bromomethyl-phenylboronic acid suitable for biomedical applications. A reproducible method of quaternization of poly(4-vinyl pyridine) block with prescriptible quaternization ratio was developed and the reaction yield was analyzed by 11 B, 1 H NMR and infrared spectroscopy. A reproducible self-assembly protocol for stable nanoparticles from functionalized stimuli-responsive triblock terpolymer was found, and the nanoparticles were studied by static, dynamic and electrophoretic light scattering, and cryogenic transmission electron microscopy. Fluorescence and UV-VIS spectroscopy measurements were performed for description of boron-ester linkages formation and hydrolysis with model drug Alizarin as a study of encapsulation and release reactions together with sugar sensing reactions for potential drug delivery.
299

Towards Lignin Valorisation: Development of Vanadium-based Catalytic Systems for C-C Oxidative Cleavage in H2O

Denis, William 28 September 2020 (has links) (PDF)
Every year millions of tons of lignin, a complex biopolymer present in plants that naturally contains aromatic subunits, are produced as a by-product of industries like the food sector and paper sector. Until now it has been considered as a waste but proper valorisation through optimized depolymerization techniques would allow to recover of high-added value fine chemicals and bulk commodities. Vanadium(V) triphenolamine complexes (VO-TPA), developed and studied in the group of Giulia Licini (University of Padova, IT), are of interest in this context as they are efficient catalysts for the oxidative cleavage of carbon-carbon bonds typical of those present in lignin. However, the mechanism of this reaction had not yet been elucidated and the catalysts have exclusively been used in organic solvents. This Thesis is a contribution to the further development of these catalysts and takes different Green Chemistry principles into account such as waste prevention, atom economy, renewable feedstocks, catalysis, energetic efficiency and the use of benign solvents. A first part of this thesis is a contribution to the elucidation of the reaction mechanism. The work was undertaken with vicinal diols, which are the simplest model compounds of lignin. Based on a review of the literature, radical trapping experiments, kinetics, 13C KIE experiments, Hammett plots and multi-parametric correlations, the C-C cleavage of a non-oxo or oxo chelate has been identified as the rate determining step. Attempts were made to synthesise the chelate and identify it via MS. Moreover, three hypothetic pathways were posited to reach this intermediate. Isotopic labelling experiments, determination of reaction activation parameters via an Eyring plot and computations of the different pathways along EPR elucidation of reduced species, have been used to discriminate the operative mechanism. The second part of this thesis is devoted to the transfer of the reaction into water, which can be considered a benign solvent. The VO-TPA complexes were successfully transferred to water using both non-ionic TPGS-750-M and zwitterionic DPC micelles. The latter maintained the catalyst stability over a broad pH range and temperature range which was not the case with the non-ionic micelles. The substrate scope was evaluated with the DPC micelles and a strong selectivity was observed for hydrophobic substrates. After scaling up the process to reach standards used in the literature, mixed DPC/TPGS micelles were characterized and used as a simple solution to combine the pH stability of the former and extractive properties of the latter. This allowed to completely recycle the micellar phase while maintaining good yields. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished
300

Coumarin-based molecular probes : exploring the spectroscopic properties of complex mixtures and applications in colloid chemistry

Zhao, Shangqing January 2018 (has links)
Warfarin is a well-known anticoagulant drug that is used to prevent cardiovascular disease and blood coagulation such as thrombosis. In this study, the main aim was to investigate the photo physical characteristics of warfarin in the different molecular environments provided by sodium dodecyl sulfate (SDS) micelles by using ultraviolet absorption and fluorescence emission spectroscopic techniques. Warfarin and a structural analogue not existing in solution as a cyclic hemiketal, phenprocoumon, were mixed with different concentrations of SDS and spectral changes for these warfarin and phenprocoumon were recorded. Interestingly, results demonstrated, based on an evident increase in the absorption intensity at 273 nm and an evident blue shift in the fluorescence emission spectrum after the addition of an increasing concentration of SDS, that primarily the cyclic hemiketal isomer of warfarin was found to be solvated by SDS micelles at an apparent recorded critical micelle concentration of ~8mM.  Altogether these observations suggest that warfarin may be used as a molecular probe to explore the polarities of complex colloidal mixtures. Moreover, the possibility of using micelles for controlling the isomeric state of warfarin is interesting and can potentially be used for better controlling dosage of warfarin thereby reducing side effects.

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