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1
Rubió, Piqué Laura. "Phenol-enriched olive oil with its own phenolic compounds and complemented with phenols from thyme: a functional food development model." Doctoral thesis, Universitat de Lleida, 2014. http://hdl.handle.net/10803/146133.
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L'enriquiment de l’oli d'oliva amb els seus propis fenols esdevé una estratègia interessant per augmentar i normalitzar la ingesta diària d’hidroxitirosol sense augmentar el consum calòric. No obstant això, olis amb alt contingut fenòlic proporcionen un gust amarg que podria provocar rebuig entre els consumidors. A més, altes dosis d'hidroxitirosol podria tenir una acció pro-oxidant. En aquesta tesi es va plantejar l'estratègia d'enriquiment d’un oli d'oliva no només amb els seus propis fenols, sinó amb fenols complementaris d'herbes aromàtiques, concretament de farigola, amb la hipòtesi de que apart de proporcionar millores en l'estabilitat de l'oli i l'acceptació dels consumidors, també podria aportar beneficis addicionals per a la salut. Un cop desenvolupat l'oli d'oliva enriquit en fenols, es va avaluar la biodisponibilitat dels fenols mitjançant mètodes in vitro i in vivo, avaluant possibles interaccions o sinergies entre ambdues fonts fenòliques.El enriquecimiento de aceite de oliva con sus propios fenoles se convierte en una estrategia interesante para aumentar y normalizar la ingesta diaria de hidroxitirosol sin aumentar el consumo calórico. Sin embargo, aceites con alto contenido fenólico tienen un sabor amargo que podría provocar rechazo entre los consumidores, y además sus altas dosis de hidroxitirosol podría tener una acción pro-oxidante. En esta tesis se planteó la estrategia de enriquecimiento de aceite de oliva no sólo con sus propios fenoles, sino con fenoles complementarios de hierbas aromáticas, concretamente tomillo, con la hipótesis de que no sólo podría proporcionar mejoras en la estabilidad del aceite y la aceptación de los consumidores, sino que podría aportar beneficios adicionales para la salud. Una vez desarrollado el aceite de oliva enriquecido se evaluó la biodisponibilidad de los fenoles mediante métodos in vitro e in vivo, evaluando posibles interacciones o sinergias entre ambas fuentes fenólicas.
The enrichment of olive oil with its own phenolic compounds becomes an interesting strategy to increase and standardize the daily intake of hydroxytyrosol without increasing the caloric intake. Concerning olive oils with high phenolic content, however, they have a bitter taste, which could promote a refusal among consumers, and contain high doses of hydroxytyrosol that could have a pro-oxidant action. In this context, the strategy of enriching olive oil not only with its own phenolics but also with complementary phenols from aromatic herbs was outlined in this thesis with the hypothesis that it could not only improve olive oil stability and consumers’ acceptation but also provide additional health benefits. In this thesis a phenol-enriched olive oil was developed using the aromatic herb of thyme, and the bioavailability of the phenolic compounds was assessed, evaluating possible interactions or synergies between both sources through in vitro and in vivo approaches.
2
Lucach, Sandra Ortega. "Phenols in petroleum systems." Thesis, University of Newcastle Upon Tyne, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273711.
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Goss, Ben. "Novel phenolic composites." Thesis, Queensland University of Technology, 1997. https://eprints.qut.edu.au/36933/1/36933_Goss_1997.pdf.
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Composites were prepared from a phenolic resin formulation reinforced with ultra high modulus polyethylene (UHMPE) fibre. Two commercially prepared samples of UHMPE were used: Spectra® prepared by Allied Signal in the USA and Dyneema® prepared by DSM in Holland. To these fibres a number of surface treatments were applied, predominantly oxygen and water plasma, in order to improve composite properties.
The effect of treatment was monitored usmg X-ray Photoelectron Spectroscopy (XPS), and treatment time was optimised by this technique. The influence of treatment time on fibre tensile strength was also determined. The change in adhesion was determined using the fibre pullout test and other composite properties were determined by interlaminar shear strength (ILSS) and flexural tests. An improvement in adhesion was observed. The effect of fibre volume fraction on ILSS and shear modulus was also determined.
It was found that the oxygen / carbon ratio reached a threshold after 60 seconds whereas adhesion was maximised after only 20 to 30 seconds. SEM examination showed that this was due to the occurrence of a second failure mechanism, shear failure of the fibre, that occurred when interfacial adhesion exceeded fibre shear strength. This was also observed in the ILSS tests. The measurement of ILSS was used to optimize both the surface treatment and volume fraction of fibre in the composite. It is the onset of fibre shear failure that is the limiting factor in UHMPE composite materials.
4
Fimbres, Michael. "Competitive sulfonimidate alkylations of phenols." Thesis, California State University, Long Beach, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1526904.
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Ethyl N-tert-butyl-4-nitrobenzenesulfonimidate and isopropyl N-(1-adamantyl)-4-nitrobenzenesulfonimidate have been shown to alkylate a variety of different phenols, along with thiophenol and selenophenol. It was shown that ethylation and isopropylation can be successfully carried out using these sulfonimidates with the help of an acid catalyst, tetrafluoroboric acid dimethyl ether complex. Their ability to alkylate selectively on functionally similar groups resulted in the formation of ethers, sulfides, and selenides. Competitive reactions with sterically hindered phenols formed the less sterically hindered ethers in greater amounts. Electronic substituent effects in para-substituted phenols favored alkylation on the more electron rich phenols. Hammett sigma para-substituent constants correlated with relative rates of phenol alkylations to give negative reaction constant (p) values for each alkyl sulfonimidate reagent. Thus, the major goal of this project was accomplished in finding general trends in functional groups, steric hindrance, and substituent effects to make reasonable predictions for sulfonimidate reactions in the future.
5
Johns, Stephen Christopher. "De Novo Synthesis of Phenols." Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/4646.
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This thesis is divided into three chapters. In the first, the methods currently available for the synthesis ofphenols from acyclic precursors are reviewed. The review concentrates on methods that have been usedto form a range of phenols and is divided up according to the type of chemistry employed. The secondchapter describes the development of a novel route to phenols. Initial optimisation results are describedfirst, followed by the synthesis of a library of phenols. The majority of these have not been reportedpreviously. The attempted extension of this work to the formation of anilines, nitrobenzenes and morehighly oxygenated aromatics is also presented. Finally, work towards the synthesis of the aglycone ofpseudopterosin A is described, following a route that would utilise the phenol-forming chemistry in amore complex natural product environment. The final section details the experimental procedures usedto form the compounds described in section two, along with associated spectroscopic data.
6
Balasainath, Ravindra Kotha. "Regiospecific Synthesis of Ortho Substituted Phenols." TopSCHOLAR®, 2011. http://digitalcommons.wku.edu/theses/1084.
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Phenol is highly reactive toward electrophilic aromatic substitution. By this general approach, many groups can be appended to the ring, via halogenation, acylation, sulfonation, and other processes. Phenol contains the hydroxyl group (–OH), which is a strongly activating ortho/para directing group in aromatic electrophilic substitution (AES). AES gives a mixture of ortho-and para isomers, which must be separated.
The strong directing ability of phenol can also result in multiple substitutions on the aromatic ring which could be a major concern in the regiospecific synthesis of phenols. AES and Directed ortho--Metalation (DoM) are the only ways to directly substitute a proton on an aromatic ring and to synthesize regiospecifically substituted phenols. Phenol is a versatile precursor to a large collection of drugs, most notably aspirin, but also many herbicides and pharmaceuticals. AES reactions are useful in regiospecific synthesis as a way of introducing many reactive groups on the benzene ring and also help us to design a suitable method for synthesizing compounds in an efficient manner.
Dimethylbenzylamine products are obtained as a result of the reaction of phenols with Eschenmoser’s salt (N,N-Dimethylmethyleneiminium iodide). This approach enables us to prepare regiospecifically ortho substituted phenols by using the AES protocol. We have discovered that Eschenmoser’s salt has the ability in basic medium containing triethylamine (TEA) to remove the proton and bond to the aromatic ring exclusively in ortho position to the –OH substituent.
Our research work focused on efforts to render isolated products with minimum impurities, greener and more atom economical by use of limiting reagent in the reactions. For the purpose of evaluation of the obtained compounds and intermediates we use Gas Chromatography (GC), Gas Chromatography coupled with Mass Spectrometry (GC-MS) and Nuclear Magnetic Resonance (NMR).
Our future work is to synthesize novel benzoheterocyclic compounds from the ortho-derivatised phenols as well as multi-substituted aromatic compounds. The dimethylamino methyl group can act as a directing group in the ortho-lithiation process; subsequent ortho--metalation and treatment with electrophiles generates 1,2,3- trisubstituted phenolic derivatives. Thus, phenolic precursors can be transformed into numerous derivatives which can be used in the chemical, agricultural and pharmaceutical industries.
7
Izimas, M. "Selective control of chlorination of phenols." Thesis, Swansea University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637380.
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The chlorination of meta-cresol by sulfuryl chloride in the presence of different sulfur containing catalysts was studied. In homogeneous conditions, the chlorination of meta-cresol was catalysed by dialkyl sulfides and dithia-alkenes. The influence of various reaction parameters was investigated. The dithia-alkanes were not commercially available and needed to be synthesised prior to their use. A new method for the synthesis of unsymmetrical dithia-alkanes was developed. The chlorination of meta-cresol using di-iso-propyl sulfide and di-n-butyl sulfide was scaled up and the reaction mixture separated by fractional distillation. The catalyst was recovered and reused. 5,18-Dithiadocosane, a successful catalyst for the chlorination of meta-cresol, was also tested as catalyst for the chlorination of phenol, anisole, meta-xylenol, toluene and naphthalene. In heterogeneous conditions, the chlorination of meta-cresol was catalysed by polymers containing thia-alkyl groups. The synthesis of the polymers by modification of bromopolystyrene and Merrifield resin was studied and a new method was developed to avoid crosslinking. A polythia-alkane was also synthesised from 1,6-hexanedithiol and 1,8-dibromo-octane.
8
Amiri, Fariba. "Influence of pH and NOM on Sorption of Phenols onto Aquifer Material." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2005. http://nbn-resolving.de/urn:nbn:de:swb:14-1112166354807-33548.
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Geosorption processes play an important role as retardation mechanism in subsurface transport of organic water constituents. Geosorption behaviour of Ionisable Hydrophobic Organic compounds (IHOCs) especially influence of dissolved natural organic materials on their sorption coefficients is poorly investigated. In this study influence of pH and NOM on the sorption of three different phenols (2-methyl-4,6-dinitrophenol, 2,4,6-trichlorophenol and pentachlorophenol) on a natural sandy aquifer material collected from a bank filtration site was studied in flow through column experiments. In first step the sorption coefficients of investigated phenols from NOM-free solutions with different pH values were determined. Single as well as multi (mixed) solutes experiments confirmed that there was no competition effect among the phenols investigated. An increasing sorption/retardation was observed with decreasing pH. A linear model was used to resolve the apparent sorption coefficient into an ionised species and neutral species component. This model allows a prediction of apparent sorption coefficients for any pH value. Analysis of data also revealed that the anion of 2-M-4,6-DNP show no significant sorption and a simple model based on the neutral form sorption coefficient was useful in predicting the apparent sorption coefficient over the entire pH range investigated. For 2,4,6-TCP and PCP, the anion sorption is much lower than that of the neutral species but cannot be neglected completely. For PCP, the anion sorption is even as high as the sorption of neutral 2,4,6-TCP. Thus for such hydrophobic phenols prediction of sorption based only on the partitioning of non-dissociated species may lead to an error, especially at high pH values (> pKa), where ionised form is present predominantly. On the other hand prediction of sorption based on the partitioning of non-dissociated species is useful at pH < pKa or in cases where the anion sorption can be neglected. The advantage of this prediction is that it allows predicting the pH-dependent sorption only on the basis of LFER correlations. It was shown that the organic carbon normalized sorption coefficients of the neutral forms of the phenols can be predicted better by solubility based regression correlations than by n-octanol-water partition coefficient based correlations. In second step the apparent sorption coefficients of investigated phenols from NOM-containing solutions (mixed solution of phenols dissolved in natural river water) with different pH values were determined; the sorption coefficients obtained from this step were compared with the results of the first step examinations. Analysis of data revealed that binding of 2-M-4,6-DNP by dissolved humic substances (DHS) reduces the sorption coefficient significantly. In contrast to it, the sorption of the more hydrophobic chlorinated phenols was not affected by DHS. A strong reduction of sorption onto aquifer material caused by complex formation with DHS was also observed for a second nitrophenol (2,4-DNP) and seems to be typically for nitrophenols. A combined sorption and complex formation model was proposed which could be used successfully to describe the effect of pH and NOM concentration on sorption reduction and to estimate binding constants. The binding constant found for 2-M-4,6-DNP is much higher than those reported by Ohlenbusch and Frimmel, 2001, for chlorophenols associated with Aldrich humic acid. This can be interpreted as a result of specific interactions between the nitrophenol and DHS. This phenomenon may cause an increase of the amount of nitrophenols, which can be transported with the groundwater flow and has to be considered in transport modelling, especially in cases where pH is lower than pKa. The models developed here are a useful tool to describe the influence of pH and NOM on geosorption processes and to estimate the Kd values which have to be used in transport models.
9
Bassey, E. N. "The extraction of phenols from ammoniacal liquors." Thesis, University of Bradford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372179.
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Messenger, Beatrice. "Salivary gland peptide hormones and dietary phenols." Thesis, University of Surrey, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326511.
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Mitchell, Lindsay. "Phenols and tannins of apples and ciders." Thesis, University of Surrey, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322461.
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12
Mordacque, Olivier Michel André. "Selective alkylation of phenols using solid catalysts." Thesis, University of York, 2003. http://etheses.whiterose.ac.uk/14186/.
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Alkylphenols are important industrial chemicals used in a wide range of applications. In particular, 2,6-ditertbutylphenol is an indispensable building block for anti-oxidants and light protective agents. A new solid catalyst was prepared, characterised and tested for the alkylation of phenols with alkenes in an attempt to reduce the environmental hazards associated with the aqueous wastes generated by the homogeneously catalysed alkylation reactions. The new silica gel supported aluminium phenolate catalyst was prepared by a two steps procedure, first grafting of an aluminium precursor such as aluminium trichloride or triethyl aluminium onto silica mainly through reaction with the support silanol groups, then exchange of the aluminium ligand with phenol. Catalysts exhibited mainly Lewis acidity and two types of active sites were detected. The new catalyst was successfully applied in the phenol - isobutene alkylation system. Catalysts exhibited an ortho- selectivity for the introduction of the first tertbutyl group. The selectivity of the second alkylation could be tuned by varying reaction conditions (reaction temperature, catalyst amount, alkene addition methods) and catalyst characteristics (support surface pre-treatment temperature, aluminium precursor and loading). Hence high yields of 2,4-ditertbutylphenol or moderated yields of 2,6-ditertbutylphenol were obtained. Alkylation of phenol with other alkenes and cresols alkylations were successfully catalysed by the new silica gel supported aluminium phenolate catalyst with the same selectivity. However, the diorthopropylphenol was the main dialkyl products when using propene as alkylating agent. "Greening" of the catalyst preparation by reducing the amount of solvent used was carried out without changing the selectivity and the activity of the catalyst. Reusability of the catalyst was investigated and a decrease of activity was observed. Storage of the catalyst was possible for a long time but activity and selectivity were affected.
13
Akgul, Yucel. "Effects of the common pesticide methoxychlor on ovarian steroidogenesis." Morgantown, W. Va. : [West Virginia University Libraries], 2007. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5391.
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Small, Pamela Beth. "Development of a Soy-blueberry Burger and the Changes in Anthocyanins and Phenolics During Storage and Broiling." Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/SmallPB2007.pdf.
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Koopmann, Ricarda. "Allelopathic effects of bark phenols on epiphytic lichens." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=977662861.
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Irebo, Tania. "Proton-Coupled Electron Transfer from Hydrogen-Bonded Phenols." Doctoral thesis, Uppsala universitet, Kemisk fysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-112060.
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Proton-coupled electron transfer (PCET) is one of the elementary reactions occurring in many chemical and biological systems, such as photosystem II where the oxidation of tyrosine (TyrZ) is coupled to deprotonation of the phenolic proton. This reaction is here modelled by the oxidation of a phenol covalently linked to a Ru(bpy)32+-moitey, which is photo-oxidized by a laser flash-quench method. This model system is unusual as mechanism of PCET is studied in a unimolecular system in water solution. Here we address the question how the nature of the proton accepting base and its hydrogen bond to phenol influence the PCET reaction. In the first part we investigate the effect of an internal hydrogen bond PCET from. Two similar phenols are compared. For both these the proton accepting base is a carboxylate group linked to the phenol on the ortho-position directly or via a methylene group. On the basis of kinetic and thermodynamic arguments it is suggested that the PCET from these occurs via a concerted electron proton transfer (CEP). Moreover, numerical modelling of the kinetic data provides an in-depth analysis of this CEP reaction, including promoting vibrations along the O–H–O coordinate that are required to explain the data. The second part describes the study on oxidation of phenol where either water or an external base the proton acceptor. The pH-dependence of the kinetics reveals four mechanistic regions for PCET within the same molecule when water is the base. It is shown that the competition between the mechanisms can be tuned by the strength of the oxidant. Moreover, these studies reveal the conditions that may favour a buffer-assisted PCET over that with deprotonation to water solution.
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Yang, Yun. "Temperature dependent PCDD/PCDF product distributions from phenols." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/20182.
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Semple, Kirk Taylor. "The biodegradation of phenols by a eukaryotic alga." Thesis, University of Newcastle Upon Tyne, 1994. http://hdl.handle.net/10443/374.
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Axenic cultures of Chiamydomonas ulvaensis [CCAP 11/58], Scenedesmus brasiliensis [CCAP 276/1 B] and Ochromonas danica [0CAP933/28] were screened for their ability to grow on and remove phenol from their incubation media. Neither C. ulvaensis nor S. brasiliensis removed the phenol substrate as rapidly as 0. danica which is a nutritionally versatile chrysophyte. 0. danica was found to grow on phenol and p-cresol as the sole C-source at concentrations up to 4mM in cultures grown in both photoheterotrophic and heterotrophic conditions. The alga would not grow on cresols or xylenols unless phenol was present. Oxygen uptake and turnover studies confirmed that the enzymes involved in phenolic catabolism were inducible and that the organism showed a decrease in activity resulting from the position and number of the methyl substituents on the aromatic ring. [U- 14C]Phenol was completely mineralised with some 65% of the 14C-label appearing as 14CO2, approximately 12% remaining in the aqueous medium and the rest accounted for in the biomass. Analysis of the biomass showed that 14C-label had been incorporated into the protein, nucleic acid and lipid fractions; phenol carbon is thus unequivocally assimilated by the alga. Phenol-grown cultures of 0. danica converted phenol to catechol which was further metabolised by the meta cleavage pathway. 2-Hydroxymuconic semialdehyde and pyruvate, characteristic products of meta cleavage, were found in incubations of catechol with cell-free extracts of phenol-grown cells together with the appropriate enzyme activities. This is , as far as I am aware, the first definitive identification of the meta cleavage pathway for aromatic ring degradation in a eukaryotic microorganism.
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Wells, Geoffrey. "Chemical diversity from the oxidation of bioactive phenols." Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324523.
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Nelson, Lisha. "The production of volatile phenols by wine microorganisms." Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/3101.
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Thesis (MScAgric (Viticulture and Oenology))--Stellenbosch University, 2008.The production of good quality wine is essential to ensure competitiveness on an international level. Wine quality is usually evaluated for the visual, olfactory and taste characteristics of that specific wine. The winemaking process starts with the grapes in the vineyard followed by oenological practises in the winery until the final wine is bottled. Factors that could influence wine quality include the grape quality from which the wine is made and different techniques used during wine production. Other factors include the presence as well as the interaction between microorganisms found in the grape juice and wine, and the biochemical effect these microorganisms have on certain chemical compounds in the wine. The different microorganisms found in grape juice and wine can either have a negative or positive contribution to the final quality of the wine. During certain stages of the winemaking process the growth and metabolic activity of certain microorganisms is a necessity to produce good wine. During other stages the presence of certain microorganisms can lead to the development of compounds that is regarded as off-flavours and therefore lead to unpalatable wines of low quality. Yeast strains that naturally present on the grapes and in the winery can also contribute to the final quality of the wine. Brettanomyces yeasts are part of the natural flora of winemaking and can drastically influence the aroma characters of a wine through the production of volatile phenols. The general aroma descriptions of volatile phenols include "smoky", "spicy", "barnyard", "animal" and "medicinal". Although some wine drinkers believe that these characters can add to the complexity of a wine, high levels of volatile phenols is mostly regarded as off-flavours and mask the natural fruity flavours of a wine. With this study we wanted to generate a better understanding of the effect of different winemaking practises on the production of volatile phenols by B. bruxellensis. We evaluated the difference in volatile phenol production when B. bruxellensis was introduced before or after alcoholic fermentation. We have shown that B. bruxellensis could grow and produce volatile phenols during alcoholic fermentation. Results obtained also showed that commercial wine yeast strains could produce the vinyl derivatives that serve as precursors for Brettanomyces yeast to produce the ethyl derivatives. The commercial yeast strains differed in their ability to produce vinyl derivatives. Different malolactic fermentation scenarios were evaluated, namely spontaneous versus inoculated, and with or without yeast lees. Results showed that spontaneous malolactic fermentation had higher volatile phenol levels in the wine than inoculated malolactic fermentation. The treatment with lees reduced the level of volatile phenols, probably due to absorption by yeast cells. The presence of the phenyl acrylic decarboxylase (PAD1) gene and the production of volatile phenols by S. cerevisiae commercial yeast strains were evaluated in Shiraz grape juice and in synthetic grape juice. The results indicated that the yeast strains differ in their ability to produce 4-vinylphenol and 4-vinylguaiacol. All the yeast strains tested had the PAD1 gene. We also evaluated the presence of the phenolic acid decarboxylase (padA) gene and the ability of different lactic acid bacteria strains to produce volatile phenols in synthetic wine media. Although some of these strains tested positive for the phenolic acid decarboxylase gene most of them only produced very low levels of volatile phenols. This study made a valuable contribution on the knowledge about the effect of Brettanomyces yeast on the volatile phenol content of red wines during different stages of the winemaking process and when applying different winemaking practices. It also showed the effect between Brettanomyces yeast and other wine microorganisms and the possible influence it could have on the final quality of wine. Research such as this can therefore aid the winemaker in making certain decisions when trying to manage Brettanomyces yeast spoilage of wines.
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Allott, Philip Hugh. "The thermochemistry of bromination of phenols and anilines." Thesis, Royal Holloway, University of London, 1986. http://repository.royalholloway.ac.uk/items/45ee4bfb-9be1-4500-9d03-2b883899c5cb/1/.
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A method has been developed for bromination of aromatic compounds in aqueous solution in an isoperibol calorimeter. The enthalpies of bromination of phenol to 2,4,6-tribromophenol and of aniline, 2-bromo-aniline, 4-bromoaniline and 2,4-dibromoaniline to 2,4,6-tribromo-aniline were measured using this method. These values were used to derive the standard enthalpies of formation of 2,4,6-tribromophenol, 2-bromoaniline, 4-bromoaniline, 2,4-dibromoaniline and 2,4,6-tribromo-aniline. The enthalpies of combustion of 2,4,6-tribromophenol and 2,4,6-tribromoaniline were measured using a rotating-bomb calorimeter. These values were used to derive the standard enthalpies of formation of 2,4,6-tribromophenol and 2,4,6-tribromoaniline. The discrepancy between these latter standard enthalpies of formation and those found using the solution calorimetric method is discussed, and possible sources of systematic error indicated. The solution calorimetric method was adapted for the thermometric titration of phenols in aqueous solution with an aqueous solution of bromine. The sequential nature of bromination of five compounds -phenol, 2-bromophenol, 2-methylphenol, 3-methylphenol and 2-hydroxy-benzoic acid - was investigated using this technique. The reasons for this sequentiality are discussed. abstract continued overleaf A complete data-processing system has been designed for the solution calorimeter. A microcomputer is used for data acquisition from the AC bridge of the calorimeter through an analogue-to-digital interface. The bridge voltage readings, once uploaded to a minicomputer, are processed to yield the corrected temperature change. Enthalpies of reaction can then be calculated and statistical analyses performed. The problems encountered in developing the system are discussed, especially with regard to the calculation of the corrected temperature change from the noisy temperature data. A least-squares cubic spline is used for curve-fitting and calculation of the first derivative of temperature versus time.
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Amiri, Fariba. "Influence of pH and NOM on Sorption of Phenols onto Aquifer Material." Doctoral thesis, Technische Universität Dresden, 2004. https://tud.qucosa.de/id/qucosa%3A24473.
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Geosorption processes play an important role as retardation mechanism in subsurface transport of organic water constituents. Geosorption behaviour of Ionisable Hydrophobic Organic compounds (IHOCs) especially influence of dissolved natural organic materials on their sorption coefficients is poorly investigated. In this study influence of pH and NOM on the sorption of three different phenols (2-methyl-4,6-dinitrophenol, 2,4,6-trichlorophenol and pentachlorophenol) on a natural sandy aquifer material collected from a bank filtration site was studied in flow through column experiments. In first step the sorption coefficients of investigated phenols from NOM-free solutions with different pH values were determined. Single as well as multi (mixed) solutes experiments confirmed that there was no competition effect among the phenols investigated. An increasing sorption/retardation was observed with decreasing pH. A linear model was used to resolve the apparent sorption coefficient into an ionised species and neutral species component. This model allows a prediction of apparent sorption coefficients for any pH value. Analysis of data also revealed that the anion of 2-M-4,6-DNP show no significant sorption and a simple model based on the neutral form sorption coefficient was useful in predicting the apparent sorption coefficient over the entire pH range investigated. For 2,4,6-TCP and PCP, the anion sorption is much lower than that of the neutral species but cannot be neglected completely. For PCP, the anion sorption is even as high as the sorption of neutral 2,4,6-TCP. Thus for such hydrophobic phenols prediction of sorption based only on the partitioning of non-dissociated species may lead to an error, especially at high pH values (> pKa), where ionised form is present predominantly. On the other hand prediction of sorption based on the partitioning of non-dissociated species is useful at pH < pKa or in cases where the anion sorption can be neglected. The advantage of this prediction is that it allows predicting the pH-dependent sorption only on the basis of LFER correlations. It was shown that the organic carbon normalized sorption coefficients of the neutral forms of the phenols can be predicted better by solubility based regression correlations than by n-octanol-water partition coefficient based correlations. In second step the apparent sorption coefficients of investigated phenols from NOM-containing solutions (mixed solution of phenols dissolved in natural river water) with different pH values were determined; the sorption coefficients obtained from this step were compared with the results of the first step examinations. Analysis of data revealed that binding of 2-M-4,6-DNP by dissolved humic substances (DHS) reduces the sorption coefficient significantly. In contrast to it, the sorption of the more hydrophobic chlorinated phenols was not affected by DHS. A strong reduction of sorption onto aquifer material caused by complex formation with DHS was also observed for a second nitrophenol (2,4-DNP) and seems to be typically for nitrophenols. A combined sorption and complex formation model was proposed which could be used successfully to describe the effect of pH and NOM concentration on sorption reduction and to estimate binding constants. The binding constant found for 2-M-4,6-DNP is much higher than those reported by Ohlenbusch and Frimmel, 2001, for chlorophenols associated with Aldrich humic acid. This can be interpreted as a result of specific interactions between the nitrophenol and DHS. This phenomenon may cause an increase of the amount of nitrophenols, which can be transported with the groundwater flow and has to be considered in transport modelling, especially in cases where pH is lower than pKa. The models developed here are a useful tool to describe the influence of pH and NOM on geosorption processes and to estimate the Kd values which have to be used in transport models.
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Kalili, Kathithileni Martha. "Application of comprehensive 2-dimensional liquid chromatography for the analysis of complex phenolic fractions." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/2420.
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Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2009.ENGLISH ABSTRACT: The separation of apple, cocoa and green tea phenolic compounds by comprehensive 2-dimensional liquid chromatography (2-D-LC) has been studied. In the first dimension, phenolic compounds were separated according to polarity by hydrophilic interaction chromatography (HILIC) on a diol stationary phase with a mobile phase containing acetonitrile, methanol, acetic acid and water. Gradient reversed-phase (RP) LC using a C18 column with fluorescence detection was employed in the second dimension to separate compounds according to hydrophobicity. Compounds were identified using negative electrospray ionisation mass spectrometry (ESI-MS) coupled to both HILIC and RP separations. The coupling of HILIC and RP separations proved to be especially beneficial since this provided simultaneous information on both the polarity and hydrophobicity of phenolics. The low degree of correlation (r2 < 0.21) between the two LC modes afforded peak capacities in excess of 3000 for the off-line method. An on-line method was also developed utilizing a short, small particle-packed column to provide fast separation in the second dimension. A 1 mm i.d. column was used in the first dimension for the on-line system to reduce injection volumes onto the second dimension column. A significantly lower practical peak capacity was measured for the on-line system, due largely to the reduction in second dimension peak capacity. On the other hand, analysis could be performed in an automated fashion using the online system reducing the risk of sample alteration and guaranteeing better operation reliability and reproducibility. Especially the off-line comprehensive HILIC × RP-LC method developed demonstrated its utility in the analysis of various groups of phenolic compounds including proanthocyanidins, phenolic acids, flavonols and flavonol conjugates in a variety of natural products.
AFRIKAANSE OPSOMMING: Die skeiding van fenoliese komponente in appel, kakao en groen tee is deur middel van ‘comprehensive’ 2-dimensionele vloeistof chromatografie (2-D-LC) bestudeer. Hidrofiliese interaksie chromatografie (HILIC) is gebruik om die fenoliese komponente in die eerste dimensie te skei op grond van polariteit, deur gebruik te maak van ‘n diol stationêre fase en mobiele fase bestaande uit asetonitriel, metanol, asynsuur en water. ‘n Gradiënt omgekeerde fase (RP) LC analisie op ‘n C18 kolom met fluorosensie deteksie is in die tweede dimensie gebruik om fenole volgens hidrofobisiteit te skei. Negatiewe elektrosproei-ionisasie massa spektometrie (ESIMS) gekoppel aan HILIC en RP skeidings is gebruik vir identifikasie van fenole. Die koppeling van HILIC en RP skeidings veral voordelig deurdat dit gelyktydige informasie verskaf het oor die polariteit sowel as die hidrofobisiteit van die fenoliese komponente. Die lae graad van korrelasie (r2 < 0.21) tussen die twee LC metodes was verantwoordelik vir piek kapasiteite bo 3000 vir die af-lyn metode. ‘n Aanlyn metode was ontwikkel deur gebruik te maak van ‘n kort, klein partikel gepakte kolom om vinnige skeiding in die tweede dimensie te verseker. 1 mm i.d. kolom was gebruik in die eerste dimensie vir die aanlyn sisteem om die inspuit volume op die tweede dimensie kolom te verminder. Aansienlike laer praktiese piek kapasiteit was gemeet vir die aanlyn sisteem, grootliks toegeskryf aan die reduksie in die tweede dimensie piek kapasitiet. Aan die ander kant, analise kan geoutomatiseerd uitgevoer word deur gebruik te maak van die aanlyn sisteem, wat monster alterasie, beter betroubaarheid en reproduseerbaarhied verseker. Veral die ontwikkelde af-lyn ‘comprehensive’ HILIC × RP-LC metode toon demonstreerbare voordele vir die analiese van verskeie groepe fenoliese komponente, insluitende proantosianiede, fenoliese sure, flavonole en gekonjugeerde flavonole in ‘n verskeidenheid natuurlike produkte.
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Marshall, Laura. "Novel methodology for the synthesis of ¹³C-labelled phenols and its application to the total synthesis of polyphenols /." St Andrews, 2010. http://hdl.handle.net/10023/875.
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Hoffmann, Petra. "The development and evaluation of procedures for the synthesis of phenolic ethers by Baeyer-Villiger oxidation." Thesis, Port Elizabeth Technikon, 2001. http://hdl.handle.net/10948/51.
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A novel preparative method has been discovered in our laboratories which produces hydroxy-substituted phenolic ethers in a simple one-pot process. Initially it was found that 4-hydroxyacetophenone, when oxidized in the presence of ammonium peroxydisulfate and concentrated sulfuric acid in methanol, resulted in 4- methoxyphenol as product in high yield. Being novel, no information about the method was available in the literature, and hence it was our task to study the reaction more extensively. The scope of the reaction was investigated in that different reagents and substrates, as well as alternative oxidants, catalysts and alcohols (or reagents which may be envisaged to behave similarly to alcohols) were used. The studies showed that 4- hydroxy-substituted benzaldehyde and acetophenone, vanillin, fuchsones and stilbenequinones as substrates all successfully afforded the phenolic ether. Other oxidants such as hydrogen peroxide, sodium perborate etc. also afforded the phenolic ether but were less effective. The use of other acids than sulfuric acid resulted in comparable or lower yields of the desired phenolic ether. When the use of alcohols or similar reagents was varied, it was found that methanol, ethanol, benzyl alcohol, allyl alcohol, but-3-en-1-ol, hex-5-en-1-ol and undec-10-en-1-ol all afforded the desired ethers in significant yields. In an investigation to determine how this method may be useful for industrial applications, it was observed that compounds such as 3,5-di-tert-butyl-4-hydroxysubstituted alkenyloxy phenols, having potential application as antioxidant precursors in the polymer industry, may be prepared. Results showed that the reaction became less efficient when the alkenyl chain length was increased. The use of different acids and oxidants, the change of the oxidant:substrate ratio and the addition of a potential lanthanide catalyst did not improve the yield of the desired ether. A mechanism for the reaction was proposed which involved an initial Baeyer-Villiger oxygen insertion step to afford an ester which was hydrolysed in situ to hydroquinone. The remaining oxidant was then involved in oxidizing some of the soformed hydroquinone to benzoquinone. It was then proposed that these two compounds, i.e., hydroquinone and benzoquinone, interacted with each other in solution, forming a charge-transfer complex. According to our proposal, the carbonyl group of the benzoquinone, when complexed with hydroquinone in solution, was then attacked by nucleophilic reagents such as alcohols. Etherification hence resulted as a consequence of this attack. A statistical experimental evaluation and optimization study was then performed which led to a system that produced the phenolic ether, 4-methoxyphenol, in an 86% yield. An analysis of the effects of the reaction parameters on the reaction showed that the reaction temperature and the oxidant:substrate ratio played a major role in deciding the effectiveness of the reaction, while the amount of substrate and acidic catalyst had a much smaller influence on the ether yields.
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Mitchell, Anthony Stewart, and mikewood@deakin edu au. "Synthetic studies towards anthraquinones." Deakin University. School of Biological and Chemical Sciences, 1994. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20051017.151445.
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The oxidation of substituted phenols with phenyliodonium diacetate in methanol was found to afford 2,4-cyclohexadienones, 2,5-cyclohexadienones or mixtures of isomers depending on the substrate being oxidized. A reaction mechanism was proposed for this oxidation which involved an intermediate aryloxenium ion. A strong correlation was observed between the experimentally determined product ratios and the results predicted by calculation of the LUMO coefficients of the proposed intermediates,
Annulation of these cyclohexadienones with the anion derived from cyanophthalide afforded substituted anthraquinones in high yields. The chemistry relating to the annulation of Michael acceptors with phthalide anions was comprehensively reviewed.
A mild selective method for the oxidation of hydroquinones to quinones using dibenzoyl peroxide and base is presented.
A general synthetic approach to C-glycosylanthraquinones was presented, based on the annulation of a C-glycosylcyclohexadienone with the anion derived from cyanophthalide, A suitable precursor to a C-glycosylcyclohexadienone, 2-(2,3,4,6-tetra-0-acetyl-|3-D-glucopyranosyl)benzyloxybenzene, was prepared via the reaction of benzoylbromoglucose with 2-benzyloxyphenylmagnesium bromide,
A group of molecules were prepared by a Marschalk reaction between /ewcoquinizarin and aldehydo-sugsrs. These compounds are potential bioreductive alkylating agents in which molecular simplicity can be achieved without overly sacrificing DNA binding ability.
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Zhu, Fan, and 朱帆. "Interactions of carbohydrates with phenolic compounds." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B45584710.
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Bifulco, Laura. "Development of electrochemical and microbial sensing systems for detection of phenolic compounds." Thesis, Cranfield University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269525.
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Setälä, Harri. "Regio- and stereoselectivity of oxidative coupling reaction of phenols : spirodienones as construction units in ligin /." [Espoo, Finland] : VTT, 2008. http://www.vtt.fi/inf/pdf/publications/2008/P689.pdf.
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Chan, On-chim. "Toxicity of phenol to anaerobic biogranules in shock and in continuous loading conditions /." Hong Kong : University of Hong Kong, 1996. http://sunzi.lib.hku.hk/hkuto/record.jsp?B18037951.
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Mordocco, Angela Maria. "Continuous degradation of phenol at low levels using Pseudomonas putida immobilised in calcium alginate /." [Campbelltown, N.S.W. : The Author], 1996. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030710.134758/index.html.
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Hoffmann, Eric. "The oxidative coupling of phenols using stoichiometric metal oxidants." Thesis, Nelson Mandela Metropolitan University, 2005. http://hdl.handle.net/10948/180.
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The oxidative coupling of 2,6-di-t-butylphenol under mild reaction conditions is well documented and the subject of many patents. However, the coupling of other monoand di- substituted phenols is not as well documented and thus there is scope for further investigation for providing a convenient, environmentally friendly and economically viable method for the oxidative coupling of these phenols. In this study, the oxidative coupling of a variety of alkylated phenolic substrates, 2-tbutylphenol, 2,6-di-t-butylphenol, 2,4 -di-t-butylphenol and ,4-dimethylphenol, using a range of different oxidizing agents, were investigated by means of experimental and/or theoretical means. The dibutylated aromatics provided the highest selectivities to their respective coupled products, with results obtained with the dimethyl analogue being only satisfactory, and that for 2 -t-butylphenol being totally inefficient. PM3 Molecular orbital (MO) calculations were used to predict the possible modes of coupling for the substrates 2,6 -di-t-butylphenol and 2,4-di-t-butylphenol, and these results were then compared with those obtained experimentally in the laboratory. Preliminarily, the coupling of unsubstituted phenolics was also assessed by means of MO calculations. Much emphasis was placed on Ce(IV) as the oxidant, and the reaction conditions under which it was used and the results that were obtained have not been reported before and are therefore novel. The oxidation of 2,4-di-t-butylphenol using Ce(IV) in the presence of methanesulphonic acid was optimized to afford high yields and selectivities to the desired ortho C-ortho C coupled product under mild reaction conditions. Various reaction parameters were also investigated in this case, such as varying the MeSO3H concentration, the solvent, the reaction temperature, the reaction time, the substrate loading, the rate of oxidant addition and the substrate to oxidant ratio. Ce(IV) also gave a high selectivity to the para C-para C coupled product when IX using 2,6-di-t-butylphenol as the substrate. However, it was not as effective with 2,4- dimethylphenol, and even less so with 2-t-butylphenol. The oxidation reactions of 2-t-butylphenol and 2,4-dimethylphenol with various coupling agents were also investigated with the intention of obtaining high selectivities to the respective desired coupled products. In these studies, 2-t-butylphenol afforded a large number of products, irrespective of the oxidant used. The dimethyl analogue was more selective, but results were not optimal. It was clear that the number of substituents on the phenol ring, their nature and their position with regards to the hydroxyl moiety was of great importance and made a significant impact on the preferred coupling mode of the substrate. It was observed that steric effects also played a major role in the outcome of these reactions: 2,6-di-t-butylphenol never afforded any C-O coupled products whereas 2-t-butylphenol, 2,4-di-t-butylphenol and 2,4-dimethylphenol all appeared to undergo some C-O coupling. Finally, reaction mechanisms were provided for both the K3Fe(CN)6 and Ce(IV) work, these reacting in basic and acidic media, respectively. It was proposed that both of these mechanisms operate through the initial formation of the phenoxyl radical.
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Ikehata, Keisuke. "Characterisation of tyrosinase for the treatment of aqueous phenols." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0027/MQ50624.pdf.
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Wagner, Monika. "Horseradish peroxidase-catalyzed removal of phenols from industrial wastewaters." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38095.
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Horseradish peroxidase (HRP) enzyme catalyzes the oxidation of aqueous phenols by hydrogen peroxide resulting in the formation and precipitation of polymeric products. The technical feasibility of this enzymatic process for the treatment of industrial wastewaters that contain phenols was investigated. Bench-scale experiments were conducted in which the influences of selected components in the waste matrix on treatment efficiency were assessed.Experiments with synthetic phenol solutions revealed that the toxicity of HRP-treated phenol solutions declines with time and is dependent on the presence of protective additives, the mode of reagent addition, and the presence of wastewater constituents. Also, many phenolic solutions can be completely detoxified by providing an additional dose of hydrogen peroxide after the completion of the enzymatic reaction. Chitosan was found to be an effective additive for reducing the amount of enzyme required to accomplish phenol transformation in synthetic and actual wastewaters.
HRP was able to accomplish the treatment of phenols in the presence of a wide range of concentrations of suspended solids, salts, metals, and other inorganic and organic species that are frequently present in industrial wastewaters. In certain instances, treatment was more effective in a real waste matrix as compared to the treatment of pure solutions of phenol due to the presence of particular waste components. However, sulfide, manganese(II) and low quantities of cyanide negatively impacted upon the enzymatic transformation of phenol.
It was demonstrated that actual industrial wastewaters collected from pulp and paper production and petroleum refining operations could be treated with HRP and H2O2 to meet regulatory discharge limits for phenol. The enzymatic process can selectively target phenols, which are a major source of toxicity in the wastes, for treatment. Treatment of real wastewaters may require higher than stoichiometric doses of hydrogen peroxide due to the inherent peroxide demand of reduced wastewater constituents or catalytic decomposition of peroxide. HRP-treatment improved wastewater quality as reflected in a significant toxicity reduction. It can also result in a substantial decrease in the biochemical and chemical oxygen demands.
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Long, Philip. "Rhodium-phosphinite catalysts for the ortho-arylation of phenols." Thesis, University of Bristol, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.529840.
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Bollard, Mary Elizabeth. "NMR spectroscopic investigations into the metabolism of substituted phenols." Thesis, Birkbeck (University of London), 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264929.
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Al-Obaidi, U. "Nitrous acid catalysed nitration of phenols in sulphuric acid." Thesis, University of Exeter, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373818.
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Owen, Nicholas D. S. "The H-bonding activity of F'- with some phenols." Thesis, University of York, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280440.
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Newby, Craig Sinclair. "The pro-inflammatory effects of phenols on the skin." Thesis, King's College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314177.
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Oble, Julie. "Nouvelles réactions multicomposant avec des phenols et des isonitriles." Palaiseau, Ecole polytechnique, 2007. http://www.theses.fr/2007EPXX0017.
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Au cours de cette thèse, nous avons découvert que des phénols pauvres en électrons comme les nitrophénols ou le salicylate de méthyle peuvent intervenir comme partenaire acide dans des couplages de type Ugi. Ces phénols sont en effet suffisamment acides pour activer les imines intermédiaires et déplacer l'ensemble des équilibres par un réarrangement de type Smiles. Il est ainsi possible d'obtenir des N-arylaminoamides par un couplage multicomposant entre une amine primaire, un isonitrile, un composé carbonylé et un phénol. Par la suite, nous nous sommes intéressés à la possibilité d'étendre cette réaction à d'autres phénols appauvris tels que des phénols hétérocycliques comme, par exemple, les hydroxy pyridines ou pyrimidines permettant la formation de composés intéressants d'un p!oint de vue biologique. Ces réactions permettent d'envisager des synthèses rapides et efficaces de composés hétérocycliques. Ainsi nous avons mis au point une synthèse « one-pot » de benzopyrazinones par hydrogénolyse cyclisante avec d'excellents rendements. Couplée à une métathèse cyclisante, cette réaction permet d'envisager une synthèse efficace de composés hétérocycliques de type pyrimidine-azépines, avec mise en évidence lors de la cyclisation d'un tandem RCM isomérisation de la double liaison.
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Wisniewski-Dyé, Florence. "Induction des genes de virulence chez agrobacterium tumefaciens : activite de phenyl-glycosides et purification d'une proteine affine de phenols." Orléans, 1995. http://www.theses.fr/1995ORLE2044.
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L'interaction entre agrobacterium tumefaciens, bacterie du sol, et les cellules vegetales est le seul exemple naturel de transfert d'adn entre un procaryote et un eucaryote. Ce processus complexe aboutit a la formation d'une tumeur, la galle du collet (crown gall), maladie agronomique importante qui affecte la plupart des plantes dicotyledones. D'autre part, cette bacterie est largement utilisee pour transformer genetiquement des vegetaux par l'introduction de genes d'interet agronomique. L'expression des genes de virulence de la bacterie, induite par des composes phenoliques (comme l'acetosyringone ou l'alcool coniferylique), est l'etape cle de ce processus de transformation. Au cours de ce travail, nous nous sommes interesses a la synthese de nouveaux composes phenoliques glycosyles, molecules signal potentielles. L'alcool coniferylique, un precurseur de lignine, a ete couple sur le d-glucose, le d-galactose et le l-fucose pour former des coniferyl-o-glycosides. L'activite inductrice de ces composes a ete etudiee sur deux souches d'a. Tumefaciens portant le gene rapporteur de la -galactosidase d'e. Coli sous la dependance d'un promoteur des genes de virulence. L'activite des derives glucosyle et galactosyle doit etre reliee a la presence d'osidases specifiques chez les bacteries, menant a une hydrolyse prealable du compose glycosyle. Outre une specificite vis-a-vis de la partie osidique, les osidases bacteriennes rencontrees montrent une specificite etroite vis-a-vis de la partie aglycone. L'ose et le phenol ainsi liberes peuvent agir en synergie pour induire les genes de virulence. Des composes de synthese non hydrolysables, des thio-glycosides de l'acetosyringone, montrent egalement une activite inductrice des genes de virulence. Parmi les diverses caracteristiques structurales associees aux proprietes inductrices, ces thio-glycosides presentent une fonction phenol libre. La derniere partie de notre travail s'est focalisee sur la caracterisation et la purification des recepteurs potentiels pour des composes phenoliques. L'acide syringique, par la presence d'une fonction acide carboxylique dans sa structure, a ete greffe sur une matrice d'affinite par l'etablissement d'une liaison amide sur un bras intermediaire. Nous avons montre au prealable que l'introduction d'une fonction amide dans ce compose n'abolissait pas les proprietes inductrices et donc l'interaction avec un recepteur potentiel. Le support chromatographique a permis d'isoler par elution specifique, une proteine de mr 39 kda et de pi 4,3. Cette proteine pbp39 pourrait etre localisee dans l'espace periplasmique mais son implication directe dans la perception des phenols reste a demontrer
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Ali, Haroon. "Protein-phenolic interactions in food." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=32748.
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Our objective was to investigate the mode of interaction between selected food proteins and phenolic compounds. Bovine serum albumin (BSA), bovine beta-lactoglobulin, and soybean glycinin were used with the following phenolic compounds; 3,4,5-trihydroxybenzoic acid (gallic acid), 3,4-dihydroxy cinnamic acid (caffeic acid), p -hydroxycinnamic acid (courmaric acid), and 5,7-dihydroxy 4-methoxy isoflavone (biochanin A). The interaction was investigated using incubation temperatures of 35°, 45° and 55°C at pH 5, 7 and 9. Native and SDS-polyacrylamide gel electrophoresis (PAGE), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) spectroscopy were used to identify protein-phenol interactions. Certain phenolic compounds combined with BSA and prevented protein aggregation. In general, the thermal stability of the proteins increased as a result of interaction with phenolic compounds; the most pronounced effect was observed with beta-lactoglobulin in the presence of gallic acid at pH 7. The interaction of the phenols with the proteins resulted in changes in protein secondary structure. (Abstract shortened by UMI.)
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Yiannakakis, Alexandros Emmanuel 1959. "Adsorption/desorption of phenols on the Pima clay loam soil." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276709.
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A linear distribution isotherm described the sorption/desorption of four phenols on the Pima clay loam soil. The linear distribution coefficients for 2,4-dichlorophenol, 2-chlorophenol, phenol and 2,4,6-trichlorophenol were 3.61, 2.93, 0.87, and 0.79. Ionization of the phenols affected their relative distribution order. Hydrogen bonding of phenols to exposed mineral sites accounted for the greater measured sorption than was predicted. The effect of solid concentration on the distribution of phenols was tested over a 10-fold soil/solution range. When a log transformation was performed on the data, a highly significant inverse relationship existed between the distribution of phenols and the soil/solution ratio. A 3-fold increase in the dissolved organic carbon in solution was associated with the decrease in the distribution coefficient. A 3-fold increase in the fraction organic carbon in the soil occurred when dry sludge solids were added to the Pima soil. A substantial increase in the dissolved organic carbon in solution was associated with the addition of sludge solids to the soil. (Abstract shortened with permission of author.)
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Fogel, Ronen. "Fundamental investigations into the factors affecting the response of laccase-based electrochemical biosensors." Thesis, Rhodes University, 2011. http://hdl.handle.net/10962/d1007166.
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Given their widespread effects and distribution in both natural and industrial environments, the monitoring of phenolic compounds is of considerable analytical interest. Electrochemical biosensor technologies, in particular those comprising laccase enzymes, afford many potential benefits to address this analytical need. However, several key factors affecting sensor response currently limit their applicability. This Thesis reports on the fabrication and optimisation of an electrochemical laccase-based biosensor towards the application of the monitoring of phenolic compounds. Selected factors considered to affect sensor response were investigated using the optimised biosensor. These included: electrochemical, biochemical and substrate-dependent factors, which were found to intersect in modulating biosensor response signals. Through the application of transducer-dependent and substrate-dependent parameters, the selective and simultaneous detection of a mixture of different phenolic analytes is successfully demonstrated. This Thesis also investigates the use of Quartz-Crystal Microbalance with Dissipation (QCM-D) technology, an analytical technique that measures physical parameters of thin-film structures, towards the successful monitoring of enzyme immobilisation strategies. These strategies are fundamental to the successful fabrication of biosensors, and the real-time monitoring of immobilised film formations is of considerable research interest. In the studies reported on in this Thesis, QCM-D technology was demonstrated to be an effective complementary technology in the prediction of film immobilisation techniques on the resultant biochemical kinetics of immobilised enzymes.
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Cakir, Esra. "Varietal differences in antioxidant activity and phenolic composition of asparagus." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Thesis/Summer2007/e_cakir_062107.pdf.
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Bourne, Thomas Franklin. "Biodegradation of keratins and phenolic compounds." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/25403.
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Alu'datt, Muhammad Hussein. "Phenolic compounds in oil-bearing plants and their interactions with oilseed protein isolates." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=102950.
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Oil-bearing plants are important sources of edible oil and proteins; they have attracted attention recently because of their antioxidant, antimicrobial and anti-inflammatory properties. The objective of this work was to investigate the nature of phenolic compounds in oil-bearing plants and the effects of phenolic compounds on protein isolates from soybean and flaxseed. Proteins were isolated from full-fat and defatted soybean and flaxseed using sodium hydroxide extraction and isoelectric precipitation. Free phenolic compounds were extracted from the oil-bearing plants and protein isolates using methanol; for bound phenolic compounds the oil-bearing plants and proteins were subjected to basic and acidic hydrolysis followed by methanol extraction. Total free and bound phenolic compounds were determined by spectrophotometric analysis. Reversed phase-HPLC was used for separation of individual phenolic compounds, which were identified by mass spectrometry (MS). Molecular characteristics and biological properties of the protein isolates were studied using RP-HPLC, polyacrylamide gel electrophoresis (PAGE) and MS. Thermal and gelation properties of protein isolates were investigated using differential scanning calorimetry (DSC) and rheometry. Generally, bound phenolic compounds (20%-30% of total phenolic content) were higher in protein isolates from flaxseed than in protein isolates from soybean (10%-20% of total phenolic content). With flaxseed protein isolates, removal of phenolic compounds showed little effect on the electropherotic behavior of the proteins or the protein subunits. Native-PAGE. SDS-PAGE and RP-HPLC for the peptides profiles of hydrolyzed protein isolates from both full-fat and defatted soybean revealed the removal of free and bound phenolic compounds affect on the biological properties of protein isolates. Removal of free and bound phenolic compounds affected the thermal stability and gelation properties of protein isolates from flaxseed and soybean.
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Cheng, Ka-wing. "Preventive potential and mechanism of dietary phenolics on the formation of mutagenic heterocyclic amines." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B4284177X.
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Hensler, Sven. "Distribution Coefficients of Ionized and Un-ionized Halogenated Phenols in an Octanol-water System and their Relationship to Molecular Structure." PDXScholar, 1996. https://pdxscholar.library.pdx.edu/open_access_etds/5169.
Full textAbstract:
Life supporting biological membranes are barriers to toxic chemicals. One of the factors determining the toxicity of chemical compounds is their distribution between membranes and their an environment. An octanol-water system is frequently used as a model for biological membranes to estimate the toxic potency of environmental pollutants. The distribution of a chemical between the octanol and the water phase is described by the octanol-water partition coefficient Kow. This study is concerned with the relationship between Kow and the molecular structure of the toxic chemical. In the study the following trihalophenols were included: 2,4,6-trifluorophenol (TriFP), 2,4,6-trichlorophenol (TriCP); 2,4,6-tribromophenol (TriBP) and 2,4,6-triiodophenol (TrilP). The distribution of halophenols between octanol and water was measured as a function of the pH. Experimental results were analyzed in terms of a two compartment distribution model which accounts for the pH dependent dissociation of the trihalophenol. We showed that, with the exception of TriIP, the pH dependence of the distribution coefficient of 2,4,6 trihalophenols can be understood with this model. From the fit of the distribution model to the experimental results, the following log(Kow) of the neutral molecules were determined: 1.96 (TriFP), 3.65 (TriCP}, 4.11 (TriBP) and approximately 4.42 (TrilP). For the ionized species the log(Kow) are 1.38 (TriFP), 0.15 (TriCP), 0.08 (TriBP) and 1.16 (TriIP). In relation with these distribution studies, the following values for the dissociation constants pKa were obtained: 7.12 (TriFP}, 6.15 (TriCP), 5.9 (TriBP) and 6.6 (TriIP). We also found that octanol dissolved in the water phase does not significantly affect the dissociation of TriIP. The relationship between Kaw and trihalophenol molecular structure was studied in two models. Linear relationships were found between log(Kow) and the surface area as well as between log(Kow) and molar volume for both the neutral and the ionized halophenols. It was not possible to discriminate between the two models. Distribution coefficients of the ionized and unionized 2,4,6-trihalophenols are proportional to the each other. The proportionality factor, (3.54±1.49)x104, is a measure of the effect of electric charge on the transfer across the water-octanol interface.
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Word, Robert. "Distribution of Ionized and Neutral Halogenated Phenols in an Octanol-water Membrane Model System." PDXScholar, 1996. https://pdxscholar.library.pdx.edu/open_access_etds/5207.
Full textAbstract:
The accumulation of xenobiotics, such as halogenated phenols, in soils, sediments, and living organisms is primarily a partitioning process between an aquatic and organic phase. It is traditional to use a bulk octanol-water system to model the partitioning of a compound between complex biological lipid membranes and aqueous media. The octanol-water partition coefficient Kow successfully approximates the lipid membrane-water partition coefficient Ki;pw of neutral compounds. However, the ionized species of substituted phenols were shown (Smejtek, et al. 1993; Escher, et al. 1996) to have a higher affinity for lipid membranes than predicted from octanol-water results. Data on the octanol-water partition coefficients of molecular ions is limited. In order to compare the partitioning of neutral and charged species of halogenated phenols between the lipid membrane-water and octanol-water systems, we measured the pH dependent distribution of ionized and neutral 2,3,4,6-tetrachlorophenol (TeCP), pentafluorphenol (PFP), pentachlorophenol (PCP), and pentabromophenol (PBP). For the neutral (HA) species of each phenol, log Kow was found to be 4.28 (TeCP), 2.79 (PFP), 4.77 (PCP), and approximately 4.67 (PBP). For the ionized (A-) species of each phenol, log Kow was found to be 0.48 (TeCP), -0.85 (PFP), 1.16 (PCP), and 1.77 (PBP). These results are compared with sorption data on halophenols in a lipid membrane-water system (Smejtek, et al. 1996). This study shows that ionized halophenols have an affinity for lipid membranes about two to three orders of magnitude greater than for octanol. The usefulness of the octanol-water model as a predictor of lipid membrane-water partitioning for ionizable compounds, such as halogenated phenols, is questioned in view of the present results. Two thermodynamic Kow prediction models based on molecular properties are discussed in the context of the octanol-water partitioning of ionized and neutral compounds. The partition coefficients predicted by the molar volume based model (Gobas, et al. 1988) correlates with the experimental Kow results of this study better than Kow results predicted from the molecular surface area based model (Smejtek, et al. 1996). Results of this study support the hypothesis that partitioning of xenobiotics in the octanol-water system is fundamentally different than partitioning in lipid membrane-water systems.