Dissertations / Theses: 'Cations'

1

DAHHANI, FADIL. "Reactions des cations et cations radicaux en phase gazeuse." Paris 6, 1996. http://www.theses.fr/1996PA066107.

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L'objectif de cette these est l'etude des reactions unimoleculaires et bimoleculaires en phase gazeuse. Elle comporte quatre parties: la premiere presente un expose sur les generalites de la spectrometrie de masse et un apercu sur quelques mecanismes d'isomerisation connus en phase gazeuse et en phase condensee. Les processus d'isomerisation entre cations radicaux solvates et ions -distoniques sont etudies dans une deuxieme partie apres avoir rappele les principales caracteristiques des ions distoniques. Il a ete notamment montre que cette isomerisation a faible energie critique evolue toujours dans le sens exothermique de la reaction: l'isomerisation de ch#3oh#+#. En ion -distonique #. Ch#2oh#2#+ plus stable peut etre catalysee par des neutres appropries, h#2o notamment, alors que la reaction inverse n'est pas observee. L'etude du caractere ambivalent de ch#3och#2#+ a ete traitee dans une troisieme partie. L'analyse des resultats des reactions du cation ch#3och#2#+ avec une serie d'alcools, cetones, aldehydes, diols a montre que ce cation peut avoir le caractere electrophile classique et d'autre part peut etre transporteur du methyle. Enfin dans une quatrieme partie sont rassemblees les differentes techniques utilisees au cours de cette these pour decrire les reactions unimoleculaires et bimoleculaires en phase gazeuse

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2

Kildahl-Andersen, Geir. "Polyenyl cations and radical cations – synthesis, spectroscopic properties and reactions." Doctoral thesis, Norwegian University of Science and Technology, Department of Chemistry, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1790.

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In the present work, polyene precursors for the formation of charged polyenyl species were synthesised. Their conversion to charge delocalised radical cations and diamagnetic mono- and dications was carried out by treatment with Brønsted and Lewis acids. Reaction conditions were optimised to achieve sufficient stability of the charged polyenes for characterisation by modern spectroscopic methods; in particular nearinfrared absorption spectroscopy (NIR), two-dimensional nuclear magnetic resonance (2D NMR), electron paramagnetic resonance (EPR) and dynamic light scattering.

The full assignment of ¹³C NMR chemical shifts of mono- and dications was used as basis for charge distribution estimates in charge delocalised polyenes. Coulombic repulsions are dominant features in dicationic systems, whereas monocations show a more even distribution of charge throughout the polyene system. The size limit of charge delocalisation regions, suggested by current theories, has been investigated using an empirical approach. Treatment of the cationic polyenes with nucleophiles gave conversion to neutral compounds, which were characterised by mass spectrometry (MS) and ultraviolet/ visible absorption spectroscopy (UV/Vis), in addition to NMR. In most cases, theidentified neutral compounds supported the structural characterisation of their charged precursors.

The work is of relevance to the classical blue colour reactions of polyenes developed in the early 20th century. The chemistry behind these reactions has previously not been elucidated. Only during the last 15-20 years has the instrumental methods necessary for the study of this chemistry been available.

In current studies on the colouration mechanism of the carotenoproteins present in external tissues of some marine organisms, a polarisation of the polyene chain appear to be of importance. Moreover, radical cations of polyenes are unstable intermediates in Nature, where they are shown to be of importance in photosynthetic processes in green plants and bacteria.

The delocalised polyenylic cations studied here, representing a new direction of structural studies in the carotenoid/retinoid field, are of interest in a wider context for carbocation structure and stability in basic organic chemistry and the various applied aspects outlined above.

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Müller, Wolfram. "Extraction liquide-solide de cations métalliques par des cations amphiphiles." Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20173/document.

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Dans le domaine de la séparation sélective pour le traitement et la valorisation des combustibles nucléaires usés, l'extraction liquide-liquide est largement utilisée au niveau industriel. Cependant dans le cadre des technologies nucléaires du futur, des procédés alternatifs de séparation sont recherchés. Notamment la précipitation sélective d'actinides par des tensioactifs cationiques en milieu aqueux (l'extraction liquide-solide étudié par Heckmann et al dans les années 80) apparaît comme une approche intéressante. Le principal avantage de cette technique, comparée à l'extraction liquide-liquide, est lié à la diminution du nombre d'étapes dans le processus comme le lavage du solvant ou la désextraction des métaux. De plus, c'est une technique sans solvant organique ce qui réduit considérablement la quantité de déchets contaminés. Pour ces travaux de thèse, nous avons utilisé des méthodes physico-chimiques pour mieux comprendre l'interaction spécifique entre le cation métallique et le tensioactif cationique. Nous avons tout d'abord analysé l'effet spécifique des contre-ions anioniques (Cl-, NO3-, C2O42-) provenant des acides utilisés; puis nous avons étudié finement l'introduction de cations alcalins monovalents et quelques cations multivalents sélectionnés (Cu2+, Zn2+, UO22+, Fe3+, Nd3+, Eu3+, Th4+) sur l'auto-assemblage et les propriétés structurels du tensioactif en variant les conditions thermodynamiques. Nous en avons conclu que l'adsorption d'un complexe anionique stable du métal, à l'interface des agrégats micellaires, influence fortement les paramètres d'agrégation du tensioactif et détermine ainsi les limites d'utilisation de cette technique de séparation
In the field of selective separation for recycling of spent nuclear fuel, liquid-liquid extraction processes are widely used (PUREX, DIAMEX …) in industrial scale. In order to guarantee a sustainable nuclear energy for the forthcoming generations, alternative reprocessing techniques are under development. One of them bases on the studies from Heckmann et al in the 80's and consists in selectively precipitating actinides from aqueous waste solutions by cationic surfactants (liquid-solid extraction). This technique has some interesting advantages over liquid-liquid extraction techniques, because several steps are omitted like stripping or solvent washing. Moreover, the amount of waste is decreased considerably, since no contaminated organic solvent is produced. In this thesis, we have carried out a physico-chemical study to understand the specific interactions between the metallic cations with the cationic surfactant. First, we have analysed the specific effect of the different counter-ions (Cl-, NO3-, C2O42-) and then the effect of alkaline cations on the structural properties of the surfactant aggregation in varying thermodynamical conditions. Finally, different multivalent cations (Cu2+, Zn2+, UO22+, Fe3+, Nd3+, Eu3+, Th4+) were considered; we have concluded that depending on the anionic complex of these metals formed in acidic media, we can observe either an adsorption at the micellar interface or not. This adsorption has a large influence of the surfactant aggregation properties and determines the limits of the application in term of ionic strength, temperature and surfactant concentration

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CRESPI, STEFANO. "New Intermediates from Photogenerated Phenyl Cations." Doctoral thesis, Università degli studi di Pavia, 2017. http://hdl.handle.net/11571/1203367.

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La tesi presenta uno studio sulla fotoreattività di composti aromatici volta ad ampliare la classe di substrati in grado di fotogenerare alfa,n-dideidrotolueni a partire da aril cationi nel loro stato di tripletto. Viene riportato inoltre lo studio fotochimico di arilazo mesilati come nuovi prescursori di aril cationi e radicali. In aggiunta viene presentato un approccio fotocatalitico per la generazione di intermedi reattivi svoltosi presso l’Università di Ratisbona. Il lavoro è corredato dallo studio computazionale e meccanicistico sulle reazioni fotochimiche studiate sperimentalmente.
This thesis is devoted to the study of the aromatic compounds photoreactivity and in particular to widen the number of alfa,n didehydrotoluenes precursors from photogenerated triplet aryl cations. The photochemical investigation on arylazo mesylates photoreactivity as novel aryl radicals and cations generators is also presented. Moreover, all reactions experimentally studied are analysed on the basis of computational chemistry.

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5

Robin, Dorothée. "Réactions unimoléculaires des cations ou cations radicaux hétérocycliques et oxygénés en phase gazeuse." Paris 11, 1986. http://www.theses.fr/1986PA112306.

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Ce travail porte sur les mécanismes d’isomérisation et de fragmentation des cations et cations radicaux d’hétérocycles saturés et insaturés en phase gazeuse. Un bref exposé des généralités sur la spectrométrie de masse et sur les mécanismes d’isomérisation des carbocations précède la première partie de ce travail où sont comparés les comportements des ions [M-H]+ provenant des cycles et d’hétérocycles aromatiques. Le comportement des ions alkylfurannes et alkylbenzofurannes protonés est étudiés dans une deuxième partie ainsi que celui d’ions adduits isomères ; Cette étude rend compte de l’existence de processus compétitifs d’isomérisation par transfert 1-2 de méthyle et par des réactions d’agrandissement et de rétrécissement de cycle. Dans une troisième partie, les cations radicaux phtalanne et dihydrobenzofuranne ainsi que leurs homologues supérieurs sont étudiés ; Il a été montré notamment que le cation radical isochromanne se fragmente suivant une réaction de DIELS ALDER et que le cation radical phényloxétanne se réarrange à faible énergie interne en cation radical isochromanne. Les mécanismes de protonation et d’isomérisation du phtalanne, du dihydrobenzofuranne et de leurs homologues supérieurs sont traités dans une quatrième partie. Si les formes protonées du chromanne s’isomérisent entre elles, celles de l’isochromanne ont un comportement autre. Il ressort de l’étude de nombreux isomères que l’allyl phényl éther protoné se réarrange en chromanne protoné puis en ortho propényl phénol protoné.

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6

Nougué, Raphaël. "Silylènes stabilisés par des phosphines : précurseurs de nouveaux cations silyliumylidènes et hétérocycles insaturés." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30021/document.

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Ce travail de thèse est axé sur la réactivité de silylènes stabilisés par un ligand phosphine et notamment leur usage en tant que précurseurs de cations silyliumylidènes (R-Si:+), qui sont des espèces cationiques du silicium avec seulement un substituent et 4 électrons de valences. La stabilisation des silyliumylidènes, espèces hautement réactives, sera envisagée via la coordination des deux bases de Lewis au niveau des deux orbitales vacantes du centre silicié cationique. Le premier chapitre constitue un état de l'art des études portant sur la stabilisation et la réactivité des silylènes. Une emphase particulière a été apportée à la description de leurs propriétés électroniques qui sont responsables de la balance stabilité-réactivité de ces espèces. Le deuxième chapitre présente la réactivité des complexes de silylènes stabilisés par un ligand phosphine dans l'activation réversible des liaisons- E-H (E = R3Si, R2P) via des additions oxydantes/éliminations réductrices. Ce type de réaction est relativement rare pour les complexes non-métalliques mais fréquent avec les complexes de métaux de transition. Le dernier chapitre traite de la synthèse et de la caractérisation d'espèces divalentes cationiques Si(II), les cations silyliumylidènes stabilisés par coordination de deux de ligands L différents comme les phosphines, les sulfures, les pyridines et les carbènes N-hétérocycliques NHC. Parmi les espèces préparées, le cation silyliumylidène stabilisé par une phosphine, de façon intramoléculaire, et le diméthylsulfure, base de Lewis labile, se distingue par une très grande réactivité vis-à-vis de réactifs variées (oléfines, alcynes, silanes,...) conduisant à des cations silylium stabilisés, intramoléculairement, par un ligand phosphine. Ces derniers, restant très réactifs, sont capables de réagir avec un autre substrat. Ces résultats montrent clairement que les silyliumylidènes sont capables d'activer successivement deux molécules différentes, ce qui devrait permettre d'envisager leur utilisation comme des catalyseurs similaires aux complexes de métaux de transition
This thesis focuses on the reactivity of phosphine stabilized silylenes, and particularly their use as precursors of low-coordinate four-valence-electrons silyliumylidene ions (R-Si:+). The stabilization of those highly reactive species will be considered via the coordination of two Lewis bases at the cationic silicon center featuring formally two empty orbitals. In the first chapter an overview concerning the stabilization and reactivity of silylenes is presented. Particular emphasis has been placed on the description of their electronic properties which are responsible for the stability-reactivity balance of these derivatives. The second chapter concerns the use of phosphine-stabilized silylene complexes for the reversible activation of E-H bonds (E = R3Si, R2P) via oxidative addition/reductive elimination processes, which are classical in organometallic chemistry, but rarely observed for main group element species. The last chapter deals with the synthesis and characterization of silyliumylidene ions (R-Si:+), and particularly we have considered their stabilization using a set of two different L ligands such as phosphines, sulfides, pyridines and N-heterocyclic carbenes NHC. Of special interest, the phosphine/dimethylsulfide-stabilized silyliumylidene cation, thanks to the labile sulfide ligand, presents a very high reactivity with various reagents (olefins, alkynes, silanes,...), leading to the formation of the corresponding silylium cations, intramolecularly-stabilized by a phosphine ligand. These latter, remaining very reactive, are able to activate a second type of substrate. These results clearly show that the sililymilydenes are capable of activating successively two different molecules, which should make it possible to envisage their use as catalysts similarly to transition metal complexes

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7

Teasdale, Andrew. "Synthetic ionophores for cations." Thesis, Durham University, 1993. http://etheses.dur.ac.uk/5617/.

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A series of 14-crown-4 derivatives bearing amide substituents have been prepared in order to develop ionophores selective for lithium. Complexation with lithium ions was monitored using ( 13)C and IR spectroscopy and liquid membrane electrodes prepared and evaluated using a fixed interference method. The highest selectivities with respect to sodium ions were obtained for di-n-butylamide-oNPOE and a di-n-benzylamide-oNPOE derivatives; log( POT)(_ Li,Na) = -2.92 and -2.93 respectively. A series of amide and amide-ester N-functionalised coronands based upon [12]-N202 , [15]-N203 and [18]-N204 parent macrocycles has been prepared. Complexation of certain alkali and alkaline-earth cations was monitored by ( 13)C NMR and IR specteoscopy, enthalpies of complexation measured in methanolic solution using micro-calorimetry and stability constants measured in aqueous media by potentiometric methods. Strong complexation of Ca2+ in aqueous media was observed with good selectivity over Na+ and K+. Lower free energies of binding for Ha cations were displayed by the tertiary amide derivative (of [12]N(_2)O(_2)), than by its secondary analogue, despite displaying higher enthalpies of complexation. Thus the lower free energies result from significantly lower entropies of complexation. Two sets of oxa-amide and oxa-ester tripodal ligands have been prepared and solvent membranes fabricated. The effects of the nature of the plasticiser, bis (butylpentyl)adipate (BBPA) verses o -nitrophenyl octyl ether (oNPOE), the ligand structure and the ionic strength of the analyte solution on the electrode response to la and Ila cations were studied. The performance of the oxa-amides was superior to that of the oxa-esters particularly at higher ionic strengths, however super-Nernstian responses were observed with the more charge-dense ions in the presence of chloride and/or with the less polar plasticiser BBPA. Measurements of intracellular sodium concentration could be effected with a sensor based upon bis (N,N',N"-tributyl)-4,4',4"-propylidintris(3-oxabutanamide) and oNPOE for which -log KPOT = 2.64 and -log KPOT =3.0, whilst bis (N,N',N"-tributyl)Na,K Na,Mg-2,2',2"-phenylmethylidintris(3-oxabutamide) and oNPOE functioned as a calcium sensor, displaying excellent selectivity over Mg. -log KPOT= 4.3.Ca,MgAdditionally a triamide based upon a cyclohexane triol skeleton was prepared, a membrane fabricated and its performance assessed as a sodium sensor.

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8

Robin, Dorothée. "Réactions unimoléculaires des cations ou cations radicaux hétérocycliques et oxygènes en phase gazeuse." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb37600792s.

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9

Fauvelle, Florence. "Décontamination des cations toxiques : la voie des cyclodextrines." Université Joseph Fourier (Grenoble), 1999. http://www.theses.fr/1999GRE19003.

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10

Depauw, Alexis. "Synthèse et étude photophysique de sondes fluorescentes pour la détection de cations alcalins en milieux aqueux." Thesis, Cachan, Ecole normale supérieure, 2014. http://www.theses.fr/2014DENS0040/document.

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L’objet de cette thèse a été la réalisation de sondes moléculaires fluorescentes pour de la détection de césium et de potassium en milieu aqueux. Deux problématiques ont été abordées : la détection de traces de césium en vue d’applications environnementales, et la mesure de variations de potassium en milieu biologique en vue d’applications biologiques. La première partie de cette thèse concerne la détection du césium. Dans un premier temps, différentes entités complexantes du césium ont été étudiées dans le but de mesurer des concentrations de césium comprises entre 1.10-3 et 5 ppm. Certaines de ces sondes ont ensuite été utilisées au sein d’un système de mesures basé sur un circuit micro-fluidique destiné à mesurer le césium de façon continue. La seconde partie de cette thèse s’intéresse à la détection du potassium. Dont le but a été de mettre au point des sondes pour mesurer le potassium extracellulaire par imagerie de fluorescence. Une cage complexante sélective du potassium a tout d’abord été identifiée. Différentes stratégies ont ensuite été développées pour remplacer la coumarine par un fluorophore excitable à de plus hautes longueurs d’ondes. Parmi les sondes étudiées, le Calix-COU-Alcyne-Sulf a permis d’effectuer des mesures in vitro préliminaires qui ont montré que ce type de sondes ne perturbe pas l’activité neuronale et permet de détecter le potassium dans la gamme de concentration visée
The aim of this PhD was to study fluorescent molecular sensors in order to detect cesium and potassium in aqueous media. Two different issues have been addressed: the detection of cesium traces for environmental applications, and the measure of potassium fluctuations for biological applications. The first part concerns the detection of cesium. Several complexing units were first studied, to measure cesium concentration between 1.10-3 and 5 ppm. Some of the molecules made were then used in a measuring system based on a micro-fluidic chip to measure cesium in a continuous way. The second part concerns the detection of potassium. The aim was to design sensors to measure extracellular potassium fluctuations by fluorescence imaging. A selective complexing unit was first found. Several strategies were then explored to replace a coumarin by a fluorophore excitable at higher wavelengths. Among the molecules made, the Calix-COU-Alcyne-Sulf enabled preliminary in vitro measurements and showed that this type of molecules does not affect the neuronal activity and enables to measure potassium in the range of concentration targeted

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11

Gao, Shuang [Verfasser], Meike [Akademischer Betreuer] Niggemann, and Markus [Akademischer Betreuer] Albrecht. "Study of reactive intermediates: vinyl cations and aminium radical cations / Shuang Gao ; Meike Niggemann, Markus Albrecht." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1181109159/34.

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12

Rideout, Jan. "Selected radical cations : an E.S.R. study." Thesis, University of Leicester, 1986. http://hdl.handle.net/2381/33870.

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This thesis is concerned with a process which has become commonly used. Producing radical cations specifically for observation at reduced temperatures within the X-band electron spin resonance spectrometer cavity. Gamma irradiation is used to cause electron addition and electron loss centres in a CCl3F matrix. These damage centres can be passed to solutes by the processes outlined below:- [equation] Various functional groups have been investigated. A variety of groups have been chosen to attempt to show a great many of the effects, which cause a molecule to produce interesting e.s.r. spectra. Effects ranging from the 'solvent adducts' investigated in Chapter 2, to the Breit-Rabi distortions encountered by the cations of dialkyl mercurials. Attempts have also been made to clarify one or two areas of radical cation chemistry which have caused contention in the current literature. Such areas are those outlined in Chapters 3, 4 and 5 with ester groupings and Chapter 7 with oxirane cations.

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13

King, Angela Marie. "Chromogenic reagents for amines and cations." Thesis, University of Liverpool, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317009.

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Kaleem, Z. "Gas phase reactions of amide cations." Thesis, University of Essex, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382525.

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15

Fernandes, Anthony. "Etude et réactivité des cations silyliums." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0255.

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Cette thèse a pour but d’étudier et d’approfondir les connaissances actuelles dans le domaine de la chimie des silyliums. Ces espèces cationiques semblables aux carbocations sont dotées d’une forte réactivité même vis-à-vis d’espèces très peu nucléophiles, ce qui leur confère des propriétés remarquables en tant qu’acide de Lewis. Les objectifs de cette thèse relèvent d’une tentative de dompter cette grande réactivité, via des méthodes de stabilisation du silylium, en conservant un bon compromis réactivité/stabilité. Un second axe de recherche envisagé est a visé d’application de ces silyliums en catalyse asymétrique et pour cela différents modèles ont été étudiés. Pour cela, l'introduction d'une chiralité centrée sur le silicium ou l'utilisation d'anion chiraux ont été étudiés
The main objective of this thesis was to develop a better understanding of the silylium chemistry. These cationic three-coordinate silicon species similar to carbeniums are extremely reactive against any nucleophile and the extraordinarily high avidity of these cationic species for electron density make them remarkable Lewis acids. In this context, our aim during this thesis was to tame the reactivity of silyliums by means of introducing stabilisation at the cationic silicon center while preserving most of its reactivity. The study of new systems may provide informations on the way to find the best reactivity/stability compromise. Another part of this work was to focus on chirality in this stabilized silyliums to allow future asymmetric catalysis applications and the introduction of silicon-centered chirality but also chiral anions were probed

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16

Fletcher, James. "Studies of atomic and molecular cations." Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1420899/.

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Atomic and molecular cations have the potential to strongly influence a number of industrial, atmospheric and interstellar environments in which they are expected to be present. As a result, information on the generation and reactivity of positively charged species is invaluable when attempting to model and understand the physical and chemical processes taking place in such surroundings. This thesis reports a number of experimental investigations of the formation and reactivity of atomic and molecular cations. Firstly, a detailed study of the electron ionisation of sulphur dioxide (SO2) is presented. Relative precursor-specific partial ionisation cross sections for the fragment ions formed following electron ionisation of sulphur dioxide have been measured using time-of-flight mass spectrometry coupled with ion coincidence detection. These data quantify, for the first time, the formation of all fragment ions, relative to the formation of SO2+, via single, double and triple electron ionization of SO2. Secondly, the investigations of the bimolecular reactivity of a number of doubly (I2+ and N22+) and triply charged (I3+, Xe3+, CS23+) reactants are presented. A crossed-beam mass spectrometer was used to identify ion-molecule reaction products. The doubly and triply charged (I2+ and I3+/Xe3+) reactants are shown to participate in processes involving substantial rearrangement of chemical bonds. This reactivity can be encapsulated using a simple electrostatic model and energetic arguments. Furthermore, the same model has been updated to account for the results observed following the reactions of atomic trications. A different mass spectrometer, equipped with a position-sensitive coincidence ion detector, was then used to explore the dynamics of reactions involving first a molecular dication (N22+) with various low-mass organic molecules and then atomic (Xe3+) and molecular trications (CS23+). Product ion velocities determined using this technique can be used to explore the reaction energetics and angular scattering distributions for individual ion-molecule reaction channels. In turn, the interpretation of these data allow the identification of reaction mechanisms. The range of reactions exhibited in all of these studies is surprisingly diverse, clearly indicating a complex chemistry for collision systems involving dicationic and tricationic reactants.

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17

Armstrong, Roland. "Catalytic asymmetric reactions employing chiral cations." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:6f38eb98-32ff-4b06-b144-100480da87dd.

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This thesis describes two new phase-transfer catalysed processes, in which asymmetry is mediated via ion-pairing with a chiral cation. In the first chapter, an enantioselective method for N functionalization of pyrroles is described and a phase-transfer catalysed approach to axial chirality via a cation-directed SNAr reaction is discussed in Chapters 3, 4 and 5.

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18

Park, Chul. "Cations and activated sludge floc structure." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/34253.

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This research was designed to investigate the effect of cations on activated sludge characteristics and also to determine their influence on digestion performance. For this purpose, cations in solution and in floc were evaluated along with various activated sludge characteristics and the collected waste activated sludge underwent both anaerobic and aerobic digestion. It was found that large amounts of biopolymer (protein + polysaccharide) remained in the effluent of WWTP that received high influent sodium but had low iron and aluminum in floc. However, sludges from plants with high sodium and high iron and aluminum dewatered well and produced high quality effluents, suggesting that iron and aluminum have significant positive effects on floc properties. Following anaerobic digestion, a significant increase in solution protein occurred and correlations between solution protein, ammonium production, percentile volatile solids reduction and iron in floc were obtained. These data indicate that iron-linked protein is released to solution when iron is reduced and its degradation is responsible for volatile solids reduction in anaerobic digestion. In aerobic digestion, polysaccharide in solution increased along with calcium, magnesium and inorganic nitrogen. This implies that divalent cation-bound biopolymer might be the primary organic fraction that is degraded under aerobic digestion. Combined (anaerobic/aerobic) digestion was performed and produced further volatile solids destruction with discrete cation and biopolymer response during each phase of digestion. These results support the theory that two types of organic matter with different cation bindings are present in floc and each type is degraded under different digestion processes.
Master of Science

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19

Wang, Yonghui. "The Chemistry of Cyclopropylarene Radical Cations." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/29818.

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Cyclopropane derivatives are frequently utilized as "probes" for radical cation intermediates in a number of important chemical and biochemical oxidation. The implicit assumption in such studies is that if a radical cation is produced, it will undergo ring opening. Through a detailed examination of follow-up chemistry of electrochemically and chemically generated cyclopropylarene radical cations, we have shown that the assumption made in the use of these substrates as SET probes is not necessarily valid. While cyclopropylbenzene radical cation undergoes rapid methanol-induced ring opening (e.g., k = 8.9 E7 s-1M-1), the radical cations generated from 9-cyclopropylanthracenes do not undergo cyclopropane ring opening at all. The radical cations generated from cyclopropylnaphthalenes disproportionate or dimerize before undergoing ring opening. Utilizing cyclic, derivative cyclic, and linear sweep voltammetry, it was discovered that decay of radical cations generated from cyclopropylnaphthalenes in CH3CN/CH3OH is second order in radical cation and zero order in methanol. Anodic and Ce(IV) oxidation of all these naphthyl substrates in CH3CN/CH3OH led to cyclopropane ring-opened products. However, the rate constant for methanol-induced ring opening (Ar-c-C3H5+. + CH3OH -> ArCH(.)CH2CH2O(H+)CH3) is extremely small for 1-cyclopropylnaphthalenes) despite the fact that ring opening is exothermic by nearly 30 kcal/mol. These results are explained on the basis of a product-like transition state for ring opening wherein the positive charge is localized on the cyclopropyl group, and thus unable to benefit from potential stabilization offered by the aromatic ring. Reactions of radical cations generated from 9-cyclopropylanthracenes in CH3CN/CH3CN have also been investigated electrochemically. The major products arising from oxidation of these anthryl substrates are attributable to CH3OH attack at the aromatic ring rather than CH3OH-induced cyclopropane ring opening. Ce(IV) oxidation of 9-cyclopropyl-10-methylanthracene and 9,10-dimethylanthracene further showed that radical cations generated from these anthryl substrates undergo neither cyclopropane ring opening nor deprotonation but nucleophilic addition. Side-chain oxidation products from Ce(IV) oxidation of methylated anthracenes arose from further reaction of nuclear oxidation products under acidic and higher temperature conditions. An analogous (more product-like) transition state picture can be applied for cyclopropane ring opening and deprotonation of these anthryl radical cations. Because of much higher intrinsic barrier to either nucleophile-induced cyclopropane ring opening or deprotonation of these anthryl radical cations, nucleophilic addition predominates. Stereoelectronic effects may be another additional factor contributing to this intrinsic barrier because the cyclopropyl group in these anthryl systems adopts a perpendicular conformation which may not meet the stereoelectronic requirements for cyclopropyl ring opening at either the radical cation or dication stage.
Ph. D.

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Huang, Fu-shiuan. "Photodissociation of gas phase organic cations." Case Western Reserve University School of Graduate Studies / OhioLINK, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=case1055788814.

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21

West, H. K. "Competing divalent cations in biological systems." Thesis, University of Worcester, 2001. http://eprints.worc.ac.uk/7188/.

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22

Benco, John S. "The rational design and synthesis of ionophores and fluoroionophores for the selective detection of monovalent cations." Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-0410103-125803/.

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23

Karam, Omar. "Nouvelles voies d'accès aux 4-halogénocyclohexa-2,5-diénones par chloration et fluoration de dérivés phénoliques para-substitués : application à la synthèse d'hétérocycles oxygénés ou azotés." Poitiers, 1994. http://www.theses.fr/1994POIT2299.

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Les 4-halogenocyclohexa-2,5-dienones qui donnent lieu au rearrangement dienone-phenol et constituent des intermediaires pour la synthese de molecules complexes presentent un interet tout particulier. Nous rapportons des methodes nouvelles et generales de synthese de 4-chloro et 4-fluorocyclohexa-2,5-dienones. La chloration electrophile de derives phenoliques par association d'un acide de lewis (pentafluorure (ou pentachlorure) d'antimoine) et d'un chloromethane, permet d'acceder aux 4-chlorocyclohexa-2,5-dienones. Ces memes dienones sont obtenues par une chloration nucleophile des ethers de phenols par un iode polyvalent en presence d'ion chlorure. De facon analogue, la fluoration nucleophile des phenols eux memes par le bis (trifluoroacetoxy) iodobenzene en presence d'ion fluorure conduit exclusivement aux 4-fluorocyclohexa-2,5-dienones. L'application de ces reactions aux derives phenoliques portant un substituant oxygene ou azote a permis la synthese de composes bicycliques polyfonctionnels. En conclusion les nouvelles reactions decrites constituent une preparation efficace des 4-halogenocyclohexa-2,5-dienones et d'enones heterocycliques precurseurs de molecules plus elaborees

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24

Schlientz, Nathan William. "Charge Migration through Duplex DNA: A Study of the Mechanism for Charge Migration and Oxidative Damage." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-05182006-164757/.

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Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2007.
Laren M. Tolbert, Committee Member ; Uzi Landman, Committee Member ; Nicholas V. Hud, Committee Member ; David M. Collard, Committee Member ; Gary B. Schuster, Committee Chair.

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25

HARRATA, ABDELKAMEL. "Reactivite en phase gazeuse de cations radicaux : ceto-esters et dioxolannes-esters et de cations acylium substitues." Paris 6, 1989. http://www.theses.fr/1989PA066708.

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La reactivite d'ions bifonctionnels de faible energie interne: des ceto-esters ionises ch#3co(ch#2)#nco#2ch#3, de ions acylium ch#3co(ch#2)#nco#+ et co(ch#2)#nco#2ch#3#+ n=2 a 5; du methyl-2 dioxolanne-2 propanoate de methyle ionise est etudiee en phase gazeuse a l'aide des techniques de spectrometrie de masse. L'interpretation du comportement de ces ions (fragmentations precedees ou non d'isomerisations) s'appuie sur: l'analyse des decompositions unimoleculaires et bimoleculaires d'ions dont la duree de vie est de l'ordre de 10##5 s et l'utilisation de composes marques aux isotopes stables (deuterium, oxygene dix huit, carbone treize). Les resultats les plus significatifs sont les suivants: 1) les ceto-esters ionises se fragmentent essentiellement par ruptures homolytiques de differentes liaisons en et des groupes fonctionnels; 2) les ions acylium co(ch#2)#nco#2ch#3#+ s'isomerisent avant fragmentation par transfert 1, n+2 du groupe methoxyle rendant les deux fonctions carbonyles equivalentes; 3) les ions acylium ch#3co(ch#2)#nco#+ s'isomerisent avant fragmentation en ions (m-1)#+ de lactones ce qui a pour consequence de rendre indiscernable les deux atomes d'oxygene

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26

PROVOT, GERARD. "Complexes ion-neutre : especes intermediaires dans le decompositions de cations radicaux et cations organiques en phase gazeuse." Paris 6, 1993. http://www.theses.fr/1993PA066214.

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Cette these expose une etude fondamentale de la dissociation unimoleculaire de l'acetamide ionise et de plusieurs de ses isomeres, et de cations comme le suboxyde de carbone protone ou des ions issus de la fragmentation de cetoamides. Les donnees experimentales sont issues de l'analyse fine des spectres des ions metastables et de collisions (mike, mike-cid) ainsi que les spectres de neutralisation-reionisation (nrms). La structure et la thermochimie des ions sont egalement abordees par des calculs d'orbitales moleculaires semi-empiriques (methode am1) et ab initio. L'introduction de la correlation electronique a ete demontree comme obligatoire pour le calcul des complexes ion-neutres qui sont la base de ce travail. Le chapitre 1 traite de ces outils experimentaux et theoriques de maniere tres pedagogique. Les quatre autres chapitres sont consacres a l'etude proprement dite. Les faits experimentaux sont analyses et compares aux resultats theoriques. L'accent est mis sur l'interet de la modelisation des mecanismes de fragmentation, mais aussi sur ces limitations. La description des complexes ion-neutre fait l'objet d'une nouvelle approche empirique qui permet de predire les types de complexe possible pour un systeme donne. La validite de cette regle est demontree dans le traitement des cas etudies experimentalement et par l'analyse critique d'exemples voisins issus de la litterature. Enfin, l'utilisation de la nrms a permis de mettre en evidence que le radical genere par neutralisation du suboxyde de carbone protone est stable. L'accent est mis sur l'utilisation des calculs d'orbitale moleculaire pour predire l'observation de l'ion parent dans un spectre de nrms

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27

Ripoche, Xavier. "Ionisation et dissociation multiphotonique resonnante appliquees a la spectroscopie de cations polyatomiques-spectroscopie vibronique du cation chlorobenzene." Paris 11, 1990. http://www.theses.fr/1990PA112221.

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Une nouvelle technique de spectroscopie d'ions polyatomiques est presentee. Son principe repose sur la dissociation multiphotonique resonnante (dmpr) des ions. La detection des fragments ioniques permet la mesure des etats vibroniques. Les etats non radiatifs peuvent etre etudies par cette methode, ce qui n'est pas possible avec les techniques spectroscopiques reposant sur la detection des photons. Les etats electroniques des systemes polyatomiques ioniques etant dans la plupart des cas non radiatifs. Ces dernieres techniques sont bien souvent inutilisables. Le principe de la methode est le suivant: les ions sont formes avec un premier laser par ionisation multiphotonique resonnante (impr) dans un spectrometre de masse a temps de vol. Avec un deuxieme laser de longueur d'onde variable, les ions sont fragmentes par dissociation multiphotonique resonnante a deux photons. Le premier photon est resonnant avec la transition vibronique a mesurer et le second apporte l'energie suffisante a la dissociation. La mesure du rendement d'ions fragments en fonction de la longueur d'onde du deuxieme laser reflete la spectroscopie de premiere la transition resonnante. Nous avons illustre la technique dmpr-impr par l'etude de la spectroscopie vibronique du cation chlorobenzene

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28

Moradi, Alfred. "Organic synthesis via anodically generated iminium cations." Thesis, Queen Mary, University of London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297194.

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29

Pecheux, Muriel. "Cyclisation reactions mediated by sulfur-stabilised cations." Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.481499.

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30

Sohal, Wazir Singh. "The synthesis of chemistry of organosilicon cations." Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.405220.

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31

Vieuxmaire, Olivier P. J. "Photodissociation dynamics of interhalogen molecules and cations." Thesis, University of Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427909.

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32

Faria, Cristiano Gomes de. "Adsorção de cations metalicos sobre silica organofuncionalizada." [s.n.], 1996. http://repositorio.unicamp.br/jspui/handle/REPOSIP/250626.

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Orientador: Jose de Alencar Simoni
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica
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Mestrado

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33

Obaid, Yassin Najim. "Mobilité des cations alacalins dans les matériaux." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb37600117c.

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34

Beres, Joanna M. "Reactions of Silanes and Chlorophosphazenes with HMPA." University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1311620295.

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35

Lam, Ngor-wai. "Generation and characterization of cationic and anionic radical peptides." Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B37097672.

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36

Gerlicher, Ansgar Robert Sandy. "Developing collaborative XML editing systems." Thesis, University of the Arts London, 2007. http://ualresearchonline.arts.ac.uk/5372/.

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In many areas the eXtensible Mark-up Language (XML) is becoming the standard exchange and data format. More and more applications not only support XML as an exchange format but also use it as their data model or default file format for graphic, text and database (such as spreadsheet) applications. Computer Supported Cooperative Work is an interdisciplinary field of research dealing with group work, cooperation and their supporting information and communication technologies. One part of it is Real-Time Collaborative Editing, which investigates the design of systems which allow several persons to work simultaneously in real-time on the same document, without the risk of inconsistencies. Existing collaborative editing research applications specialize in one or at best, only a small number of document types; for example graphic, text or spreadsheet documents. This research investigates the development of a software framework which allows collaborative editing of any XML document type in real-time. This presents a more versatile solution to the problems of real-time collaborative editing. This research contributes a new software framework model which will assist software engineers in the development of new collaborative XML editing applications. The devised framework is flexible in the sense that it is easily adaptable to different workflow requirements covering concurrency control, awareness mechanisms and optional locking of document parts. Additionally this thesis contributes a new framework integration strategy that enables enhancements of existing single-user editing applications with real-time collaborative editing features without changing their source code.

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37

Auboiroux, Michel. "Affinité de différents cations métalliques (Co2+, Ni2+, Cu2+, Zn2+, Cd2+ et Pb2+) pour une montmorillonite calcique : expérimentation et applications." Orléans, 1998. http://www.theses.fr/1998ORLE2025.

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L'etude experimentale des interactions entre metaux lourds (co, ni, cu, zn, cd, pb) et une montmorillonite purifiee calcique est menee en considerant differentes conditions experimentales (force ionique moderee ou elevee, argile en suspension ou compactee). L'argile et les solutions utilisees sont prealablement caracterisees. Le mecanisme d'echange ionique est mis en evidence par analyse quantitative xps d'echantillons echanges avec cd et pb. Le traitement des resultats experimentaux obtenus en solutions de force ionique moderee et constante, par un modele d'echange ionique et sa fonction puissance permettent de retracer la repartition entre especes adsorbees et especes dissoutes, sur le code de calcul phreeqc. La theorie hsab (hard and soft acid and base) permet de quantifier la sequence de selectivite observee experimentalement pour cu, zn, cd et pb en reliant les proprietes de surface de l'argile a l'electronegativite et la softness des metaux. Une discussion est proposee concernant le role joue par l'heterogeneite energetique des surfaces basales de l'argile et l'hydratation des cations sur la selectivite. Des experiences en solutions de force ionique 3m, montrent l'adsorption anionique de zn et pb (essentiellement presents sous forme m(cl 4) 2 -) mettant en evidence le role preponderant de la speciation des metaux (determinee par le modele de pitzer) sur leurs interactions avec l'argile. Le reste de ce travail est consacre a deux applications de l'echange ionique : _ les performances hydrodynamiques et chimiques d'un geosynthetique bentonitique (gsb) et d'une couche d'argile dans un dispositif d'etancheite de fond de decharge, sont comparees par simulation. Compte tenu de leur faible epaisseur, les gsb ne peuvent pas etre consideres comme equivalents a une couche d'argile compactee ; _ l'utilisation d'argiles comme depolluants est envisagee par des experiences portant sur des effluents industriels reels. La calcination des argiles permet l'inertage des metaux.

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38

Kamiya, Takehiro, and Masayoshi Maeshima. "Residues in Internal Repeats of the Rice Cation/H+ Exchanger are Involved in the Transport and Selection of Cations." the American Society for Biochemistry and Molecular Biology, 2004. http://hdl.handle.net/2237/7088.

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39

Aksenov, Alexander A. "Gas phase structure and reactivity of zirconocene cations." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0012946.

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40

Kwan, Daniel Cheuk Hang. "Modulation of Kv1.5 slow inactivation by external cations." Thesis, University of British Columbia, 2006. http://hdl.handle.net/2429/31088.

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Slow inactivation is an intrinsic biophysical property of voltage-gated potassium (Kv) channels that results in a non-conducting state under physiological conditions. It limits the amount of current through Kv channels and affects cellular excitability. However, the molecular basis of slow inactivation is not well understood. In this thesis investigation, the modulation of slow inactivation in the human Kvl .5 channel by extracellular Zn²⁺, protons (H⁺), Ni²⁺, and other divalent-cations was studied using standard voltage clamp techniques. Zn²⁺, H⁺, and Ni²⁺ accelerated slow inactivation and caused a current inhibition in Kvl.5 expressed in HEK-293 and mouse ltk cells. The current inhibition was hypothesized to result from the binding of Zn²⁺, H⁺, and Ni²⁺ to the turret histidine residue (H463) which in turn promoted a slow inactivation process involving the outer pore mouth arginine residue (R487). The current inhibition induced by Zn²⁺, H⁺, and Ni²⁺ was attenuated either by increasing extracellular [K⁺] or by mutating H463 to glutamine (H463Q) or R487 to valine (R487V). Unitary current analysis revealed H⁺ and Ni²⁺ did not change the single channel current at +100 mV or the single channel conductance between 0 and +100 mV, but the number of blank (null) sweeps recorded with depolarizing pulses lasting up to 1 s was increased. The proportion of null sweeps correlated well with the extent of inhibition of macroscopic Kvl .5 current by external H⁺. A model incorporating two modes of gating was employed to describe the transitions between the active sweeps (mode A) and the null sweeps (mode U), and external H⁺ was proposed to inhibit Kv 1.5 current by promoting mode U gating. Consistent with this model was the finding that external K⁺ antagonized mode U gating induced by external H⁺. Channels were observed to switch from mode U back to mode A during prolonged depolarizations (> 6 s), and the delay in opening (first latency) was correlated with the dwell time in a depolarization-induced slow inactivated state. Together, the results suggest that Zn²⁺, H⁺, and Ni²⁺ inhibit Kvl .5 current by promoting a slow (P/C- type) inactivation process proceeding from closed states.
Medicine, Faculty of
Cellular and Physiological Sciences, Department of
Graduate

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41

Webb, Alexander. "Imaging the photodissociation dynamics of molecular hydride cations." Thesis, University of Bristol, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492462.

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The work presented in this thesis constitutes an imaging study of the photodissociation of state-selected molecular cations, each of which was prepared by (2+1) resonance-enhanced multiphoton ionisation (REMPI).

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42

Kendrick, Aidan Gerard. "Synthetic and structural studies of some thiazene cations." Thesis, Durham University, 1986. http://etheses.dur.ac.uk/7085/.

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S(_5)N(_5)Cl has been produced by a new route and is much more stable than previously reported owing to greater purity. Its chemical reduction to (SN) and reactions with SO and BF were studied. An X-ray structure analysis (R.W.H. Small) revealed secondary cation-anion interactions; the resulting strain in the cation ring could be detected both by bond angle-bond length correlations and MNDO calculations. Electro-reduction of S(_5)N(_5)Cl in liquid SO(_2) produced finely powdered (SN)(_x) which could be used to form good quality vapour deposited films. Cyclic voltammograms in liquid SO(_2) (obtained after spending much time developing an improved procedure) indicated possible solvent participation in the reduction process and so electrocystallization of (SN) by electro-reduction of S(_5)N(_5)BF(_4) (prepared from S(_5)N(_5)Cl) in acetonitrile was investigated. Cyclic voltammetric evidence was used to propose a mechanism of reduction and bulk electrolyis experiments using bright platinum and (SN)(_x) film cathodes showed the influence of the cathode on the nature of the (SN)(_x) deposit. Small quantities of NSF were produced in ca. 80% yield by the solid state reaction of SN(^+)AsF(_6)ֿ and excess CsF; an unoptimised larger scale preparation indicated the usefulness of this route. Various gas phase reactions of NSF were studied using infrared spectroscopy. Attempts to prepare the simple fluoride S(_4)N(_3)F by metathesis from S(_4)N(_3)BF(_4) and CsF were only partially successful owing to reaction with solvent. Reaction of S(_3)N(_2)(^2+)(AsF(_6)ֿ)(_2) with CsF (1:1) produced S(_3)N(_2)F(^+)AsFֿ but further conversion to S(_3)N(_2)F(^2) was not possible owing to reaction with solvent. Attempted crystal growth experiments indicated that the S(_3)N(_2)(^2+) ion existed in an equilibrium mixture containing S(_2)N(^+) and SN(^+) ; this hypothesis was confirmed by its reactions with sulphur and hexafluorobut-2-yne. These solution equilibria were exploited by designing more convenient preparations of S(_3)N(_2)(^2+) (AsF(_6)ֿ)(_2) and S(_2)N(^+)SbCl(_6)ֿ . The chemical reactions of SN(^+)AsF(_6)ֿ were studied with a view to the preparation of new compounds. Although no such species were isolated, the results usefully indicated future experiments and the oxidising properties of the SN(^+) cation.

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43

Sandanayake, Kaththota Ralalage Arunasiri S. "Fluorescent macrocyclic sensors for alkali and other cations." Thesis, Queen's University Belfast, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356861.

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44

Forfar, Laura C. "Coordination and reactivity of post d 10 cations." Thesis, University of Bristol, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.652037.

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This thesis investigates the formation and subsequent coordination and reactivity of post d 10 metal cations, specifically cations of the group 11 metals and group 15 and 16 compounds. Cation formation is facilitated by abstraction of a chloride from the starting compound by Lewis acidic gallium trichloride or by exchange of the chloride by reaction with silver hexafluoroantimonate. Simple metal salts, MX (M = Cu, Au, X = Cl, M = Ag, X = OTt) were reacted with GaCl), generating cations in situ, and addition of P 4 yielded three new M -P 4 complexes. Copper and silver formed coordination polymers, whereas gold reacted to form a homoleptic cation, [Au(rrP4)2][GaCI4], in the first example of a white phosphorus complex of gold. The gold complex was particularly sensitive to air and moisture and thus stabilised cations were generated by the abstraction of a halide from ligated copper and gold complexes to further probe the M-P4 interaction. The coordination of white phosphorus yielded complexes of the type [LM(rrp4)][X] and the solid-state structures, characterised by X-ray crystallography, showed P 4 coordinated in 112- fashion in all instances. All the complexes showed the P 4 unit to be fluxional in solution, with the room temperature 3lpeH} NMR spectra showing broad peaks. At low temperatures, the fluxionality within the gold complexes was slowed on the NMR timescale and the peaks resolved into 2nd order splitting patterns. The dynamic behaviour of the P 4 unit coordinated to [LAu t was investigated computationally which revealed a dynamic pathway via a 11 1- transition state. The reactivities of the complexes were tested through a variety of experiments.

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45

Amorim, Efigenia. "Adsorção de tensoativos em resina trocadora de cations." [s.n.], 1995. http://repositorio.unicamp.br/jspui/handle/REPOSIP/250333.

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Orientadores: Fernando Galembeck, Mauricio Urban Kleinke
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
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Doutorado

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46

Silalahi, Imelda. "Photochemical activation of tetraalkylammonium cations by hexachloroplatinate(IV)." Thesis, University of York, 2017. http://etheses.whiterose.ac.uk/17514/.

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Unexpectedly, a Zeise’s salt analogue, the dinuclear, butadiene-bridged complex, trans-eta^2:eta^2-1,3-butadiene-bis(trichloroplatinate(II)) was isolated when [AuCl4] and [PtCl4]2- were reacted together in the presence of the tetrabutylammonium cation. Early observations ruled out the involvement of the gold(III) species in generating the butadiene directly, but it was found to be acting as an oxidising agent facilitating conversion of [PtIICl4]2- to [PtIVCl6]2-, which turned out to be a key observation. Further studies identified the source of the C4 fragment of butadiene as the tetrabutylammonium cation, suggesting a C-H activation, perhaps via some Shilov chemistry, linked perhaps to a Hofmann-like elimination. The reaction is photochemical and proceeds directly from (NBu4)2[PtCl6] in the total absence of gold. A computational study and related literature precedent regarding the excited state of [PtCl6]2- showed the formation of PtIII as well as chlorine radicals, revealing the possibility for radical induction of the reaction. Indeed, PtIII and N-based radicals were found in the electron paramagnetic spectroscopy (EPR) spectrum of an irradiated frozen solution. Given the extrusion of a butadiene fragment from the tetrabutylammonium cation, the possible involvement of Hofmann elimination mechanism was considered. One possibility would be the elimination of butene in the first step with concomitant reduction to PtII leading to a butene analogues of Zeise’s salt, which could then react further to give the observed product. However, this possibility was not supported by the observed unreactivity of [PtCl3(butene)]- (butene = 1-butene or 2-butene) under the prevailing reaction conditions. This led to the proposal of an intermediate complex in which (Bu3N(butene))+ is pi-bound to [PtCl3]-, which was supported by mass spectrometric evidence from a photochemical study. The same reaction was carried out with the [PtCl6]2- salt of other tetraalkylammonium cations (NPr4+ and NPe4+) and alkene-PtII complexes were again found with NPe4+ salts but not with NPr4+ salts. All of these results and observation were collected together to propose an outline mechanism for the reaction. In a totally separate piece of work, some examples of polycatenar 2,5-diphenylpyridine ligands (LH) were prepared and bound to palladium(II) to give complexes with an orthometallated 2-phenylpyridine and an acac co-ligand - [Pd(L)(acac)]. These are analogous to related PtII complexes prepared in the group which were found to be liquid-crystalline and emissive. While some liquid-crystalline examples were prepared, none of the complexes showed evidence for room-temperature triplet emission, which can be a feature of palladium congeners. However, in the related platinum chemistry it was observed that on formation of the complexes with three alkyloxy groups on the metallating phenyl ring, there was a Pt-promoted C-O bond cleavage. The milder conditions required for formation of the palladium meant that the same C-O bond cleavage was not observed here.

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47

Segall, Martha. "The effects of cations on activated sludge characteristics." Thesis, Virginia Tech, 1987. http://hdl.handle.net/10919/45911.

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This research was prompted by a field study performed at the Celanese Corporation Wastewater Treatment Plant, Narrows, VA., in which calcium chloride addition had improved sludge characteristics that were believed to have deteriorated because of sodium hydroxide additions for pH control.

Research objectives were to determine whether the observed improvements during the full-scale plant study were caused by the addition of divalent cations and whether the deterioration of the sludge was due to sodium ion additions.

Bench-scale, activated sludge reactors were fed wastewater from the Celanese plant to model plant conditions. Sodium was added in an attempt to cause deterioration of the sludge characteristics. Magnesium and calcium were used as divalent cations to try to improve the sludge characteristics.

Results of the study indicated that the magnitude of the effects seen in the full-scale plant study could not be reproduced in the laboratory. Magnesium produced little or no effect on the system and calcium improved the sludge characteristics slightly. Sodium caused deterioration of the sludge but not as dramatically as the full-scale study. This suggested that sodium alone did not adversely affect the sludge but rather, sodium hydroxide might have been combined with organics in the waste which then affected the system.

Master of Science

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48

Yeh, Kuei-Jyum. "The influence of cations on activated sludge behavior." Thesis, Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/54375.

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This study investigated the influence of cations on biopolymer characteristics and sludge properties. Settling and dewatering properties of sludges were measured and correlated to the biopolymer characteristics. In addition, effects of cations on sludge conditioning with polymer were studied. Experiment mainly consisted of two parts, reactor study and batch study. In re- actor study continuous-flow reactors were operated. Variables used included varying types of substrate, addition of magnesium or sodium, and changes in pH. The batch study included conditioning tests on the sludges with combinations of cationic polymer and salts. Biopolymers were extracted using alkali extraction followed by gel filtration and subsequent carbohydrate and protein analysis. The sludge settling and dewatering were measured in terms of SVI and specific resistance, respectively. Sludge filtering rate (TIF) was used to measure the conditioning efficiency. The results indicated that the influence of cations depended on the type and concentration of salt. An optimal concentration of Mg was found to improve biopolymer binding. The organic composition of feed also affected biopolymer characteristics. A higher pH combined with a high amount of sodium released biopolymer and resulted in sludge deflocculation. A relationship between unbound biopolymer and soluble effluent COD was observed but no discernible relation between biopolymer binding and sludge settling and dewatering properties was found. Cations were found to reduce polymer requirement during sludge conditioning. In addition, the amount of extractable biopolymers by alkali extraction was greatly influenced by salt. Magnesium inhibited the release of biopolymer, but sodium im- proved the efficiency of biopolymer extraction.
Master of Science

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49

LE, BLANC ALAIN. "Reactions unimoleculaires en phase gazeuse, de radicaux cations bifonctionnels : beta ceto-alcool, beta ceto-esters et de cations beta ceto-acylium." Paris 6, 1988. http://www.theses.fr/1988PA066349.

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Une introduction generale sur la spectrometrie de masse precede une premiere partie portant sur l'interpretation des fragmentations de la dimethyl-3,3 hydroxy-4 butanone-2 a basse energie. Une seconde partie est reservee aux fragmentations de plusieurs beta ceto-esters diversement substitues. Dans une troisieme partie sont examinees les decompositions unimoleculaires d'ions acylium beta carbonyles de faible energie interne. L'accent est mis, tout au long de ce travail, sur le role essentiel des atomes d'oxygene dont la presence induit des ruptures caracteristiques mais aussi sert de relais aux transferts d'hydrogenes

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Le, Blanc Alain. "Réactions unimoléculaires en phase gazeuse, de radicaux cations bifonctionnels beta céto-alcool, beta céto-esters et de cations beta céto-acylium /." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb376150730.

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Dissertations / Theses on the topic 'Cations'

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