In this thesis it will be shown that the hydrogen atom has a SU(2) × SU(2) symmetry generated by the quantum mechanical angular momentum and Runge-Lenz vector operators. Additionally, the hydrogenic atom will be studied with supersymmetric methods to identify a supersymmetry that relates different such systems. This thesis is intended to present the material in a manner accessible to people without background in Lie groups and supersymmetry, as well as fill in some calculations between steps that are not spelt out in the litterature.

Solvent-free peroxide-initiated polymer modifications are widely used to improve the physical and/or chemical properties of commodity plastics and elastomers. Although the reactions that underlie polymer grafting are known, our understanding of H-atom transfer reactions in this context is incomplete. Fundamental questions remain unanswered, such as the difference in reactivity between different polymers (polyethylene versus polypropylene and polyisobutylene) and differences in the regiochemical outcomes of grafting reactions upon them. Herein, experimental data pertaining to the H-atom transfers involved in polyolefin graft modifications were obtained to improve our fundamental understanding of these reactions by using radical-trapping techniques and quantum chemical calculations. In this project, experimental measurements of the efficiency of H-atom abstraction by t-butoxyl radicals from polyolefins, and suitable model compounds such as pentane, 2,4-dimethylpentane and 2,2,4,4-tetramethylpentane were determined. Insight is gained from alkyl-trapping experiments to quantify the relative reactivities of the primary, secondary and tertiary positions of the model compounds. Experimental data were compared to quantum chemical calculations, which revealed that entropic effects dictate the regioselectivity and preclude abstraction at the secondary position in favour of the less enthalpically-favourable primary abstraction site. MP2 and CBS-QB3 level calculations were able to reproduce experimental trends in model compound reactivity, while the highly common B3LYP density functional, used in other investigations on the subject, could not. / Thesis (Master, Chemical Engineering) -- Queen's University, 2011-10-20 16:48:38.083

No description available.

Environmental pollution has been a serious concern worldwide. Many degradation methods have been developed to clean sites contaminated with pollutants. More knowledge and better understanding in this field will help to protect our environment. The goal of the research in this thesis is to gain a better understanding of the mechanism of organic pollutant degradation in Fenton reactions and sonochemical reactions. Fenton degradation uses hydroxyl radical to oxidize organic compounds. The radical is produced by catalytic decomposition of hydrogen peroxide with Fe(II). Further research has found that addition of cyclodextrins can enhance degradation efficiency of hydrophobic organic pollutants. To study the mechanism of the enhancement, pollutant-cyclodextrin-Fe(II) aqueous systems were studied by fluorescence and NMR techniques. The results indicated the formation of pollutant/carboxymethyl-â-cyclodextrin/Fe(II) ternary complexes in the solution. With the ternary complex, the catalyst Fe(II) becomes closer to the pollutant, therefore leading to more efficient hydroxyl radical attack on the pollutant. Additional studies showed that hydropropyl-â- cyclodextrin, â-cyclodextrin and á-cyclodextrin bound pollutant well, but bound Fe(II) poorly. Sulfated-â-cyclodextrin did not bind well with pollutant although it bound Fe(II) well. Sonochemical degradation is another important pollutant treatment method in practice. It was found that phenol sonolysis can be enhanced by volatile hydrogen atom scavengers such as carbon tetrachloride and perfluorohexane. The non-volatile hydrogen atom scavenger iodate did not enhance phenol degradation. The first order rate constant for aqueous phenol degradation increased by about 2.2-2.8 times in the presence of 150 ìM carbon tetrachloride. In the presence of less than 1.5 ìM perfluorohexane the first order rate constant increased by about 2.3 times. Hydroquinone was the major observed reaction intermediate both in the presence and absence of hydrogen atom scavengers. Hydroquinone yields were substantially higher in the presence of hydrogen atom scavengers, suggesting that hydroxyl radical pathways for phenol degradation were enhanced by the hydrogen atom scavengers. The additives investigated in this study have potential to improve pollutant degradation efficiency. Other fields may also benefit from the information gained in this study. For example the improvement could be achieved in synthetic processes that rely on hydroxyl radical as a key intermediate.

Thesis advisor: Peter X. Zhang / Thesis advisor: James P. Morken / Radical reactions have attracted continuous research interest in recent year considering their diverse reactivities. Hydrogen-atom abstraction (HAA), as one type of the most well-explored radical reactions, has been identified as one of powerful tools for C–H functionalization. Reactions involving 1,4-HAA, which is typically a challenging process both entropically and enthalpically, are rather scarce, while 1,5-HAA have been well demonstrated for variety of synthetic applications. Guided by the concept of metalloradical catalysis (MRC), 1,4-HAA was for the first time utilized as the key step to achieve asymmetric construction of chiral ring structures: cyclobutanones, azetidines and tetrahydropyridines. The design of different D2-symmetric chiral amidoporphyrin as the supporting ligand is the key to all these transformations. The reactions can be conducted under mild conditions, affording corresponding ring structure in good yields with excellent selectivity. Furthermore, The combined computational and experimental studies have shed light on the mechanistic details of these new asymmetric radical intramolecular C–H alkylation processes, which are fundamentally different from existing catalytic systems involving metallocarbenes for concerted C–H insertion. We envision that these asymmetric radical processes via Co(II)-based MRC could become an alternative method for important chiral ring structures synthesis and potentially provide new opportunities for complex molecule construction. / Thesis (PhD) — Boston College, 2022. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

The flavin-containing monoamine oxidases (MAO) A and B catalyze the oxidative deamination of primary and secondary amines. The overall process involves a two electron oxidation of the amine to the iminium with concomitantreduction of the flavin. Based on extensive studies with a variety of chemical probes, Silverman and colleagues have proposed a catalytic pathway for the processing of amine substrates and inactivators by MAO-B that is initiated by a single electron transfer (SET) step from the nitrogen lone pair to the oxidized flavin followed by α-proton loss from the resulting amine radical cation that leads to a carbon radical. Subsequent transfer of the second electron leads to the reduced flavin and the iminium product. In the case of N-cyclopropylamines, the initially formed amine radical cation is proposed to undergo rapid ring opening to form a highly reactive primary carbon centered radical that is thought to be responsible for inactivation of the enzyme. In this thesis we have exploited the unique substrate and inactivator properties of 1,4-disubstituted tetrahydropyridine derivatives to probe the mechanism of MAO-B catalysis. Reports of the parkinsonian inducing neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) as a structurally unique substrate of MAO-B initiated these studies. Consistent with the SET pathway, the N-cyclopropyl analog of MPTP proved to be an efficient time and concentration dependent inactivator but not a substrate of MAO-B. On the other hand, the 4-benzyl-1-cyclopropyl analog is both a substrate and inactivator of MAO-B. These properties may not be consistent with the obligatory formation of a cyclopropylaminyl radicalcation intermediate. In an attempt to gain further insight into the mechanism associated with the MAO catalyzed oxidation of 1,4-disubstituted tetrahydropyridines, deuterium isotope effects studies on both the substrate and inactivation properties of the 4-benzyl-1- cyclopropyl derivative were undertaken. A series of 1-methyl- and 1-cyclopropyltetrahydropyridine derivatives bearing various heteroaro-matic groups at C-4 also have been examined. The MAO-B substrate properties, inactivator properties and partition ratios for these compounds together with preliminary results from chemical model studies are discussed in terms of the MAO-B catalytic pathway. / Ph. D.

The path integral formulation of quantum mechanics generalizes the action principle of classical mechanics. The Feynman path integral is, roughly speaking, a sum over all possible paths that a particle can take between fixed endpoints, where each path contributes to the sum by a phase factor involving the action for the path. The resulting sum gives the probability amplitude of propagation between the two endpoints, a quantity called the propagator. Solutions of the Feynman path integral formula exist, however, only for a small number of simple systems, and modifications need to be made when dealing with more complicated systems involving singular potentials, including the Coulomb potential. We derive a generalized path integral formula, that can be used in these cases, for a quantity called the pseudo-propagator from which we obtain the fixed-energy amplitude, related to the propagator by a Fourier transform. The new path integral formula is then successfully solved for the Hydrogen atom in two and three dimensions, and we obtain integral representations for the fixed-energy amplitude. / Vägintegral-formuleringen av kvantmekanik generaliserar minsta-verkanprincipen från klassisk mekanik. Feynmans vägintegral kan ses som en summa över alla möjliga vägar en partikel kan ta mellan två givna ändpunkter A och B, där varje väg bidrar till summan med en fasfaktor innehållande den klassiska verkan för vägen. Den resulterande summan ger propagatorn, sannolikhetsamplituden att partikeln går från A till B. Feynmans vägintegral är dock bara lösbar för ett fåtal simpla system, och modifikationer behöver göras när det gäller mer komplexa system vars potentialer innehåller singulariteter, såsom Coulomb--potentialen. Vi härleder en generaliserad vägintegral-formel som kan användas i dessa fall, för en pseudo-propagator, från vilken vi erhåller fix-energi-amplituden som är relaterad till propagatorn via en Fourier-transform. Den nya vägintegral-formeln löses sedan med framgång för väteatomen i två och tre dimensioner, och vi erhåller integral-representationer för fix-energi-amplituden.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A possibilidade da existência de átomos de hidrogênio estáveis em dimensões superiores a três é abordada. O problema da dimensionalidade é visto como um problema de Física, no qual relacionam-se algumas leis físicas com a dimensão espacial. A base da análise deste trabalho faz uso das equações de Schrödinger (não relativística) e de Dirac (relativística). Nos dois casos, utiliza-se a generalização tanto do setor cinemático bem como o setor de interação coulombiana para variar o parâmetro topológico dimensão. Para o caso não relativístico, os auto-valores de energia e as auto-funções são obtidas através do método numérico de Numerov. Embora existam soluções em espaços com dimensões superiores, os resultados obtidos no presente trabalho indicam que a natureza deve, de alguma maneira, se manifestar em um espaço tridimensional. / The question of whether hydrogen atoms can exist or not in at spaces with a number of dimensions D greater than 3 is revisited. The dimensionality problem is taken as physical one, which physics laws are related to the space dimension. The main framework of the analysis through out this tesis are the Schrödinger Equation (non relativistic) and the Dirac Equation (relativistic). Both cases use the kinematic and Coulombian interaction sectors generalized in order to vary the topological paramenter dimension. For the non relativistic case, eigenvalues of energy and eigenfunctions are evaluated using the Numerov numerical method. Although there are solutions in higher dimensions, the results obtained in this tesis indicate that nature should somehow prefer a tridimensional space.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A possibilidade da existência de átomos de hidrogênio estáveis em dimensões superiores a três é abordada. O problema da dimensionalidade é visto como um problema de Física, no qual relacionam-se algumas leis físicas com a dimensão espacial. A base da análise deste trabalho faz uso das equações de Schrödinger (não relativística) e de Dirac (relativística). Nos dois casos, utiliza-se a generalização tanto do setor cinemático bem como o setor de interação coulombiana para variar o parâmetro topológico dimensão. Para o caso não relativístico, os auto-valores de energia e as auto-funções são obtidas através do método numérico de Numerov. Embora existam soluções em espaços com dimensões superiores, os resultados obtidos no presente trabalho indicam que a natureza deve, de alguma maneira, se manifestar em um espaço tridimensional. / The question of whether hydrogen atoms can exist or not in at spaces with a number of dimensions D greater than 3 is revisited. The dimensionality problem is taken as physical one, which physics laws are related to the space dimension. The main framework of the analysis through out this tesis are the Schrödinger Equation (non relativistic) and the Dirac Equation (relativistic). Both cases use the kinematic and Coulombian interaction sectors generalized in order to vary the topological paramenter dimension. For the non relativistic case, eigenvalues of energy and eigenfunctions are evaluated using the Numerov numerical method. Although there are solutions in higher dimensions, the results obtained in this tesis indicate that nature should somehow prefer a tridimensional space.

Les recherches présentées dans ce manuscrit s’articulent autour de deux parties distinctes. La première partie concerne une étude mécanistique de la réaction de décomposition de l’acide formique (AF) photocatalysé par le Tetra-n-ButylAmmonium DecaTungstate (TBADT) et explore la réactivité de ce photocatalyseur envers l’AF. La deuxième partie de ces travaux se focalise sur l’étude de la réactivité radicalaire d’anions phosphorés et de leurs analogues chalcogénés. Dans un premier temps, nous nous sommes intéressés à exploiter la réactivité de phosphures-borane et des anions d’oxydes de phosphine pour la formation de liaisons C-P par photo-induction dans le visible. Dans un second temps, nous avons exploré la réactivité radicalaire et ionique des phosphures-borane chalcogénés, par une étude de leur structure et de leur réactivité. Ces propriétés ont été mises en application dans le cadre de réactions de photo-polymérisation radicalaire et de réduction de composés électrophiles. / This dissertation is organized in two distinct parts. The first one is a mechanistic investigation of the photocatalyzed reaction of decomposition of formic acid (AF) under mild conditions using Tetra-n-ButylAmmonium DecaTungstate (TBADT). The second part of this work revolve around the use and study of the radical reactivity of phosphorous anions and their chalcogenated analogues. Firstly, we used the radical reactivity of phosphido-borane and phosphine oxide anions for the formation of C-P bonds. In a last part, we explored the radical and ionic reactivity of chalcogenated phosphido-borane, by studying their structure and reactivity. These properties has been applied to radical photo-polymerization reactions and for the reduction of electrophiles.