Philosophiae Doctor - PhD / A variety of nitrogen based dendritic ligands have been synthesized and used in copper mediated Atom Transfer Radical Polymerization (ATRP) of MMA. These ligands were derived from the commercially available Generation 1 polypropyleneimine dendrimer DAB-(NH2)4. The first set of ligands was synthesized by reacting DAB-(NH2)4 with aromatic aldehydes such as 2-pyridinecarboxyaldhyde and 4-t-butyl benzaldehyde to form imine functionalized dendrimers. Analogous secondary amine functionalized dendrimers were also synthesized by reducing the abovementioned imine functionalized dendrimers using sodium borohydride. The ligands produced were characterized by 13C / 1H NMR, and infra-red spectroscopy as well as elemental analysis to confirm its structure. The ligands were then used in copper mediated ATRP of MMA. The resulting polymer solutions were analyzed by Gas Chromatography (GC) to monitor the monomer conversion while the isolated polymers were analyzed by gel permeation chromatography (GPC) for molecular weight determination. Results showed that the primary and secondary amine and imine dendritic ligands were not efficient in promoting ATRP reactions. This led to the modification of DAB-(NH2)4 using methyl methacrylate to replace the peripheral amino groups of the DAB-(NH2)4 with tertiary amine groups. A second generation tertiary amine dendrimer was also synthesized in a similar fashion. The ligands obtained were then characterized using 13C and 1H NMR spectroscopy. The tertiary amine dendrimers were used in copper mediated ATRP of MMA. The polymerization medium was analyzed over time using GC to monitor monomer conversion while GPC was used for molecular weight determination of the resulting polymers. The results obtained using the methyl methacrylate modified ligands indicated that in the case of MMA polymerization, these ligands essentially conformed to the requirements of a good ATRP system. However in the preliminary studies, when employed in copper mediated ATRP of styrene, these ligands did not perform well. Further investigation is needed to improve the performance of these ligands in styrene polymerization under ATRP conditions. / South Africa

The entirety of the investigation discussed in this paper was confined to a study of the spin resonance properties of unpaired electrons of an organic free radical. In the remainder of the paper the theory of electron spin resonance, the apparatus used in the investigation, and the experimental results obtained are discussed in that order.

This project presents findings from an analysis of qualitative interviews by the J20 Defendants, who were arrested, detained, and charged for rioting Donald J. Trump’s inauguration on January 20, 2017. This project examines the identity management strategies and experiences of the J20 Defendants as individual members and as a larger collective, with specific focus on how their mental and emotional health impacts their perception of self. In addition, this project uses Fantasy Theme Analysis (FTA) to identify organizational norms and communicative practices within the J20 collective. Time and space impact collective interpretations, meanings, and values, which influence group consciousness (Bormann, 1985; Bormann, Cragan, & Shields, 1994). To understand the defendants’ symbolic world, I describe in Chapter 1 what happened on January 20, 2017. I explain, in chronological order, how the J20 Defendants were detained, their collective experience while in police custody, and the court proceedings.Attending Disrupt J20 was a collective experience, Weick (1979) explains that shared interpretations among members grant organizations the ability to exist beyond, or even without, physical or systematic structures. Chapter 2 defines the J20 Defendants as an organization through the Four Flows Models, a school of thought within Communicative Constitution of Organization (CCO). The J20 Defendants are anunusual organization due to forced membership; the prosecution labels their identities. However, they made sense of their forced membership by utilizing the four processes within the Four Flows Model: (1) membership negotiation, (2) self-structuring, (3) activity coordination, and (4) institutional positioning. This project also defines the J20 Defendants as a stigmatized organization through the theoretical concepts of event and core stigma, which are defined in Chapter 2. The defendants managed their stigma through various identity management strategies, which are highlighted in Chapter 4. Findings suggest the defendants did not value the viewpoint of mainstream society, which is why they attended the stigmatizing event Disrupt J20. However, they did value the opinions of other activists.Despite having similar beliefs and values, the defendants each navigated their stigma differently. Furthermore, the ways the defendants managed stigma did not align with strategies articulated in organizational communication literature. However, every interviewee made sense of their stigma based on their ability to maintain confidentially. This project notes three organizational obstacles: (1) managing the stress and anxiety of being a member, (2) communicating internally, (3) externally performing a clear collective identity. Through various forms of comradery, members were able to manage their stress and anxiety as J20 Defendants. Members were also viewed as autonomous agents in how active or inactive they wanted to be. Every defendant interviewed stepped away from the organizational core temporarily or permanently. Overall, I hope this project illuminates new information about stigmatized organizations that seek cultural and political change.

Thesis advisor: Xiao-Xiang Zhang / Thesis advisor: James Morken / This dissertation will present three projects focusing on the development of stereoselective radical cascade reactions via metalloradical catalysis (MRC) using Co(II) D2-symmetric chiral amidoporphyrins [Co(D2-Por*)] as the catalyst. The first project demonstrated the feasibility of applying MRC for asymmetric radical cascade processes by achieving an enantioselective radical bicyclization of 1,6-enynes with diazo compounds, which constructed multi-substituted cyclopropane-fused tetrahydrofurans bearing three contiguous stereogenic centers and one trisubstituted alkene. Detailed mechanistic studies including EPR studies and DFT calculation unveiled a radical-based stepwise mechanism. The synthetic utility of this reaction was demonstrated by a series of diastereoselective transformations of the bicyclic products. In the second project, this strategy was expanded to the application of Co(II)-based MRC to catalyze radical cascade reactions involving hydrogen-atom abstraction (HAA) process. A broad array of homopropargyl ethers reacted with diazo compounds to generate enantiomerically enriched ɑ,β-disubstituted tetrahydrofurans in good yields with high diastereoselectivities and enantioselectivities. The third project explored the utilization of the established strategy to accomplish more challenging bicyclization of 1,6,8-dienynes for the construction of cycloheptadiene-fused tetrahydrofurans in regio- and diastereoselective fashions. Such 5,7-fused ring system has been widely found in natural products and bioactive species. / Thesis (PhD) — Boston College, 2022. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

<p> Three electronic absorption systems of the fluorosulfate radical in the gas phase have been observed in the near infrared and visible regions of the spectra and have been assigned to the electronic transitions 2E(2) - 2A2, 2E(l)- 2A2 and 2A1- 2A2 . Molecular orbital calculations on the fluorosulfate radical have been done in order to aid the interpretation of the electronic spectra of the radical. Vibrational and rotational analyses of the visible absorption system ( 2E (2)- 2A 2) have been carried out. The geometry of the radical in the upper 2 E(2) state has been found to be similar to that of the 2A2 ground state. The ground state fundamental frequencies of the radical have been determined. The presence of a Jahn-Teller-spin-orbit interaction has been proposed for the 2E(2) state. </p> / Thesis / Doctor of Philosophy (PhD)

No description available.

No description available.

This research aims to refresh and reinterpret the radical theory of associative rings using the base radical and base semisimple class constructions. It also endeavours to generalise some results about ideals of rings in terms of accessible subrings. A characterisation of accessible subrings is included. By applying the base radical and base semisimple class constructions to many of the known results in established radical theory a number of gaps are uncovered and closed, with the goal of making the theory more accessible to advanced undergraduate and graduate students and mathematicians in related fields, and to open up new areas of investigation. After a literature review and brief reminder of algebra rudiments, the useful properties of accessible subrings and the U and S operators independent from radical class connections are described. The section on accessible subrings illustrates that replacing ideals with accessible subrings is indeed possible for a number of results and demonstrates its usefulness. The traditional radical and semisimple class definitions are included and it is shown that the base radical and base semisimple class constructions are equivalent. Diagrams illustrating the constructions support the definitions. From then on, all radical and semisimple classes mentioned are understood to have the base radical and base semisimple class form. Subject to the constraints of this work, many known results of traditional radical theory are reinterpreted with new proofs, illustrating the potential to simplify the understanding of radical theory using the base radical and base semisimple class constructions. Along with reinterpreting known results, new results emerge giving further insight to radical theory and its intricacies. Accessible subrings and the U and S operators are integrated into the development. The duality between the base radical and base semisimple class constructions is demonstrated in earnest. With a measure of the theory presented, the new constructions are applied to examples and concrete radicals. Context is supported by establishing the relationship between some well-known rings and the radical and related classes of interest. The title of the thesis, Towards a Reinterpretation of the Radical Theory of Associative Rings Using Base Radical and Base Semisimple Class Constructions, reflects the understanding that reinterpreting the entirety of radical theory is beyond the scope of this work. The conclusion includes an outlook listing further research that time did not allow.

Lyconadin A (1) is a structurally unique Lycopodium alkaloid with antitumor properties, isolated from the club moss Lycopodium complanatum. We are developing a synthetic route to 1 based on a novel 7-exo-trig/6-exo-trig acyl radical cascade cyclization. The synthesis of model acyl radical cascade precursor 23 will be presented. Key features of this synthesis include the suppression of competing elimination during the alkylation of a hindered phenethyl bromide and the use of a lactone as a precursor to a compound bearing two differentially protected primary alcohols. An account of our studies on the model acyl radical cascade cyclization (23 to 24 above) will also be given, including a stereochemical analysis of the product. Our findings have been applied to develop a more detailed stereoselective synthetic plan for Lyconadin A (1).

Ce travail porte sur le greffage radicalaire de l'anhydride maléique sur un polyéthylène basse densité, en voie fondu, et en présence d'un abstracteur d'atome d'hydrogène. L'utilisation des radicaux nitroxyle, comme agent de terminaison, en présence d'un peroxyde a permis de bloquer la réaction de réticulation du polyéthylène, réaction secondaire fréquemment rencontré lors de l'utilisation de radicaux peroxyle, tout en permettant le greffage d'une faible quantité d'anhydride maléique. L'élimination d'une partie de l'anhydride maléique et des radicaux nitroxyle via des réactions secondaires à haute température semble toutefois inévitable. La substitution du peroxyde par une alcoxyamine dans le rôle d'abstracteur d'atome d'hydrogène a alors permis d'atteindre des taux de greffage en anhydride maléique supérieurs pour une modification des propriétés rhéologiques du polyéthylène équivalente. Néanmoins, des incertitudes demeurent encore sur le mécanisme de décomposition thermique de cette alcoxyamine permettant la réaction de greffage. / This work deals with melt grafting of maleic anhydride onto low density polyethylene using radical initiators which are able to abstract hydrogen from the polyolefin backbone. The use of a nitroxide radical as a termination reagent in presence of peroxide allowed to prevent the polyethylene crosslinking during the maleic anhydride grafting. Indeed, the polyethylene crosslinking is the main side reaction but the elimination of a small proportion of the reagents (monomer and nitroxide radical) through other side reactions seems to be unavoidable. The peroxide substitution by an alcoxyamine leaded to a higher grafted maleic anhydride rate for the same polyethylene rheological modification. Nevertheless, the thermal decomposition mechanism of the alcoxyamine which makes the grafting reaction possible is still uncertain.