Browsing by Subject "Olefin metathesis"
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Item Differential sensing of hydrophobic analytes with serum albumins(2012-05) Ivy, Michelle Adams; Anslyn, Eric V., 1960-In the last decade, there has been a growing interest in the use of differential sensing for molecular recognition. Inspired by the mammalian olfactory system, differential sensing employs an array of non-selective receptors, which through cross-reactive interactions, create a distinct pattern for each analyte tested. The unique fingerprints obtained for each analyte with differential sensing are studied with statistical analysis techniques, such as principal component analysis and linear discriminant analysis. It was postulated that serum albumin proteins would be applicable to differential sensing schemes due to significant differences in sequence identity between different serum albumin species, and due to the wide range of hydrophobic molecules which are known to bind to these proteins. Consequently, cross-reactive serum albumin arrays were developed, utilizing hydrophobic fluorescent indicators to detect hydrophobic molecules. As such, serum albumin cross-reactive arrays were employed to discriminate subtly different hydrophobic analytes, and mixtures of these analytes, in the form of terpenes and perfumes, plasticizers and plastic explosive mixtures, and glycerides and adipocyte extracts. In this doctoral work, a detailed review of the field of differential sensing, and a thorough study of principal component analysis and linear discriminant analysis in various differential sensing scenarios, are given. These introductory chapters aid in better understanding the methods and techniques applied in later experimental chapters. In chapter 3, serum albumins, a PRODAN indicator, and an additive are shown to discriminate five terpene analytes and terpene doped perfumes. Chapter 4 describes an array with serum albumins, two dansyl fluorophores, and an additive which successfully differentiate the plasticizers found within the plastic explosives C4 and Semtex and simulated C4 and Semtex mixtures. Discrimination of these simulated mixtures was also achieved with this array in the presence of soil contaminants, demonstrating the potential real-world applicability of this sensing ensemble. Finally, chapter 5 details an array consisting of serum albumins, several fluorescent indicators, and a Grubb's olefin metathesis reaction, to differentiate saturated and unsaturated triglycerides, diglycerides, and monoglycerides. Mixtures of glycerides in adipocyte extracts taken from rats with different health states were then successfully discriminated, showing promise for clinical applications in differentiating adipoctyes from pre-diabetic, type 2 diabetic, and non-diabetic individuals.Item Novel diaminocarbene ligands and their applications in ruthenium-based metathesis catalysts(2010-08) Rosen, Evelyn Louise; Bielawski, Christopher W.; Anslyn, Eric V.; Holliday, Bradley J.; Willson, C G.; Eldridge, R B.With the ever expanding utility of transition metal catalysis, there has been a thrust both to develop catalysts with unique selectivites or activites, and to understand the factors which govern these characteristics at both a fundamental and practical level. Olefin metathesis has become an essential reaction for the synthesis of small molecules in addition to polymeric materials. We have pursued two distinct ligand classes based on diaminocarbenes with novel architectures to address specific limitations within this useful class of reactions: 1) limited access to polymeric materials with controlled microstructures and 2) poor stereoselectivity in Ru-catalyzed cross-metathesis (CM) reactions. Numerous phosphines and N-heterocyclic carbenes (NHCs) have been used as ligands for Ru metathesis catalysts, and the resulting activity is very sensitive to their steric and electronic nature. We envisioned that we could take advantage of this dependence by developing a catalyst with tunable ligand donicity. Redox-switchable ligands can lead to catalysts whose selectivity and/or activity are dependent upon the ligand oxidation state. Towards this purpose, we have developed a ligand which incorporates a 1,1’-disubstituted ferrocene moiety into the backbone of a diaminocarbene (FcDAC). Upon ligation of FcDAC to various transition metals, we were able to use cyclic voltammetry and a spectroelectrochemical FT-IR experiment to show electronic communication between FcDAC and the coordinated metal. We then pursued Ru metathesis catalysts incorporating these ligands. The ring-opening metathesis polymerization of 1,5-cyclooctadiene was studied using [(FcDAC)(PPh₃)Cl₂Ru=(3-phenylindenylid-2-ene)] as the catalyst. Chemical redox reactions were used to establish the ability of FcDAC to impart redox-tunable properties to Ru metathesis catalysts. A new ligand class pioneered in our group, N-aryl,N-alkyl acyclic diaminocarbenes (ADCs), was also studied in various Ru metathesis catalysts. To our delight, these catalysts showed lower E : Z ratios than analogous NHC ligands in two representative CM reactions. We also investigated the conformational diversity of these differentially substituted ADCs given their ability to rotate about their C–N bonds, in particular, to determine how this might influence their donicity. Complexes of the type [(ADC)Ir(COD)Cl] and [(ADC)Ir(CO)₂Cl] were studied, given the wealth of structural and spectral data available for analogous compounds incorporating related ligand classes. Different conformations resulted depending on the N-substituents and the nature of the metal complex. Interestingly, the electron donating ability of ADC ligands was found to depend on their conformation, as evidenced by FT-IR and cyclic voltammetry. This established a new avenue for tuning the donor properties of differentially substituted ADC ligands. The unique properties of these novel ligand classes were demonstrated in Ru metathesis catalysts. However, on a broader level, these ligands are expected to have utility in diverse catalytic applications.Item Olefin production via reactive distillation based Olefin metathesis(2010-12) Morrison, Ryan Frederick; Rochelle, Gary T.; Eldridge, R. Bruce; Ekerdt, John G.; Ellison, Christopher J.; Bielawski, Christopher W.; Seibert, Albert F.Reactive distillation is a combination of a traditional multi-stage distillation column with a chemical reaction. The primary benefits of a reactive distillation process are reduced capital costs for equipment and energy in addition to enhanced conversion for equilibrium-limited reactions. One such equilibrium-limited reaction is an olefin metathesis. Olefin metathesis is a catalyzed reaction that breaks the double bond in olefins and rearranges the alkene fragments into new olefinic products. A comprehensive investigation of a reactive distillation based olefin metathesis and supporting experimentation is documented here. A small pilot plant study was performed for pilot scale performance comparison. Bench reactor experimentation was conducted for the purposes of learning detailed information on specific metathesis reactions. Lastly, a process simulation study was completed for comparison in performance with the small pilot plant process. The small pilot plant study involved the design, construction, testing, operation, and optimization of a reactive distillation column. Continuous operation campaigns at two different hydraulic capacities within the reactive zone were performed and their performances were compared. A higher hydraulic capacity proved to be more efficient and more selective for the conversion of medium molecular weight olefins into both lighter and heavier olefinic products. Bench reactor experiments were designed with the intent of investigating specific alpha olefin metathesis reactions and obtaining conversions, selectivities, and yield structures for future simulation work. However, under conditions similar to that within the small pilot plant process, there existed a high frequency of secondary double bond isomerization (possibly due to an isomerization activity for alumina). There was also an observed dependence on temperature for both the primary metathesis and secondary isomerization reactions. A process simulation representative of the small pilot plant process was constructed in AspenPlus. Using a simplified reaction network based on assumptions and analysis of the reactive zone, its performance was compared with that of the small pilot plant process. The simulation performance tended to underpredict overhead compositions, but accurately simulated the bottoms product composition. Because reactive distillation has not been used with a heavy olefin metathesis reaction, this dissertation demonstrates the uniqueness and effectiveness of a reactive distillation based heavy olefin metathesis.