Ruthenium-catalyzed azide alkyne cycloaddition reaction: scope, mechanism and applications

The ruthenium-catalyzed azide alkyne cycloaddition (RuAAC) affords 1,5-disubstituted 1,2,3-triazoles in one step and complements the more established copper-catalyzed reaction providing the 1,4-isomer. The RuAAC reaction has quickly found its way into the organic chemistry toolbox and found applications in many different areas, such as medicinal chemistry, polymer synthesis, organocatalysis, supramolecular chemistry, and the construction of electronic devices. This Review discusses the mechanism, scope, and applications of the RuAAC reaction, covering the literature from the last 10 years

Assessing the inhibitory potential of natural silicon oil on brass degradation in 1M H2SO4

Assessment of silicon oil as natural inhibitor on brass in 1 M H2SO4 acid solution has been studied using linear potentiodynamic polarization and gravimetric method in the inhibited concentration variation between 2% to 10% range. Tafel extrapolation techniques were used to obtain corrosion potential (Ecorr) and corrosion current density (Icorr). From all indication, the inhibitor is of mixed type. The adsorption behavior occurs on the surface of brass due to the presence of the absorbed complex atom from the oil. The calculated portion of the surface covered from the corrosion process follows Langmuir adsorption Isotherm

NASA SBIR abstracts of 1991 phase 1 projects

The objectives of 301 projects placed under contract by the Small Business Innovation Research (SBIR) program of the National Aeronautics and Space Administration (NASA) are described. These projects were selected competitively from among proposals submitted to NASA in response to the 1991 SBIR Program Solicitation. The basic document consists of edited, non-proprietary abstracts of the winning proposals submitted by small businesses. The abstracts are presented under the 15 technical topics within which Phase 1 proposals were solicited. Each project was assigned a sequential identifying number from 001 to 301, in order of its appearance in the body of the report. Appendixes to provide additional information about the SBIR program and permit cross-reference of the 1991 Phase 1 projects by company name, location by state, principal investigator, NASA Field Center responsible for management of each project, and NASA contract number are included

Synthesis, Characterization, And Catalytic And Biological Activities of A Mixed-ligand Cobalt(ii) Bipyridyl/diphenylazodioxide Complex

Transition metal complexes have immense importance in the pharmaceutical industry. These types of complexes can be useful catalysts in the synthesis of medicinal compounds and can act as anticancer drugs. In these pharmaceutical applications, 1st-row transition metal-containing complexes offer certain advantages compared to their 2nd and 3rd-row transition metal counterparts. Our motivation was to investigate pharmaceutical applications of transition metal complexes containing both a 1st-row transition metal and unusual ligands to expand the knowledge of a class of complexes that could potentially be beneficial in the pharmaceutical industry. A class of rare ligands that piqued our interest was that of the diaryl azodioxides, cis-Ar(O)NN(O)Ar, which belong to the wider class of organic derivatives of nitric oxide (NO). Our synthesis and pharmaceutical applications of the azodioxide complex salt [Co(bpy){Ph(O)NN(O)Ph}2](PF6)2 have been able to significantly expand the knowledge of azodioxide complexes by displaying an unusual trigonal prismatic coordination geometry for cobalt(II) with only bidentate ligands, showing evidence of ligand-based redox activity, acting as an active catalyst in allylic amination/C-C double-bond transposition reactions, and selectively inducing apoptosis in SK-HEP-1 human liver adenocarcinoma cells. Importantly, catalytic and biological studies of [Co(bpy){Ph(O)NN(O)Ph}2](PF6)2 are ongoing, and focused on its potential for use in the pharmaceutical industry as a drug or catalyst for drug synthesis. Future work will vi involve comparing the catalytic and biological activities of [Co(bpy){Ph(O)NN(O)Ph}2](PF6)2 with other azodioxide complexes prepared by our group to identify structure-activity relationships and inform the design of more efficient catalysts and anti-cancer, pro-apoptotic agents

The application of green chemistry and engineering to novel sustainable solvents and processes

The implementation of sustainable solvents and processes is critical to new developments in reducing environmental impact, improving net efficiency, and securing economic profitability in the chemical and pharmaceutical industries. In order to address the challenge of sustainability, researchers have used switchable solvents for both reaction and separation by utilizing a built-in switch to undergo a step change in chemical and physical properties. This allows us to facilitate reactions in the solvent then activate the switch to enable separation and facile product recovery. Subsequently, we can recover the solvent for reuse and avoid energy- or waste-intensive separation processes; thus we are developing and using these switchable solvents as sustainable and environmentally benign alternatives to traditional processes. In this research, we enable the sustainable scale-up of a switchable solvent - piperylene sulfone - a "volatile" and recyclable DMSO replacement. In the development of this process, we improved the reaction performances and developed a green purification method. Furthermore, we enable and demonstrate the implementation of a Meerwein-Ponndorf-Verley (MPV) reduction, a pharmaceutically relevant reaction, into a continuous flow platform. The innovation of continuous flow processes can replace traditional batch reaction technology, and is indeed a key research area that has been acknowledged by the pharmaceutical industry. Additionally, we utilize the switchable sulfone solvents, piperylene and butadiene sulfone, for reaction and separation of HMF produced from monosaccharides as an alternative to a process which has been limited by an inefficient separation step.PhDCommittee Chair: Eckert, Charles; Committee Co-Chair: Liotta, Charles; Committee Member: Fernandez, Facundo; Committee Member: Meredith, Carson; Committee Member: Teja, Amy

Biocatalysis: Chemical Biosynthesis

This book has been written with the purpose of providing a vision of a topic which is on the edge of biology and chemistry. As well, we want to provide an updated vision of the potentials and limitations of biocatalysis, especially with respect to applications in processes of organic synthesis, fine chemicals, and medicine. This book pretends to illustrate the potential of an excellent overview of recent progress on the assessment of granted patents as a useful tool in asymmetric synthesis. Some distinguished researchers have contributed to this endeavor with their knowledge, their commitment and their encouragemen

Mechanocatalytic conversion of (Ligno)cellulosic biomass: kinematic modelling of the milling process and experimental methods for product valorisation

Lignocellulosic biomass is a promising renewable feedstock that could replace fossil resources to produce valuable chemicals and biofuels. However, the conversion of lignocellulose requires sophisticated pretreatment processes to efficiently depolymerise and separate its polymeric components (i.e. lignin, cellulose and hemicellulose). In this framework, the mechanocatalytic depolymerisation (MCD) of biomass has emerged as a promising method. Ball-milling of an acid-impregnated substrate generates highly depolymerised, water-soluble products (WSP), which can be further hydrolysed under low severity conditions to provide two isolated streams: depolymerised lignin and C5/6 sugars. Despite these promising results, the mechanisms underlying MCD are poorly understood, and additional product separation and purification methods must be developed to exploit the full potential of MCD on an industrial scale. In this Thesis, kinematic modelling approaches were applied to three different ball mills to estimate the mechanical energy transferred to the substrate during the MCD process. Experimental setups using varied milling parameters revealed crucial correlations between the apparent energy transfer and WSP formation during the processing of α-cellulose and beechwood. The results highlight the fundamental importance of the geometry, working principle and process settings of a ball mill for its effectiveness in momentum transfer. Furthermore, this Thesis investigates the separation of the WSP through adsorption on a benzene-derived microporous organic polymer (MOP). The selective recovery of the adsorbed material by desorbing the polymer with solvents of different polarity in sequence represents an alternative technique to effectively fractionate the WSP according to their molecular weight, elemental composition and lignin content. Finally, this Thesis presents an effective technique to purify the sugar stream produced by the MCD of lignocellulose and subsequent hydrolysis for biotechnological applications. Thereby, the reusable benzene MOP was used to selectively adsorb furfurals and phenolic lignin residues, which have proven as toxic inhibitors for microbial activity, yielding high-quality sugars for ethanol fermentation.Open Acces

Nanoengineering heterogeneous catalysts for the selective hydrogenation of key agrochemical and industrial derivatives

Selective hydrogenation through tailored catalysts for both agrochemical and commercial chemical precursors opens the potential for low energy and low waste production within both industries. For the purposes of this work, catalyst series with varying loadings of palladium nanoparticles were prepared upon both amorphous silica, and the structured mesoporous SBA-15. Full and extensive characterisations of both series were performed, and comparisons between the two made. For work focusing on agrochemical derivatives, research was done using the simplified reference chemical crotononitrile. A wide range of systematic screenings were performed to identify the effect of a variety of variables upon the activity and selectivity of the reaction These included the effect of metal loading, catalyst mass, temperature, hydrogen pressure, and perturbation. Results indicated a poor selectivity towards nitrile hydrogenation within mild conditions, with more notable results within higher pressures Key findings within the crotononitrile work highlighted a retardation effect within higher pressures. Extensive work including beam-time at the Diamond Light Source synchrotron allowed for the successful identification of palladium-hydride in-situ. As a result, a positive correlation was formed between hydride formation and the retardation of the nitrile selectivity due to its effect upon the active sites of the catalyst. For the work looking at the commercial aspect of selective hydrogenation, the conversion of cinnamaldehyde to cinnamyl alcohol was reviewed. Utilising the same catalyst series identified in previous research, a similar screening of reaction conditions and their effects upon the activity and selectivity were performed. With key comparisons to previous work within the group utilising platinum-based catalysts, it was concluded that palladium exhibited a much higher activity but at the cost of lowered selectivity towards aldehyde hydrogenation. Additionally, with previous work espousing the effect of alignment within cinnamaldehyde hydrogenation, it was noted that palladium was much less beholden to the effects of support polarity due to silanol species. Parallel work on sterically inhibiting moieties within benzaldehyde test reagents also highlighted a strong effect on catalytic activity due to poor metal-reagent surface alignment

Creating a Voice for Black Tech Entrepreneurs in Academic Literature

In a country where inventors and innovators are noted as being at liberty to enter and contribute to the free market space, conversely studies have found that Black tech entrepreneurs face greater difficulty launching and growing their businesses. A review of the literature suggests that many of these difficulties stem from the lingering effects of historical inequalities. These inequalities have existed for decades due to laws and regulations that once limited home ownership, income earning, credit access, inheritances, and educational opportunities. Additionally, literature in the tech arena has demonstrated a lack of diversity in the field. Pattern matching or preconceived standards have also been said to impact Black tech entrepreneurs’ opportunities to receive investments to launch and grow their businesses. While great dialogue has taken place in the tech arena around these disparities, little is known in academic literature about how Black tech entrepreneurs engage in the process of creating innovative brands and marketing their companies. In light of this, the researcher conducted a qualitative case study designed to explore black tech entrepreneurs’ perceptions of how they learn to launch and grow their businesses. This study engaged participants who self-identified as tech entrepreneurs of Black or African descent who have launched apps, websites, or hybrid companies in the United States. Among the key findings that emerged from the study were: An overwhelming majority of participants described that seeking the counsel of “expert” others was a key action in securing funding to grow their companies. Further, a strong majority of participants indicated that having a positive self-concept was a key facilitator in growing their businesses; while, an equal number indicated that a misalignment between the investor and entrepreneur inhibited their ability to grow. The tech entrepreneurial field can evolve through the increased trying on of differing perspectives by both investors and entrepreneurs; the continued development of diversity tech ecosystems and support networks; and, sustained progress in increasing the investment opportunities for Black tech entrepreneurs