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Advances Toward the Sustainable Production of Novel Musk Compounds
Get PDFMacrocyclic musk ketones are popular base notes in a diverse array of fragrance products ranging from perfumes and colognes to candles and air fresheners. Today, most musk odorants used in the aroma industry are produced synthetically due to ethical and sustainability concerns related to the extraction of natural musk from animal sources. For this reason, extensive computational and synthetic efforts have focused on elucidating the structure-odor relationship of various musk ketones to effectively propose and design novel analog structures. In this work, the green and practical syntheses of four macrocyclic musks were investigated utilizing a renewable and readily available monounsaturated Ω-9 fatty acid, oleic acid, as the starting material. Two of the compounds, muscone (3-MCP 1a) and dihydrocivetone (15), are known aroma chemicals of commercial relevance whereas the two others, 3-methylcyclononadecanone (3-MCN 2) and 3-methylcycloheptadecanone (3-MCH 17), are novel macrocyclic analogs of ring sizes 19 and 17, respectively. Guided by structural optimization tools and drug-protein docking software, (R)-2 and (R)-17 were predicted to bind to human olfactory receptor 5AN1 with affinities that are 11% and 10%, respectively, higher than those of (R)-muscone. Based on this analysis, efforts toward the total syntheses of 3-MCN 2 and 3-MCH 17 were initiated. Even though this experimental work was not concluded, a series of useful advances was made and the reported results may serve as a framework for future studies. Similarly, a novel, three-step synthesis of dihydrocivetone, starting from oleic acid, is described in this work and utilizes a pyrolysis-mediated cyclization approach. Additional research should focus on further optimization of the reaction conditions to improve the conversion, yield, and industrial application of the method. Lastly, a six-step, eco-efficient, and green conversion of oleic acid to (R)-muscone was theoretically devised, and translation of this developed route into experimental advances is currently being investigated
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Carboxylated Cellulose Nanofibrils from Agricultural Crop Residues and Their Self-Assembling into Aerogels
Get PDFThe past several decades have witnessed extraordinary developments in the area of naturally sourced functional nanomaterials, including nanocelluloses. Cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs) have been obtained by downsizing higher-ordered cellulose fibers from different sources like hard- and softwood and agricultural biomass. A critical success factor of the industrialization of nanocelluloses has included optimizing the isolation techniques at both the commercial and designer levels. The coupling of mild chemical pretreatment with post-treatment mechanical processing has been the most promising way to obtain nanocelluloses economically. Specifically, the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation method has been the primary pretreatment technique used in academia and industry. Nevertheless, TEMPO remains expensive, corrosive, and toxic. Thus, crucial and emerging challenges of CNF production include stoichiometric optimization of chemicals and better alternatives to the status quo. Today, there are numerous approaches to prepare nanocelluloses, each affording specific chemistry and dimensions. In this thesis, two additional carboxylation routes were applied, including sequential periodate-chlorite oxidation and carboxymethylation, which have been available in the literature but have remained subsidiary to TEMPO and without good reason. All involved heterogeneous reactions on cellulose introducing negatively charged surface carboxylates. The charges aided in fiber defibrillation into CNFs and maintained their homogeneity as electrostatically stabilized aqueous dispersions. Non-wood cellulose feedstock has also been understudied. Thus, rice straw and almond hulls, as agriculture biomasses produced in significant amounts in California and worldwide, served as the supply for cellulose fibers. The use of two cellulose sources and three surface modification processes afforded analysis of both source-linked and process-linked quality attributes of CNFs. For example, oxidation of rice straw cellulose with regioselective TEMPO/NaClO at the primary C6 position gave a quasi-isotropic CNF cross-section. Conversely, C2, C3 regioselective periodate-chlorite oxidation and non-regioselective carboxymethylation routes produced CNFs with anisotropic lateral dimensions or dominant hydrophilic widths to hydrophobic heights and more significant electrostatic and steric effects on the interfaces of CNFs. One interest was in the tendency of CNFs to physically entangle into gels at low <1 w/v% aqueous dispersion, which was advantageous for the macroscopic assembling of CNFs into aerogels. Three-dimensional, high-porosity (>99.5%), and low-density (<8.0 mg/cm3) ice-templated aerogels were the medium for characterizing source- and process-related self-organizing and self-assembling behaviors and functionalities of CNFs. Results confirmed that regardless of source and process, CNFs maintained a high axial ratio and demonstrated Janus-type hydrophilic and hydrophobic surfaces proven by the amphiphilic super absorption of both polar and nonpolar liquids of the aerogels. The ice-template/freeze-dry formation of PC-CNFs and CMCNFs gave stiffer aerogels, displaying the highest toughness and the greatest strengths. This confirmed predominant CNF self-assembling along larger hydrophilic surfaces, demonstrating the importance of the lateral dimensions of CNFs on the mechanical performances of the assembled aerogels. Concerning source, applying the same TEMPO technique on almond hull produced nanofibrils with ultrahigh lateral and axial ratios and residual lignin content. The resulting aerogels exhibited enhanced mechanical performances linked to significant interfibril physical entanglements and lignin as a natural binding agent. As such, even a biomass feedstock of low cellulose content is a promising natural source for less pristine nanofibrils with value-added properties
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The Study of 5-(Chloromethyl)furfural-Derived Nucleophiles
Get PDF5-(Chloromethyl)furfural (CMF) is a versatile, biobased platform molecule that can be made in high yield directly from raw biomass. Although many studies have been dedicated to the applications of CMF, carbon nucleophilicity in CMF-derived molecules remains little explored. This work describes several strategies to prepare and utilize CMF-derived carbon nucleophiles based on the furylogous effect. Biobased 5-(chloromethyl)furoate and 5-methylfuroate esters were directly deprotonated to function as furylogous enolates. The chloromethylfuroates can also participate in Reformatsky-type reactions, giving carbonyl addition products in high yields. This study was extended to furylogous malonate esters, which react well with aromatic aldehydes under Knoevenagel conditions. Biobased synthetic colorants were developed in moderate to excellent yields covering a spectrum from yellow to red.
Through the study and discussion of furylogous enolate chemistry, this work describes continuing efforts to develop practical tools in the synthetic repertoire for converting cellulosic biomass into useful organic molecules
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Sustainable Biomass Utilization: Exploring Advanced Materials and Carbon-Neutral Industrial Products
Get PDFThis Ph.D. thesis investigates the versatile applications of biomass derivatives including cellulose, the most abundant polymer in nature.Chapter 1 provides a general introduction to the research areas covered in this thesis. Chapter 2 explores the utility of trifluoroacetic acid (TFA) as a dispersing medium for cellulose nanocrystals (CNCs), emphasizing its distinctive solvent properties and its ability to stabilize CNC suspensions. The study demonstrates the dispersibility of native CNCs in TFA and investigates the aging of CNC-TFA suspensions, resulting in the gradual addition of trifluoroacetyl groups to the CNC surface. This method is extended to the formation of a nanocomposite with polyethylene terephthalate (PET), presenting a promising strategy for combining organic-soluble polymers with native cellulose.Chapter 3 introduces an innovative concept involving dyes synthesized entirely from biomass-derived platform molecules, specifically 5-(chloromethyl)furfural (CMF), which can be produced directly from cellulose in a one-step reaction. This methodology circumvents the limitations associated with petrochemical-derived dyes and natural colorants. Using a furylogous malonate or furylogous cyanoacetate and biomass-derived aldehydes, the study process generates industrially relevant synthetic colorants with vibrant hues, demonstrating excellent performance and fastness on selected fabrics. The vision of achieving 100% renewable textiles, where both synthetic fibers and dyes are biobased, is discussed, constituting a transformative approach to sustainable wearables.In Chapter 4, the focus shifts to the transformation of CMF into 2,5-diformylfuran (DFF), which is used in the synthesis of the sustainable dyes in Chapter 3, through oxidation with bismuth nitrate pentahydrate. The study spans different scales, and works toward optimizing yields and addressing challenges encountered during scale-up. Techniques such as continuous extraction, sonication, and variations in extraction solvents are employed to enhance reproducibility. Despite the progress made, further work will be necessary to give consistent yields, particularly at larger scales. Collectively, these chapters significantly contribute to the evolving landscape of sustainable materials and processes, showcasing the potential for innovative applications across diverse fields
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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