Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Characterization and Thermal Stability of Acetylated Slicewood Production by Alkali-Catalyzed Esterification.

ABSTRACT: This study was compared and characterized two different alkali (potassium carbonate (PC) and potassium acetate (PA))-catalyzed acetylations of slicewood with vinyl acetate (VA) by a vapor phase reaction. The results revealed that the esterification reaction between VA and the hydroxyl groups of slicewood could be improved by using PC or PA as a catalyst. Additionally, a significant weight percent gain was obtained after VA acetylation with 5% of catalyst. Furthermore, the reactivity of the cellulose hydroxyl groups for VA acetylation was more pronounced at the C2 reactive site compared to acetylation with acetic anhydride. On the other hand, the apparent activation energy of thermal decomposition between 10% and 70% conversion is 174-183, 194-200, and 183-186 kJ/mol for unmodified slicewood and VA-acetylated slicewood with PC and PA, respectively. Accordingly, the thermal stability of the slicewood could be effectively enhanced by VA acetylation, especially for using the PC as a catalyst.

SUBMITTER: Hung KC

PROVIDER: S-EPMC5506890 | biostudies-other | 2017 Apr

REPOSITORIES: biostudies-other

ACCESS DATA

Json Xml

Similar Datasets

Nickel-Catalyzed Esterification of Aliphatic Amides.

Project description:Recent studies have demonstrated that amides can be used in nickel-catalyzed reactions that lead to cleavage of the amide C-N bond, with formation of a C-C or C-heteroatom bond. However, the general scope of these methodologies has been restricted to amides where the carbonyl is directly attached to an arene or heteroarene. We now report the nickel-catalyzed esterification of amides derived from aliphatic carboxylic acids. The transformation requires only a slight excess of the alcohol nucleophile and is tolerant of heterocycles, substrates with epimerizable stereocenters, and sterically congested coupling partners. Moreover, a series of amide competition experiments establish selectivity principles that will aid future synthetic design. These studies overcome a critical limitation of current Ni-catalyzed amide couplings and are expected to further stimulate the use of amides as synthetic building blocks in C-N bond cleavage processes.

| S-EPMC5161497 | biostudies-literature

l-Asparaginase from <i>Aspergillus</i> spp.: production based on kinetics, thermal stability and biochemical characterization.

Project description:This study describes the production of native l-asparaginases by submerged fermentation from Aspergillus strains and provides the biochemical characterization, kinetic and thermodynamic parameters of the three ones that stood out for high l-asparaginase production. For comparison, the commercial fungal l-asparaginase was also studied. Both commercial and l-asparaginase from Aspergillus oryzae CCT 3940 showed optimum activity and stability in the pH range from 5 to 8 and the asparaginase from Aspergillus niger LBA 02 was stable in a more alkaline pH range. About the kinetic parameters, the denaturation constant increased with the heating temperature for all l-asparaginases, indicating that the l-asparaginase activity decreased at higher temperatures, especially above 60 °C. Moreover, l-asparaginase from A. oryzae CCT 3940 remained stable after 60 min at 50 °C. None of the l-asparaginases were inhibited by high NaCl concentrations, which are highly desirable for food industry application. The catalytic activities of all the l-asparaginases were enhanced by the presence of Mn2+ and inhibited by p-chloromercuribenzoate and iodoacetamide. The l-asparaginase from the Aspergillus strains and the commercial enzyme had similar K m when l-asparagine was used as substrate. None of the l-asparaginases, except the l-asparaginase from A. niger LBA 02, could hydrolyze the substrate l-glutamine, which is of interest for medical proposes, since the glutaminase activity is usually related to adverse reaction during the leukemia treatment. This study showed that these new three non-recombinant l-asparaginases studied have potential application in the food and pharmaceutical industries, especially due to their good thermostability.

| S-EPMC6597663 | biostudies-literature

Mechanistic elucidation of monoalkyltin(iv)-catalyzed esterification.

Project description:Monoalkyltin(iv) complexes are well-known catalysts for esterification reactions and polyester formation, yet the mode of operation of these Lewis acidic complexes is still unknown. Here, we report on mechanistic studies of n-butylstannoic acid in stoichiometric and catalytic reactions, analyzed by NMR, IR and MS techniques. While the chemistry of n-butyltin(iv) carboxylates is dominated by formation of multinuclear tin assemblies, we found that under catalytically relevant conditions only monomeric n-BuSn(OAc)3 and dimeric (n-BuSnOAc2OEt)2 are present. Density functional theory (DFT) calculations provide support for a mononuclear mechanism, where n-BuSn(OAc)3 and dimeric (n-BuSnOAc2OEt)2 are regarded as off-cycle species, and suggest that carbon-oxygen bond breaking is the rate-determining step.

| S-EPMC8147323 | biostudies-literature

Halloysite-Catalyzed Esterification of Bio-Mass Derived Acids.

Project description:Halloysite, a natural clay with a hollow tubular structure, was studied as a catalyst for the esterification of biomass-derived carboxylic acids (levulinic acid, fumaric acid, maleic acid, and succinic acid) with four different alcohols (MeOH, EtOH, n-PrOH, and n-BuOH). Reaction conditions were optimized (10 mol % halloysite, 170 °C, 24 h) and gave high yields of the corresponding esters and diesters (>90%). The halloysite was easily recovered and recycled after washing and drying.

| S-EPMC6868903 | biostudies-literature

Kinetic Modeling of the Nickel-Catalyzed Esterification of Amides.

Project description:Nickel-catalyzed coupling reactions provide exciting tools in chemical synthesis. However, most methodologies in this area require high catalyst loadings, which commonly range from 10-20 mol % nickel. Through an academic-industrial collaboration, we demonstrate that kinetic modeling can be used strategically to overcome this problem, specifically within the context of the Ni-catalyzed conversion of amides to esters. The successful application of this methodology to a multigram-scale coupling, using only 0.4 mol % Ni, highlights the impact of this endeavor.

| S-EPMC5504487 | biostudies-literature

Alkali Halide Nanotubes: Structure and Stability.

Project description:Accurate density functional theory (DFT) and coupled-cluster (CCSD) calculations on a series of (LiF) n=2,36 neutral clusters suggest that nanotube structures with hexagonal and octagonal transversal cross sections show stability equal to or greater than that of the typical cubic form of large LiF crystals. The nanotube stability was further corroborated by quantum dynamic calculations at room temperature. The fact that stable nanotube structures were also found for other alkali halides (e.g., NaCl and KBr) suggests that this geometry may be widely implemented in material sciences.

| S-EPMC3873780 | biostudies-literature

Development of copper-catalyzed deaminative esterification using high-throughput experimentation.

Project description:Repurposing of amine and carboxylic acid building blocks provides an enormous opportunity to expand the accessible chemical space, because amine and acid feedstocks are typically low cost and available in high diversity. Herein, we report a copper-catalyzed deaminative esterification based on C-N activation of aryl amines via diazonium salt formation. The reaction was specifically designed to complement the popular amide coupling reaction. A chemoinformatic analysis of commercial building blocks demonstrates that by utilizing aryl amines, our method nearly doubles the available esterification chemical space compared to classic Fischer esterification with phenols. High-throughput experimentation in microliter reaction droplets was used to develop the reaction, along with classic scope studies, both of which demonstrated robust performance against hundreds of substrate pairs. Furthermore, we have demonstrated that this new esterification is suitable for late-stage diversification and for building-block repurposing to expand chemical space.

| S-EPMC9814592 | biostudies-literature

Sulfuric Acid Catalyzed Esterification of Amino Acids in Thin Film.

Project description:The esterification reaction of different amino acids with methanol catalyzed by H2SO4 was first studied in the small volume of thin films generated by ESI microdroplet deposition. The reaction is promoted by the pneumatic spray of the ESI source and reaches its maximum efficiency at a thin film temperature of 70 °C. Selective esterification of the COOH moiety was demonstrated. Microdroplet size and thin film volume and lifetime are critical parameters that influenced the reaction outcome. As expected, l-tyrosine and l-phenylalanine having aromatic side chain substituents were the most reactive amino acids, reaching absolute yields of around 40-50%. The amino acid esterification catalyzed by H2SO4 in a thin film occurs under synthetic conditions in which the same reaction in the bulk is not observed.

| S-EPMC10704590 | biostudies-literature

Optimized production, Pb(II) adsorption and characterization of alkali modified hydrochar from sugarcane bagasse.

Project description:Today, sugarcane bagasse (SB) is used for bioethanol and biodiesel production, energy generation, and adsorbent synthesis. The goal of this project is to determine the optimized conditions for producing adsorbent from sugarcane bagasse using hydrothermal carbonization (HTC) and KOH activation. To optimize process parameters such as reaction temperature, residence time, ZnCl2/SB mixing ratios, and water/SB mixing ratios, response surface methodology was used. The results revealed that the optimum modified adsorption occurred at 180 °C, 11.5 h, a water to biomass ratio of (5:1), and a ZnCl2 to precursor ratio of (3.5:1). The physicochemical features of optimum activated hydrochar were investigated, as well as batch adsorption experiments. The pseudo-second-order kinetic model and the Langmuir isotherm model were found to fit the experimental results in batch adsorption studies [[Formula: see text] (mg/g)]. Thermodynamic experiments further confirmed the spontaneous and exothermic adsorption mechanism.

| S-EPMC8595365 | biostudies-literature

Alumina-Doped Zirconia Submicro-Particles: Synthesis, Thermal Stability, and Microstructural Characterization.

Project description:Zirconia nanoceramics are interesting materials for numerous high-temperature applications. Because their beneficial properties are mainly governed by the crystal and microstructure, it is essential to understand and control these features. The use of co-stabilizing agents in the sol-gel synthesis of zirconia submicro-particles should provide an effective tool for adjusting the particles' size and shape. Furthermore, alumina-doping is expected to enhance the particles' size and shape persistence at high temperatures, similar to what is observed in corresponding bulk ceramics. Dispersed alumina should inhibit grain growth by forming diffusion barriers, additionally impeding the martensitic phase transformation in zirconia grains. Here, alumina-doped zirconia particles with sphere-like shape and average diameters of ? 300 n m were synthesized using a modified sol-gel route employing icosanoic acid and hydroxypropyl cellulose as stabilizing agents. The particles were annealed at temperatures between 800 and 1200 ? C and characterized by electron microscopy, elemental analysis, and X-ray diffraction. Complementary elemental analyses confirmed the precise control over the alumina content (0-50 mol%) in the final product. Annealed alumina-doped particles showed more pronounced shape persistence after annealing at 1000 ? C than undoped particles. Quantitative phase analyses revealed an increased stabilization of the tetragonal/cubic zirconia phase and a reduced grain growth with increasing alumina content. Elemental mapping indicated pronounced alumina segregation near the grain boundaries during annealing.

| S-EPMC6766039 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data