Hydrolysis Of Acetate Research Articles

Soft synthesis and characterization of goethite-based nanocomposites as promising cyclooctene oxidation catalysts.

Goethite based nanocomposites with a different composition such as 6FeO(OH)·MnO(OH)·0.5H2O (Mn-composite), xFeO(OH)·M(OH)2·yH2O (Co-composite (M: Co, x = 12, y = 3), Ni-composite (M: Ni, x = 7, y = 2)) and xFeO(OH)·MO·yH2O (Cu-composite (M: Cu, x = 5.5, y = 3), Zn-composite (M: Zn, x = 6, y = 1.5)) have been prepared by a soft chemical synthesis consisting in acetate hydrolysis. The data provided by Fourier transform infrared (FTIR), ultraviolet-visible-near infrared (UV-Vis-NIR), electron paramagnetic resonance (EPR) and Mössbauer spectra account for a slight modification of all composites' physicochemical properties compared to the starting material. Powder X-ray diffraction and transmission electron microscopy (TEM) investigations revealed the secondary phase nature and presence along with that of goethite. The TEM data are also consistent with a nano rod-like morphology with a 5–10 nm width and an average length of 40 nm. The catalytic oxidation of cyclooctene with O2 using isobutyraldehyde as reductant and acetonitrile as a solvent was performed in batch conditions for 5 h at room temperature. The selectivity for the epoxide was higher than 99% for all tested solids. The conversion of cyclooctene decreased from 55% to 4% following the same order of variance as the base/acid sites ratio: Mn-composite > Fe-composite > Co-composite > Ni-composite > Zn-composite > Cu-composite. The 6FeO(OH)·MnO(OH)·0.5H2O (Mn-composite) exhibited the most promising catalytic activity in cyclooctene oxidation, which can be correlated with the redox ability of Mn(iii) combined with the increased base character of this solid. The catalytic activity of this sample decreases by 10% after several successive reaction cycles.

Optimized Production of Xylooligosaccharides from Poplar: A Biorefinery Strategy with Sequential Acetic Acid/Sodium Acetate Hydrolysis Followed by Xylanase Hydrolysis

Optimized Production of Xylooligosaccharides from Poplar: A Biorefinery Strategy with Sequential Acetic Acid/Sodium Acetate Hydrolysis Followed by Xylanase Hydrolysis

Iron-catalyzed tandem oxidative coupling and acetal hydrolysis reaction to prepare formylated benzothiazoles and isoquinolines.

The aldehyde group is one of the most versatile intermediates in synthetic chemistry, and the introduction of an aldehyde group into heteroarenes is important for the transformation of molecular structure. Herein, we achieved the direct formylation of benzothiazo/les and isoquinolines. The reaction features a novel iron-catalyzed Minisci-type oxidative coupling process using commercially available 1,3-dioxolane as a formylated reagent followed by acetal hydrolysis without a separation process. The reaction can be performed under exceedingly mild reaction conditions and exhibits broad functional group tolerance.

Controllable enzymatic superactivity of α-chymotrypsin activated by the electrostatic interaction with cationic gemini surfactants.

Surfactant plays a critical role in enzymatic multi-functionalization processes. However, a deep understanding of surfactant-enzyme interactions has been lacking up until now due to the extreme complexity of the mixed system. This work reported the effect of cationic gemini surfactants, alkanediyl-α,ω-bis(dimethyldodecylammonium bromide) (C12CSC12Br2, S = 2, 6, and 10) on the enzymatic activity and conformation of α-chymotrypsin (α-CT) in phosphate buffer solution (PBS, pH 7.3). The enzymatic activity was assessed by the rate of 2-naphthyl acetate (2-NA) hydrolysis measured by UV-vis absorption. The superactivity of α-CT in the presence of C12CSC12Br2 appears in the concentration region below the critical micelle concentration (cmc) of the surfactant, and its maximum superactivity is correlated to the spacer length of C12CSC12Br2. Subtle regulation of the charge density of headgroups of the cationic surfactant can be achieved through partial charge neutralization of cationic headgroups by introducing inorganic counterions or oppositely charged surfactant, demonstrating that the electrostatic interaction plays the crucial role for emergence of the superactivity. The interaction between C12CSC12Br2 (S = 2,6, and 10) and α-CT was characterized by isothermal titration calorimetry (ITC), and the obtained endothermic enthalpy change indicates that the interaction induces the change in conformation and enzymatic superactivity. The methodologies of fluorescence spectroscopy, circular dichroism (CD), and differential scanning calorimetry (DSC) show that the gemini surfactants with different spacer lengths induct and regulate the secondary, tertiary and even fourth structures of the protein. The present work is significant to get deeper insight into the mechanism of the activation and denaturation of enzymes.

Greener and facile synthesis of Cu/ZnO catalysts for CO2 hydrogenation to methanol by urea hydrolysis of acetates.

Cu/ZnO-based catalysts for methanol synthesis by COx hydrogenation are widely prepared via co-precipitation of sodium carbonates and nitrate salts, which eventually produces a large amount of wastewater from the washing step to remove sodium (Na+) and/or nitrate (NO3−) residues. The step is inevitable since the remaining Na+ acts as a catalyst poison whereas leftover NO3− induces metal agglomeration during the calcination. In this study, sodium- and nitrate-free hydroxy-carbonate precursors were prepared via urea hydrolysis co-precipitation of acetate salt and compared with the case using nitrate salts. The Cu/ZnO catalysts derived from calcination of the washed and unwashed precursors show catalytic performance comparable to the commercial Cu/ZnO/Al2O3 catalyst in CO2 hydrogenation at 240–280 °C and 331 bar. By the combination of urea hydrolysis and the nitrate-free precipitants, the catalyst preparation is simpler with fewer steps, even without the need for a washing step and pH control, rendering the synthesis more sustainable.

Rotating bed reactor packed with heterofunctional structured silica-supported lipase. Developing an effective system for the organic solvent and aqueous phase reactions

Abstract Production of specialty chemicals increasingly makes use of the enzyme catalysts in organic solvents, and Novozym 435 (N435) is among most often applied. However, its polymeric skeleton is unstable in many solvents. In this context we report the results of a more systematic study of the biocatalysts, fabricated using highly porous siliceous pellets/enzyme carriers (MH, 4 cm3 g−1 total pore volume, 310 m2 g−1 surface area), grafted with octyl (-O), amino (-A) and octyl and amino (-OA) groups, to attach the enzyme - CALB lipase. The catalysts were deployed in a rotating bed reactor (RBR) and tested in hydrolysis of p-nitrophenyl acetate, and esterification of levulinic acid. Performance of the system was compared with the same RBR filled with N435. N435 appeared the most active in both reactions, when activity was related to bulk mass of the catalysts, mainly owing to very large enzyme load. But its pore structure degraded in many typical solvents already after 24 h of soaking, whereas no significant change in MH-O and MH-OA activity was detected. Irrespective of the solvent and reaction, the highest specific activity of the enzyme featured MH-O. However, a significant enzyme leaching from MH-O observed in a hydrolytic reaction, in stark contrast to MH-OA which came second in specific activity, point to MH-OA as the catalyst of choice for hydrolytic reactions. In esterification reaction the MH-O lipase was not only most active but it was also quite stable. Therefore, MH-O appears the most suitable production system for the reactions carried out in organic solvents.

Theoretical study of the side reactions of the catalytic conversion of ethanol to butadiene on metal oxide catalysts

Side reactions of the ethanol-to-butadiene conversion catalyzed by MgO or ZnO were analyzed by density functional theory. We examined acetaldehyde disproportion to generate ethyl acetate, the hydrolysis of ethyl acetate to acetic acid, and the ketonization of acetic acid to generate acetone and CO2. The reactivities of these reactions on MgO and ZnO were compared. Our results revealed that among the three reactions, the difference in reactivity between the two oxides was greatest for the ketonization reaction—there was a higher activation barrier on MgO than on ZnO. This would cause the higher ratio of by-products on ZnO than on MgO.

A De Novo Designed Esterase with p-Nitrophenyl Acetate Hydrolysis Activity

Esterases are a large family of enzymes with wide applications in the industry. However, all esterases originated from natural sources, limiting their use in harsh environments or newly- emerged reactions. In this study, we designed a new esterase to develop a new protocol to satisfy the needs for better biocatalysts. The ideal spatial conformation of the serine catalytic triad and the oxygen anion hole at the substrate-binding site was constructed by quantum mechanical calculation. The catalytic triad and oxygen anion holes were then embedded in the protein scaffold using the new enzyme protocol in Rosetta 3. The design results were subsequently evaluated, and optimized designs were used for expression and purification. The designed esterase had significant lytic activities towards p-nitrophenyl acetate, which was confirmed by point mutations. Thus, this study developed a new protocol to obtain novel enzymes that may be useful in unforgiving environments or novel reactions.

Exergy, economic and environmental assessment of sec-butyl acetate hydrolysis to sec-butyl alcohol using a combined reaction and extractive distillation system

Sec-butyl alcohol (SBA), an important chemical intermediate, is widely used in the synthesis of methyl ethyl ketone, herbicides and other products. However, there are some problems, such as high energy consumption and high equipment investment, in the traditional method of SBA production. With the mature application of the synthesis method of sec-butyl acetate (SBAC) in industry, the excess capacity of SBAC gradually appears. The synthesis of SBA from SBAC has become a research hotspot. SBA synthesized via the hydrolysis of SBAC has the advantages of fewer byproducts and wide sources of raw materials, but it has the limitation of a low degree of hydrolysis. In this study, based on Douglas’s economic optimization model, taking the total annual cost (TAC) as the objective function, the influencing factors and suitable operating conditions of the SBAC hydrolysis reactive extractive distillation process were explored, and TAC was obtained under the optimal operating conditions. The environmental performance of the process was studied according to life cycle analysis. The exergy efficiency was obtained based on thermodynamic analysis. The process was analyzed from the aspects of exergy, environment and economy, which provided theoretical guidance for the industrial design of the new SBA process.

Fabrication of zinc/silver binary nanoparticles, their enhanced microbial and adsorbing properties

Monometallic ZnO nanoparticles were prepared by hydrolysis of zinc acetate with ammonium hydroxide solution. Bimetallic zinc-silver nanoparticles (ZnO-AgNPs) were prepared using metal displacement galvanic cell reaction in presence of cetyltrimethylammonium bromide (CTAB). The optical and photo-physical properties of both NPs were determined. Surface plasmon resonance (SPR) intensity of ZnO-AgNPs depends on the ratio of metal salt precursors and other experimental conditions. The optical band gap (2.98 eV), agglomeration number (26819.92), and molar concentration (1.14 × 10−4 mol/liter) of ZnO-AgNPs were determined. Langmuir adsorption monolayer, Freundlich, intraparticles diffusion and multilayer adsorption isotherms used for the determination of maximum adsorption efficiency and adsorption isotherm parameters to the removal of safranin dye from an aqueous solution. The kinetics of safranin removal has also been discussed with pseudo-first order, pseudo-second order, intraparticle diffusion and multilayer kinetic models. The antibacterial and antifungal activities of ZnO, Ag and ZnO-AgNPs were determined against human pathogens using growth kinetic and disk diffusion methods. The concentrations of ZnO-AgNPs have significant effect on the bacterial growth kinetics. The death rate constants increase with increasing the NPs concentrations. It has been found that the ZnO-AgNPs hold higher microbial activities than that of monometallic counterpart, ZnO and AgNPs. Mechanism of bacterial growth and death was discussed.

Exploration of Acetylation as a Base-Labile Protecting Group in Escherichia coli for an Indigo Precursor.

Biochemical protecting groups are observed in natural metabolic pathways to control reactivity and properties of chemical intermediates; similarly, they hold promise as a tool for metabolic engineers to achieve the same goals. Protecting groups come with costs: lower yields from carbon, metabolic load to the production host, deprotection catalyst costs and kinetics limitations, and wastewater treatment of the group. Compared to glycosyl biochemical protection, such as glucosyl groups, acetylation can mitigate each of these costs. As an example application where these benefits could be valuable, we explored acetylation protection of indoxyl, the reactive precursor to the clothing dye, indigo. First, we demonstrated denim dyeing with chemically sourced indoxyl acetate by deprotection with base, showing results comparable to industry-standard denim dyeing. Second, we modified an Escherichia coli production host for improved indoxyl acetate stability by the knockout of 14 endogenous hydrolases. Cumulatively, these knockouts yielded a 67% reduction in the indoxyl acetate hydrolysis rate from 0.22 mmol/g DCW/h to 0.07 mmol/g DCW/h. To biosynthesize indoxyl acetate, we identified three promiscuous acetyltransferases which acetylate indoxyl in vivo. Indoxyl acetate titer, while low, was improved 50%, from 43 μM to 67 μM, in the hydrolase knockout strain compared to wild-type E. coli. Unfortunately, low millimolar concentrations of indoxyl acetate proved to be toxic to the E. coli production host; however, the principle of acetylation as a readily cleavable and low impact biochemical protecting group and the engineered hydrolase knockout production host should prove useful for other metabolic products.

Synthesis and Biological Evaluation of a Carbamate-Containing Tubulysin Antibody-Drug Conjugate.

Antibody-drug conjugates (ADCs) use antibodies to deliver cytotoxic payloads directly into tumor cells via specifically binding to the target cell surface antigens. ADCs can enhance the anti-tumor effects of antibodies, and increase the delivery of cytotoxic payloads to cancer cells with a better therapeutic index. An ADC was prepared with a potent carbamate-containing tubulysin analogue attached to an anti-mesothelin antibody via a Cit-Val dipeptide linker. An aniline functionality in the tubulysin analogue was created to provide a site of linker attachment via an amide bond that would be stable in systemic circulation. Upon ADC internalization into antigen-positive cancer cells, the Cit-Val dipeptide linker was cleaved by lysosomal proteases, and the drug was released inside the tumor cells. The naturally occurring acetate of tubulysin was modified to a carbamate to reduce acetate hydrolysis of the ADC in circulation and to increase the hydrophilicity of the drug. The ADC bearing the monoclonal anti-mesothelin antibody and the carbamate-containing tubulysin was highly potent and immunologically specific to H226 human lung carcinoma cells in vitro, and efficacious at well-tolerated doses in a mesothelin-positive OVCAR3 ovarian cancer xenograft mouse model.

Large-Scale Synthesis of 2-Chlorotetrahydroquinoline and 2-Chlorotetrahydroquinolin-8-one

An efficient large-scale preparation of 2-chlorotetrahydroquinoline with cyclohexanone and benzylamine as starting materials was developed and well optimized, in which benzyl-protected enamide was successfully cyclized and benzyl group was directly removed under Vilsmeier conditions. Azeotropic distillation provided 264 g of 2-chlorotetrahydroquinoline (79%) on a 2 mol scale of reaction without intermediate isolation. The downstream product 2-chlorotetrahydroquinolin-8-one was acquired through Boekelheide rearrangement, hydrolysis of acetate via NaBH4 reduction, and Anelli oxidation. With the developed procedure, the intermediates were not necessary to be isolated and 2-chlorotetrahydroquinolin-8-one was conveniently obtained with solvent slurry in 65% overall isolated yield in a four-step sequence.

Investigating differences and similarities between two new abiraterone polymorphs and its hydrochloride salt monohydrate

Crystal and molecular structures of two polymorphs (forms II and III) of abiraterone are presented. Both crystal modifications crystallize in the monoclinic crystal system P21 with one molecule in the asymmetric unit. Molecules are involved in strong and weak intermolecular hydrogen bonds of O-H⋅⋅⋅N and C-H⋅⋅⋅O types. Differences in crystals packing and intermolecular interactions were demonstrated by the Hirshfeld surface analysis.The spectroscopic studies showed the correlation of O⋅⋅⋅N distances with wavenumbers of OH groups for abiraterone polymorphs. The IR results agree with a density rule for form III suggesting that this form has a lower thermodynamic stability at 0 K.Abiraterone hydrochloride monohydrate is a direct product of abiraterone acetate hydrolysis under acidic conditions. The salt is unstable during crystallization and transforms into abiraterone base. The detailed description of hydrogen bonds and the analysis of main intermolecular contacts to the Hirshfeld surface of the salt measured at 100 K are presented.

Fluorogenic Probe Using a Mislow–Evans Rearrangement for Real‐Time Imaging of Hydrogen Peroxide

AbstractHydrogen peroxide (H2O2) mediates the biology of wound healing, apoptosis, inflammation, etc. H2O2 has been fluorometrically imaged with protein‐ or small‐molecule‐based probes. However, only protein‐based probes have afforded temporal insights within seconds. Small‐molecule‐based electrophilic probes for H2O2 require many minutes for a sufficient response in biological systems. Here, we report a fluorogenic probe that selectively undergoes a [2,3]‐sigmatropic rearrangement (seleno‐Mislow‐Evans rearrangement) with H2O2, followed by acetal hydrolysis, to produce a green fluorescent molecule in seconds. Unlike other electrophilic probes, the current probe acts as a nucleophile. The fast kinetics enabled real‐time imaging of H2O2 produced in endothelial cells in 8 seconds (much earlier than previously shown) and H2O2 in a zebrafish wound healing model. This work may provide a platform for endogenous H2O2 detection in real time with chemical probes.

Fluorogenic Probe Using a Mislow-Evans Rearrangement for Real-Time Imaging of Hydrogen Peroxide.

Hydrogen peroxide (H2 O2 ) mediates the biology of wound healing, apoptosis, inflammation, etc. H2 O2 has been fluorometrically imaged with protein- or small-molecule-based probes. However, only protein-based probes have afforded temporal insights within seconds. Small-molecule-based electrophilic probes for H2 O2 require many minutes for a sufficient response in biological systems. Here, we report a fluorogenic probe that selectively undergoes a [2,3]-sigmatropic rearrangement (seleno-Mislow-Evans rearrangement) with H2 O2 , followed by acetal hydrolysis, to produce a green fluorescent molecule in seconds. Unlike other electrophilic probes, the current probe acts as a nucleophile. The fast kinetics enabled real-time imaging of H2 O2 produced in endothelial cells in 8 seconds (much earlier than previously shown) and H2 O2 in a zebrafish wound healing model. This work may provide a platform for endogenous H2 O2 detection in real time with chemical probes.

Potent double prodrug forms of synthetic phosphoantigens

Phosphoantigens are ligands of BTN3A1 that stimulate anti-cancer functions of γδ T cells, yet the potency of natural phosphoantigens is limited by low cell permeability and low metabolic stability. Derivatives of BTN3A1 ligand prodrugs were synthesized that contain an acetate-protected allylic alcohol and act as doubly protected prodrugs. A novel set of phosphonates, phosphoramidates, and phosphonamidates has been prepared through a new route that simplifies synthesis and postpones the point of divergence into different prodrug forms. One of the new prodrugs, compound 11, potently stimulates γδ T cell proliferation (72 h EC50 = 0.12 nM) and interferon γ response to loaded leukemia cells (4 h EC50 = 19 nM). This phosphonamidate form was > 900x more potent than the corresponding phosphoramidate, and the phosphonamidate form was also significantly more stable in plasma following acetate hydrolysis. Therefore, prodrug modification of phosphonate butyrophilin ligands at the allylic alcohol can both facilitate chemical synthesis and improve potency of γδ T cell stimulation.

Modulation of lipase B from Candida antarctica properties via covalent immobilization on eco-friendly support for enzymatic kinetic resolution of rac-indanyl acetate.

In this study, the modulation of enzymatic biocatalysts were developed by the use of lipase B from Candida antarctica covalently immobilized on an eco-friendly support, cashew apple bagasse, activated with 10% glycidol-ethylenediamine-glutaraldehyde (GEG) under different immobilization strategies (5mM or 100mM ionic strength and in absence or presence of 0.5% (v/v) Triton X-100). The biocatalysts were characterized for thermal and organic solvents stabilities and compared with the soluble enzyme. The biocatalysts were then applied to the hydrolysis of the rac-indanyl acetate (2:1 ratio enzyme/substrate) at pH 7.0 and 30°C for 24h. For all the strategies evaluated, GEG promoted kinetic resolution of rac-indanyl acetate with maximum conversion (50%) and led to (R)-indanol with excellent enantiomeric excess (97%), maintaining the maximum conversion for five consecutive cycles of hydrolysis. Therefore, the use of cashew apple bagasse has proved to be a promising eco-friendly support for enzyme immobilization, since it resulted in stable biocatalysts for enzymatic kinetic resolution.

Honeycomb-structured solid acid catalysts fabricated via the swelling-induced self-assembly of acidic poly(ionic liquid)s for highly efficient hydrolysis reactions

The development of heterogeneous acid catalysts with higher activity than homogeneous acid catalysts is critical and still challenging. In this study, acidic poly(ionic liquid)s with swelling ability (SAPILs) were designed and synthesized via the free radical copolymerization of ionic liquid monomers, sodium p-styrenesulfonate, and crosslinkers, followed by acidification. The 31P nuclear magnetic resonance chemical shifts of adsorbed trimethylphosphine oxide indicated that the synthesized SAPILs presented moderate and single acid strength. The thermogravimetric analysis results in the temperature range of 300–345 °C revealed that the synthesized SAPILs were more stable than the commercial resin Amberlite IR-120(H) (245 °C). Cryogenic scanning electron microscopy testing demonstrated that SAPILs presented unique three-dimensional (3D) honeycomb structure in water, which was ascribed to the swelling-induced self-assembly of the molecules. Moreover, we used SAPILs with micron-sized honeycomb structure in water as catalysts for the hydrolysis of cyclohexyl acetate to cyclohexanol, and determined that their catalytic activity was much higher than that of homogeneous acid catalysts. The equilibrium concentrations of all reaction components inside and outside the synthesized SAPILs were quantitatively analyzed using a series of simulated reaction mixtures. Depending on the reaction mixture, the concentration of cyclohexyl acetate inside SAPIL-1 was 7.5–23.3 times higher than that outside of it, which suggested the high enrichment ability of SAPILs for cyclohexyl acetate. The excellent catalytic performance of SAPILs was attributed to their 3D honeycomb structure in water and high enrichment ability for cyclohexyl acetate, which opened up new avenues for designing highly efficient heterogeneous acid catalysts that could eventually replace conventional homogeneous acid catalysts.

Temperature gradient and pH effects on Sor estimates from SWCT tests - The no buffer case

Residual oil saturation (Sor) is the fraction of immobile oil that remains after a water flood. This information is important for calculating recoverable reserves and evaluating EOR campaigns. Single Well Chemical Tracer (SWCT) tests yield a near-well average Sor based on a large rock volume. Correctly performed and analyzed, SWCT tests yield reliable Sor estimates. There are, however, two important effects that commonly are ignored. One is cooling of the reservoir during injection of the cold brine resulting in decreased hydrolysis rate of the primary tracer. The other is the hydrolysis rate's pH dependence. To study these phenomena, we have developed a numerical model of an ethyl acetate SWCT test and applied it to a generic case with test and formation data based on published values. An analytical model is used to calculate how the brine injection temperature varies with time. The ethyl acetate hydrolyses into ethanol and acetic acid that lowers the pH and changes the hydrolysis rate. Any buffer capacity in the injected fluid or formation is neglected. Our model is the first ever to combine realistic temperature calculations with pH dependent ethyl acetate hydrolysis rate during a SWCT test. Sor is estimated from synthetic tracer production curves using the direct chromatographic separation equation as well as the mean residence time. A large number of simulations were performed to investigate how the Sor estimates vary with different model assumptions and input data. In all cases, both methods underestimate the true Sor, typically by 2–4% - in some cases significantly more. We demonstrate that neglecting dispersion in the wellbore during injection and production is warranted with the rock and test data used in this study.