Condensation Of Acetaldehyde Research Articles

Chemoenzymatic Buta-1,3-diene Synthesis from Syngas Using Biological Decarboxylative Claisen Condensation and Zeolite-Based Dehydration.

A method for producing buta-1,3-diene (1,3-BD) by an amalgamation of chemical and biological approaches with syngas as the carbon source is proposed. Syngas is converted to the central intermediate, acetyl-CoA, by microorganisms through a tetrahydrofolate metabolism pathway. Acetyl-CoA is subsequently converted to malonyl-CoA using a carbonyl donor in the presence of a carboxylase enzyme. A decarboxylative Claisen condensation of malonyl-CoA and acetaldehyde ensues in the presence of acyltransferases to form 3-hydroxybutyryl-CoA, which is subsequently reduced by aldehyde reductase to give butane-1,3-diol (1,3-BDO). An ensuing dehydration step converts 1,3-BDO to 1,3-BD in the presence of a chemical dehydrating reagent.

Unraveling the reaction route and kinetics of 3‐methyl‐3‐penten‐2‐one synthesis for synthetic ketone fragrances

AbstractBACKGROUND3‐Methyl‐3‐penten‐2‐one (3M3P) is an indispensable raw material used for the synthesis of OTNE (octahydrotetramethyl acetophenone), a synthetic ketone fragrance known by commercial trade names, such as Iso E Super®, which is one of the most important ingredients in perfumes. This work is the first to unravel the reaction route and kinetics for the synthesis of 3M3P via the cross‐aldol condensation of acetaldehyde with butanone, catalyzed by the heterogeneous acidic ion exchange resin (NKC‐9).RESULTSAn effective method was developed to evaluate this complex reaction system: the reaction routes were determined experimentally from the product structures detected by Gas Chromatography Mass Spectrometry (GC‐MS), and the significance of side reactions were evaluated by the Yoneda group contribution method. The major side reactions are the self‐condensation of acetaldehyde (significant even under optimized reaction conditions) and the cross‐aldol condensation of acetaldehyde with 3M3P (which could be effectively suppressed at high butanone‐acetaldehyde molar ratio). The reaction kinetics was investigated at temperatures of 60–90 °C, catalyst mass fraction of 5 to 15%, and molar ratio of 5–20. At optimized reaction conditions, the yield of 3M3P was up to 90.85%, which is 2.4 times higher than that for the classic homogeneous catalysts (yield <38%).CONCLUSIONAcidic ion exchange resin NKC‐9 is a high‐selective green catalyst for the cross‐aldol condensation of acetaldehyde with butanone. Integrating experimental determination and thermomechanical analysis is an effective method to unravel the main reaction routes for a complex system. © 2020 Society of Chemical Industry (SCI)

Ethanol Conversion to Butadiene over Isolated Zinc and Yttrium Sites Grafted onto Dealuminated Beta Zeolite

Zinc and Yttrium single sites were introduced into the silanol nests of dealuminated BEA zeolite to produce Zn-DeAlBEA and Y-DeAlBEA. These materials were then investigated for the conversion of ethanol to 1,3-butadiene. Zn-DeAlBEA was found to be highly active for ethanol dehydrogenation to acetaldehyde and exhibited low activity for 1,3-butadiene generation. By contrast, Y-DeAlBEA was highly active for 1,3-butadiene formation but exhibited no activity for ethanol dehydrogenation. The formation of 1,3-butadine over Y-DeAlBEA and Zn-DeAlBEA does not occur via aldol condensation of acetaldehyde but, rather, by concerted reaction of coadsorbed acetaldehyde and ethanol. The active centers for this process are ≡Si-O-Y(OH)-O-Si≡ or ≡Si-O-Zn-O-Si-O≡ groups closely associated with adjacent silanol groups. The active sites in Y-DeAlBEA are 70 times more active than the Y sites supported on silica, for which the Y site is similar to that in Y-SiO2 but which lacks adjacent hydroxyl groups, and are 7 times more active than the active sites in Zn-DeAlBEA. We propose that C-C bond coupling in Y-DeAlBEA proceeds via the reaction of coadsorbed acetaldehyde and ethanol to form crotyl alcohol and water. The dehydration of crotyl alcohol to 1,3-butadiene is facile and occurs over the mildly Brønsted acidic ≡Si-OH groups present in the silanol nest of DeAlBEA. The catalysts reported here are notably more active than those previously reported for both the direct conversion of ethanol to 1,3-butadiene or the formation of this product by the reaction of ethanol and acetaldehyde.

Synthesis of crotonic acid from ethanol by sequential catalysis

Catalytic processes are important components of sustainable chemistry. We present a novel process to synthesize crotonic acid by sequential catalytic oxidation-condensation-oxidation reactions in a Soxhlet extractor. Oxidation of ethanol and crotonaldehyde is catalyzed by a new composite Cu/H3PO4 catalyst characterized by XRD (X-ray Diffraction), BET (Brunauer-Emmett-Teller analysis), TEM (Transmission Electron Microscopy), XPS (X-ray Photoelectron Spectrometry), and TG (Thermogravimetric analysis), showing higher activity and better stability compared to nano-copper, due to dispersion by a mutual support; external temperature compensation during the reaction allows ethanol oxidation without degradation of the catalyst. XRD and XPS analyses of the used catalyst reveal that monovalent copper is the active species for ethanol oxidation. The catalyst is effectively recovered and reused four times. Nano MgO catalyzes acetaldehyde condensation under mild conditions and can be recycled during the process. Conversion of ethanol is greater than 48%, and the selectivity to crotonic acid is 84% in the continuous process.

Havy Metal Cations Adsorption by Cinnamoyl C-methylcalix [4] Resorcinarene

Adsorption has been extensively studied as a costeffectivemethod for removing a wide variety of hazardous materials, such as dyes and heavy metals, from aqueous solutions. The aim of this research is to synthesized and applicated of CinnamoylC-methylcalix[4]resorcinarene (CCMCR) as the Cr(III) and Cd(II) adsorbent. The cinnamoyl C-metylcalix[4]resorcinarene was synthesized in 4 steps. They were synthesis of C-methylcalix[4]resorcinarene via acid-catalyzed condensation of resorcinol and acetaldehyde, followed by O-acetylation, Friedel-Craft cinnamoylation and hydrolysis. The characterization of the target compound was performed by IR and 1H-NMR. The adsorption of Cr(III) and Cd(II) was carried out in batch system. The effect of operating parameter conditions on capacity adsorption were investigated including acidity, interaction time, and the metal ion concentration. Most parameters in batch system confirm that CCMCR is a good adsorbent for Cr(III) but not good enough for Cd(II). The Cr(III) uptake was bigger than that of Cd(II), and also Cr(III) adsorption rate was faster than Cd(II). The adsorption kinetic both of Cr(III) and Cd(II) adsorptions in batch followed pseudo 2nd order kinetics model. It is mean that the adsorption process depend on concentration and the quantity of active site. The results of adsorption equilibirium study showed that in adsorption Cr(III) and Cd(II) onto CCMCR, Langmuir isoterm model was more applicable than Freundlich model.

Conversion of ethanol to 1,3–butadiene over Ag–ZrO2/SiO2 catalysts: The role of surface interfaces

Abstract A series of Ag–ZrO2/SiO2 catalysts with different metal–support interfaces were synthesized in an effort to elucidate the roles of specific interfaces in controlling the ethanol to 1,3–butadiene conversion and selectivity. According to the results of detailed characterizations (e.g. CO/pyridine–DRIFTS, XPS, TEM, NH3–TPD, and 1H MAS NMR), it was found that the Ag–O–Si interfaces significantly enhanced the dehydrogenation of ethanol while the presence of ZrO2 improved the interaction between Ag and ZrO2/SiO2, creating more Agδ+ active sites. The high dispersion of ZrO2 on SiO2 generated abundant Zr–O–Si interfaces with medium and weak Lewis acidity, promoting the condensation of acetaldehyde to crotonaldehyde. These Zr–O–Si interfaces in close interaction with Agδ+ species played a critical role in the enhanced H transfer during the MPV reduction of crotonaldehyde to crotyl alcohol. The synergies among the interfaces resulted in retarded ethanol dehydration reactivity, balanced ethanol dehydrogenation and condensation reactions, and a subsequent high 1,3–butadiene yield.

A Mathematical Model of the Synthesis of Pentaerythritol

Based on the results of a kinetic study of the condensation of acetaldehyde and formaldehyde in the presence of sodium hydroxide and taking into account well-known data, we compiled a reaction scheme of the process, in which pentaerythritol, dipentaerythritol, tripentaerythritol, bispentaerythritolformal, pentaerythritol methyl ether, and sodium 2,2-bis(hydroxymethyl)propanoate are formed. According to the reaction scheme, we developed a mathematical model of the process, which includes reaction rate equations and formulas for calculating the activity coefficients of ions and the degrees of ionization and equilibrium concentrations of intermediate substances. The effective kinetic parameters and activation energies of reactions were found. The adequacy of the mathematical model was statistically evaluated under the following conditions: an acetaldehyde–formaldehyde–sodium hydroxide molar ratio of 1 : 4–9 : 1.2, an initial acetaldehyde concentration of 0.4–0.9 mol/L, and a temperature of 13–47°C.

Synthesis of 23E-ethylidene spirostanes via the BF3·Et2O-catalyzed aldol condensation of steroid sapogenins and acetaldehyde

The treatment of acetylated steroid sapogenins with acetaldehyde and BF3·Et2O in CH2Cl2 led to moderate yields of the corresponding 23E-ethylidene spirostanes. The obtained compounds were characterized using a combination of 1D and 2D NMR techniques. Single crystal X-ray diffraction corroborated the proposed structures.

Enantioselective Aldol Addition of Acetaldehyde to Aromatic Aldehydes Catalyzed by Proline-Based Carboligases.

Aromatic β-hydroxyaldehydes, 1,3-diols, and α,β-unsaturated aldehydes are valuable precursors to biologically active natural products and drug molecules. Herein we report the biocatalytic aldol condensation of acetaldehyde with various aromatic aldehydes to give a number of aromatic α,β-unsaturated aldehydes using a previously engineered variant of 4-oxalocrotonate tautomerase [4-OT(M45T/F50A)] as carboligase. Moreover, an efficient one-pot two-step chemoenzymatic route toward chiral aromatic 1,3-diols has been developed. This one-pot chemoenzymatic strategy successfully combined a highly enantioselective aldol addition step catalyzed by a proline-based carboligase [4-OT(M45T/F50A) or TAUT015] with a chemical reduction step to convert enzymatically prepared aromatic β-hydroxyaldehydes into the corresponding 1,3-diols with high optical purity (e.r. up to >99:1) and in good isolated yield (51–92%). These developed (chemo)enzymatic methodologies offer alternative synthetic choices to prepare a variety of important drug precursors.

Rational engineering of 2-deoxyribose-5-phosphate aldolases for the biosynthesis of (R)-1,3-butanediol

Carbon-carbon bond formation is one of the most important reactions in biocatalysis and organic chemistry. In nature, aldolases catalyze the reversible stereoselective aldol addition between two carbonyl compounds, making them attractive catalysts for the synthesis of various chemicals. In this work, we identified several 2-deoxyribose-5-phosphate aldolases (DERAs) having acetaldehyde condensation activity, which can be used for the biosynthesis of (R)-1,3-butanediol (1,3BDO) in combination with aldo-keto reductases (AKRs). Enzymatic screening of 20 purified DERAs revealed the presence of significant acetaldehyde condensation activity in 12 of the enzymes, with the highest activities in BH1352 from Bacillus halodurans, TM1559 from Thermotoga maritima, and DeoC from Escherichia coli The crystal structures of BH1352 and TM1559 at 1.40-2.50 Å resolution are the first full-length DERA structures revealing the presence of the C-terminal Tyr (Tyr224 in BH1352). The results from structure-based site-directed mutagenesis of BH1352 indicated a key role for the catalytic Lys155 and other active-site residues in the 2-deoxyribose-5-phosphate cleavage and acetaldehyde condensation reactions. These experiments also revealed a 2.5-fold increase in acetaldehyde transformation to 1,3BDO (in combination with AKR) in the BH1352 F160Y and F160Y/M173I variants. The replacement of the WT BH1352 by the F160Y or F160Y/M173I variants in E. coli cells expressing the DERA + AKR pathway increased the production of 1,3BDO from glucose five and six times, respectively. Thus, our work provides detailed insights into the molecular mechanisms of substrate selectivity and activity of DERAs and identifies two DERA variants with enhanced activity for in vitro and in vivo 1,3BDO biosynthesis.

4-Chloro-2,6-Pyridinedicarboxylic Acid Functionalized Mesoporous Silica Nanocomposites for the Synthesis of Sinapaldehyde

4-Chloro-2,6-pyridinedicarboxylic acid (CPDA) functionalized mesoporous silica SBA-15 nanocomposites (SBA/5CPDA) were synthesized and characterized for the Knoevenagel condensation of syringaldehyde and acetaldehyde to synthesize sinapaldehyde in the liquid phase. The physicochemical characterization of the SBA/CPDA nanocomposites showed the decrease in the surface properties (surface area, pore size, pore volume) compared to SBA-15 confirming the complete functionalization of CPDA inside the mesopores of SBA-15 materials. The catalytic activity results displayed high activity (~90%) and selectivity (90–95%) of the desired product (sinapaldehyde) under environmental friendly conditions. All the reaction parameters were optimized to accomplish the maximum conversion of the selective products. Finally, the mechanism of the formation of the products was proposed and discussed.

1,3-Butadiene production from ethanol–water mixtures over Zn–La–Zr–Si oxide catalyst

Zn–La–Zr–Si oxide composition has been investigated in the ethanol-to-butadiene process using ethanol–water mixtures with different water content. An increase of H2O content in the initial reaction mixture decreases ethanol conversion, 1,3-butadiene selectivity, yield and productivity. The results of in situ FTIR spectroscopy (with ethanol and acetone as probe molecules) have shown the main reason for a decrease in activity of the catalyst to be H2O adsorption on active sites of aldol condensation of acetaldehyde and, to a lesser extent, ethanol dehydrogenation. Zn–La–Zr–Si oxide composition is a highly active and selective catalyst for the ethanol-to-butadiene process when ethanol–water mixture of 80 vol% ethanol and 20 vol% H2O is used, 60% 1,3-butadiene yield is achieved.

Catalytic Enhancement of Aldol Condensation by Oxygen Vacancy on CeO2 Catalysts

AbstractAldol condensation is a very useful reaction for biomass upgrading by coupling small molecule platform compounds into high value‐added products. Here we choose acetaldehyde (AcH) condensation, the rate‐determining step in bioethanol transformations, as a targeted reaction, and prepared four CeO2 catalysts with different concentrations of surface oxygen vacancies to investigate the role of oxygen vacancies in this reaction. To the best of our knowledge, it is the first time to demonstrate that there is a linear correlation between the activity of aldol condensation and the concentration of oxygen vacancies. Based on in‐situ FTIR studies, we conclude that oxygen vacancies are the Lewis acid sites for activation and stabilization of AcH, while lattice oxygen act as base sites for the formation of enolate species which are the key intermediates for AcH coupling reactions. Moreover, the proposed reaction mechanism indicates that Ce cations which are weak Lewis acid sites are not involved in the AcH condensation.

Insight into the effect of promoters (M = Cu, Ag, Zn, Zr) on aldol condensation reaction based on MgO surface in the process of ethanol to 1, 3-butadiene: A comparative DFT study

Based on density functional theory, the performance of aldol condensation of acetaldehyde to 3-hydroxybutanal on MgO surfaces doped with Cu/Ag/Zn/Zr was compared and analyzed, respectively. And the two kinds of coordination structures: terrace surface (Mg5C-O5C-T) and the kinks surface (Mg3C-O3C-K), were selected as the basis of MgO surface. Among these kinds of promoters, Zn and Ag have a little influence on the surface properties of MgO. While Cu and Zr could modify the acidity-basicity properties of MgO surfaces. Cu as the promoter could reduce the energy barrier of acetaldehyde enolization step on weak basicity site (Mg5C-O5C-T), and that of the proton back-transfer step on strong basic site (Mg3C-O3C-K) simultaneously. Moreover, Zr could promote both the formation of CC bond and proton back-transfer step on the strong basicity sites. It is speculated that strong basicity sites on MgO surface could be eliminated by the addition of Zr to avoid the excessive condensation of acetaldehyde, which could result in catalyst deactivation. In conclusion, Cu has a promoting effect on aldol condensation reaction on both two coordination structures of MgLC-OL'C ion pairs. Zr is beneficial to the performance of the strong basic catalyst.

Aldol condensation among acetaldehyde and ethanol reactants on TiO2: Experimental evidence for the kinetically relevant nucleophilic attack of enolates

Combinations of rate measurements as functions of reactant pressures, in situ infrared spectroscopy, comparisons of kinetic isotope effects, and rate inhibition effects provide experimental evidence that aldol condensation of acetaldehyde proceeds by kinetically relevant nucleophilic attack of a reactive enolate upon an acetaldehyde molecule over anatase TiO2. Steady-state turnover rates of aldol condensation measured as a function of the pressures of C2H4O, C2H5OH, H2O, and H2 between 503 K and 537 K show that rates reflect a second order dependence on C2H4O pressure and an inverse second order dependence on the C2H5OH pressure at the lowest C2H4O-to-C2H5OH ratios. Infrared spectra obtained in situ show that the exposed cationic Ti-atoms that facilitate aldol addition on TiO2 surfaces are saturated with C2H5OH∗ species and C2H4O∗ coverages are much smaller. In addition, aldol rates increase when C2D4O replaces C2H4O as a reactant, which likely reflects an inverse, secondary isotope effect caused by rehybridization of C-atoms at the transition state that forms a CC bond between two reactive intermediates derived from acetaldehyde. These results suggest that the kinetically relevant step is a bimolecular surface reaction, specifically the nucleophilic attack of an enolate onto a vicinal C2H4O∗ species. This conclusion is consistent also with aldol condensation rates that decrease with an inverse second order dependence on pyridine (C5H5N) pressure, because C5H5N displaces C2H4O from the two Lewis acid sites involved in the kinetically relevant step (confirmed by in situ FTIR). Comparisons to recent reports on the mechanism of this reaction on anatase TiO2 indicate that the presence of high coverages of C2H5OH∗ causes nucleophilic attack to become the kinetically relevant step by significantly reducing the number of enolate-acetaldehyde reactant pairs upon the surface.

Characterization of new flavan-3-ol derivatives in fermented cocoa beans

Two series of compounds showing mass signals at m/z 605 and 893 (negative ionization mode) have been detected in fermented cocoa beans. This study objective is to identify these mass signals and characterize their structure in fermented cocoa samples. Our hypothesis is that these signals may correspond to ethyl-bridged flavan-3-ols resulting from flavan-3-ol condensation with acetaldehyde which is a microbial metabolite. Mass spectrometry was used to compare the retention times and mass fragmentation patterns between a model solution using epicatechin and procyanidin dimer B2, the major flavan-3-ols of cocoa, as precursors and extracts of fermented cocoa. Their identification was confirmed: four isomers of ethyl-linked epicatechin as well as several isomers of epicatechin-ethyl-procyanidin B2, in which B2 was mostly linked through its upper unit, were characterized in cocoa. This study demonstrates the presence of flavan-3-ol acetaldehyde condensation products in fermented cocoa beans and provides the first report of epicatechin-ethyl-procyanidin B2.

Enzymatic Tandem Approach to Knoevenagel Condensation of Acetaldehyde with Acidic Methylene Compounds in Organic Media

A tandem enzyme‐catalyzed Knoevenagel reaction with acetaldehyde is presented. A new protocol for the synthesis of the desired products through a tandem process based on the enzymatic hydrolysis and Knoevenagel reaction starting from acetaldehyde precursors is disclosed. The influence of the reaction conditions including organic solvent, enzyme type, and temperature on the reaction course was tested. Further, this protocol was extended by subsequent tandem chemoenzymatic transformations leading to epoxides.

Synthesis and <i>In Vitro</i> Evaluation of C-methylcalix[4]resorcinaryl octacinnamate and C-methylcalix[4]resorcinaryl octabenzoate as the Sunscreen

The present study was aimed to synthesize and evaluate sunscreen activity of C-methylcalix[4]resorcinaryl octacinnamate and C-methylcalix[4]resorcinaryl octabenzoate. The target compounds were synthesized in 2 steps. They were a synthesis of C-methylcalix[4]-resorcinarene via acid catalyzed the condensation of resorcinol and acetaldehyde by using HCl catalyst, followed by esterification using cinnamoyl chloride and benzoyl chloride. The characterization of the target compounds was performed by IR, 1H-NMR, 13C-NMR, and LC-MS spectrometers. The sunscreen activity test was conducted by spectroscopic method and MTT-assay. Commercial sunscreen p-amino benzoic acid (PABA) was used as a comparator to the MTT assay. The sunscreen activity test used spectroscopic showed that C-methylcalix[4]resorcinaryl octacinnamate and C-methylcalix[4]resorcinaryl octabenzoate can absorb the ultraviolet radiation between 280 and 320 nm (UV-B) with the maximum absorption at 290 nm (ε = 31.535 M-1 cm-1) and 282 nm (ε = 42.217 M-1 cm-1), respectively. The results of MTT-assay indicated that the IC50 of C-methylcalix[4]resorcinaryl octacinnamate, C-methylcalix[4]resorcinaryl octabenzoate and PABA are 12.006, 20.568 and 12.564 ppm, respectively, it means that the order of sunscreen activity is C-methylcalix-[4]resorcinaryl octacinnamate, PABA and C-methylcalix[4]resorcinaryl octabenzoate.

Acetaldehyde as an ethanol derived bio-building block: an alternative to Guerbet chemistry

In this work, we describe a highly selective poly-aldol condensation of acetaldehyde, which can readily be obtained via dehydrogenation of ethanol.

Modelling the effects of reaction temperature and flow rate on the conversion of ethanol to 1,3-butadiene

A full factorial experimental design was performed to investigate the conversion of ethanol to 1,3-butadiene (1,3-BD), through manipulation of the reaction temperature and ethanol weight hourly space velocity. Reactions were carried out in presence of the catalyst K2O:ZrO2:ZnO/MgO-SiO2, prepared by co-precipitation methods. Mathematical models were developed to correlate observed product selectivities, 1,3-BD yields and productivities with the manipulated reaction variables, allowing for quantification of variable effects on catalyst activity and assessment of the kinetic mechanism. Obtained 1,3-BD productivities were as high as 0.5gBD/gcath,gBD/gcath, with 1,3-BD yields of 27%. Results suggest that acetaldehyde condensation is the rate determining step.