Vinyl Esters Research Articles

High- and low-temperature ignition delay time study and modeling efforts on vinyl acetate

Although esters in general have received much attention over the last decade of combustion research, the combustion of vinyl esters have yet not been studied in detail. Recent studies on ethyl acetate show that vinyl acetate is a major intermediate but its combustion is not well understood. This may be due to the fact that vinyl acetate itself can presumably not be used as a fuel or fuel additive, but both the fundamental understanding of vinyl ester combustion and the improvement of the ethyl ester modeling motivate the present study. Building on the work on ethyl acetate, a first kinetic model for the high- and low-temperature combustion of vinyl acetate is proposed, which includes reactions and intermediates that have not been considered before. These reactions are based on low-level quantum mechanical calculations as well as analogies drawn to mainly ethyl acetate. Seven additional species are considered compared to the ethyl acetate study for which the thermochemical data is derived by ab-initio calculations. The vinyl acetate kinetic model is validated against ignition delay times obtained in a shock tube and a rapid compression machine at pressures of 20 and 40 bar and temperatures ranging from 850 to 1250 K. Overall, a satisfactory agreement between the predictions of the kinetic model and the experimental data was found for all investigated conditions. Rate of production and brute force sensitivity analyses were performed to identify the most relevant reaction pathways, which underline the strong connection between the vinyl acetate and ethyl acetate chemistry.

The Synthesis and Evaluation of Diethyl Benzylphosphonates as Potential Antimicrobial Agents.

The impact of substituent at phenyl ring of diethyl benzylphosphonate derivatives on cytotoxic activity was studied. The organophosphonates were obtained based on developed palladium-catalyzed α, β-homodiarylation of vinyl esters protocol. The new synthetic pathway toward 1,2-bis(4-((diethoxyphosphoryl)methyl)phenyl)ethyl acetate was proposed which significantly improves the overall yield of the final product (from 1% to 38%). Several newly synthesized organophosphonates were tested as new potential antimicrobial drugs on model Escherichia coli bacterial strains (K12 and R2-R3). All tested compounds show the highest selectivity and activity against K12 and R2 strains. Preliminary cellular studies using MIC and MBC tests and digestion of Fpg after modification of bacterial DNA suggest that selected benzylphosphonate derivatives may have greater potential as antibacterial agents than typically used antibiotics such as ciprofloxacin, bleomycin and cloxacillin. These compounds are highly specific for pathogenic E. coli strains based on the model strains used and may be engaged in the future as new substitutes for commonly used antibiotics, which is especially important due to the increasing resistance of bacteria to various drugs and antibiotics.

Modification of nanocellulose films in deep eutectic solvents using vinyl esters

The hydrophilicity of nanocellulose materials mitigates their good mechanical and oxygen barrier properties when exposed to humid conditions. It also limits nanocellulose use in many applications where water is present. This study reveals hydrophobic modification of cellulose nanofiber (CNF) films with vinyl esters of variable alkyl chain length using deep eutectic solvent (DES) of imidazole and triethylmethylammonium chloride as a reaction medium. Additionally, the influence of ultraviolet-ozone (UV/O3) pretreatment on CNF film modification in DES was addressed. The esterification of CNF films in DES was proven to be a simple and fast approach to increase the hydrophobicity of the films (increasing the contact angle from 38° to 107°), requiring only a 15 min reaction time and reaction temperature of 80 °C. Moreover, the modification improved water vapor barrier properties of the films and resulted in improved mechanical properties at wet state, especially with films treated with UV and ozone before modification.

Synthesis of 13 C and 2 H Labeled Vinyl Pyruvate and Hyperpolarization of Pyruvate.

The hyperpolarization of nuclear spins has enabled unique applications in chemistry, biophysics, and particularly metabolic imaging. Parahydrogen-induced polarization (PHIP) offers a fast and cost-efficient way of hyperpolarization. Nevertheless, PHIP lags behind dynamic nuclear polarization (DNP), which is already being evaluated in clinical studies. This shortcoming is mainly due to problems in the synthesis of the corresponding PHIP precursor molecules. The most widely used DNP tracer in clinical studies, particularly for the detection of prostate cancer, is 1-13 C-pyruvate. The ideal derivative for PHIP is the deuterated vinyl ester because the spin physics allows for 100 % polarization. Unfortunately, there is no efficient synthesis for vinyl esters of β-ketocarboxylic acids in general and pyruvate in particular. Here, we present an efficient new method for the preparation of vinyl esters, including 13 C labeled, fully deuterated vinyl pyruvate using a palladium-catalyzed procedure. Using 50 % enriched parahydrogen and mild reaction conditions, a 13 C polarization of 12 % was readily achieved; 36 % are expected with 100 % pH2 . Higher polarization values can be potentially achieved with optimized reaction conditions.

Investigation on mechanical, morphological, and water absorption of coconut particles/nanoclay–reinforced vinyl esters hybrid bio-nanocomposites

Investigation on mechanical, morphological, and water absorption of coconut particles/nanoclay–reinforced vinyl esters hybrid bio-nanocomposites

Regioselective Dearomatization of N‐Alkylquinolinium and Pyridinium Salts under Morita‐Baylis‐Hillman Conditions

AbstractMorita‐Baylis‐Hillman reaction employing N‐alkylquinolinium salts as electrophiles has been developed. The reaction is promoted by DBU, which acts both as a catalyst activating the electron‐poor olefin as well as a base. The dearomatization occurs regioselectively at the C‐2 position, delivering a broad range of α‐(1,2‐dihydroquinolin‐2‐yl)vinyl esters, ketones, and sulfones. The scope of the transformation has also been extended to N‐alkylpyridinium salts. For this class of substrates a presence of at least moderately electron‐withdrawing substituent in the ring is necessary to attain good reactivity. In particular, N‐alkylpyridinium salts containing an ester group undergo the dearomatization regioselectively at the C‐4 position, while nitrile and nitro moieties cause the non‐selective formation of products of the C‐2 and C‐6 additions.magnified image

Biocatalytic hydrolysis of various esters using Baker’s yeast under neutral conditions without sucrose

We have found that biocatalytic hydrolysis of various esters using Baker’s yeast proceeds efficiently under neutral conditions without sucrose. Hydrolysis of ethyl, methyl, propyl, isopropyl, benzyl, allyl, prenyl, and vinyl esters of 3-phenylpropanoic acid using Baker’s yeast gave easily 3-phenylpropanoic acid in 52–86% yields. In contrast, Baker’s yeast did not hydrolyze the rigid structural esters such as cinnamyl and phenyl 3-phenylpropanoates. Then, Baker’s yeast hydrolyzed various ethyl esters of 3-arylpropanoic acids, 4-phenylbutanoic acid, and fatty acids to afford the corresponding acids in 29–85% yields.

Engineering silica encapsulated composite of acyltransferase from Mycobacterium smegmatis and MIL-88A: A stability-and activity-improved biocatalyst for N-acylation reactions in water

Here the metal-organic framework material MIL-88A is used to purify and immobilize an acyltransferase from Mycobacterium smegmatis (MsAcT) simultaneously from the broken bacterial liquid. Regarding the possibility that the MsAcT@MIL-88A may display weak stability in its application, a silica layer is further introduced around it as a “shield” to protect the enzyme from degradation. The obtained MsAcT@MIL-88A@silica can exhibit high activity recovery, excellent thermal, pH, and storage stabilities compared with those of MsAcT@MIL-88A. The MsAcT@MIL-88A@silica can also be effectively recycled, and its initial activity of 84.0 % ± 1.2 % can be retained after the 5th cycle for N-acylation reaction in water. More importantly, the MsAcT@MIL-88A@silica can display much higher catalytic activity towards the reactions between ethyl or vinyl esters and aniline than those of free MsAcT and MsAcT@MIL-88A in aqueous media. This study provides a simple and inexpensive strategy to prepare MsAcT@MIL-88A@silica with high activity, stability, and excellent recyclability, and highlights its application potential as a biocatalyst.

Chromium-Catalyzed Selective Borylation of Vinyl Triflates and Unactivated Aryl Carboxylic Esters with Pinacolborane.

The use of pinacolborane to borylate abundant vinyl triflates and unactivated aryl carboxylic esters was enabled by chromium catalysis via the selective formation of vinyl and aryl boronate esters. The competing hydrided reduction or allylic borylation proceeds sluggishly or does not occur, therefore providing a selective strategy for the incorporation of boronate into olefins and arenes. Mechanistic studies indicate that the σ-bond metathesis or oxidative addition mechanism may be considered to be responsible for the cleavage of ester scaffolds.

Promiscuous Lipase-Catalyzed Markovnikov Addition of H-Phosphites to Vinyl Esters for the Synthesis of Cytotoxic α-Acyloxy Phosphonate Derivatives.

An enzymatic route for phosphorous-carbon- bond formation is developed by discovering new promiscuous activity of lipase. This biocatalytic transformation of phosphorous-carbon- bond addition leads to biologically and pharmacologically relevant α-acyloxy phosphonates with methyl group in α-position. A series of target compounds were synthesized with yields ranging from 54% to 83% by enzymatic reaction with Candida cylindracea (CcL) lipase via Markovnikov addition of H-phosphites to vinyl esters. We carefully analyzed the best conditions for the given reaction such as the type of enzyme, temperature, and type of solvent. The developed protocol is applicable to a range of H-phosphites and vinyl esters significantly simplifying the preparation of synthetically challenging α-pivaloyloxy phosphonates. Further, the obtained compounds were validated as new potential antimicrobial drugs with characteristic E. coli bacterial strains and DNA modification recognized by the Fpg protein, N-methyl purine glycosylases as new substrates. The impact of the methyl group located in the α-position of the studied α-acyloxy phosphonates on the antimicrobial activity was demonstrated. The pivotal role of this group on inhibitory activity against selected pathogenic E. coli strains was revealed. The observed results are especially important in the case of the increasing resistance of bacteria to various drugs and antibiotics.

Enzymatic Synthesis and Molecular Modelling Studies of Rhamnose Esters Using Lipase from Pseudomonas stutzeri.

Rhamnolipids are becoming an important class of glycolipid biosurfactants. Herein, we describe for the first time the enzymatic synthesis of rhamnose fatty acid esters by the transesterification of rhamnose with fatty acid vinyl esters, using lipase from Pseudomonas stutzeri as a biocatalyst. The use of this lipase allows excellent catalytic activity in the synthesis of 4-O-acylrhamnose (99% conversion and full regioselectivity) after 3 h of reaction using tetrahydrofuran (THF) as the reaction media and an excess of vinyl laurate as the acyl donor. The role of reaction conditions, such as temperature, the substrates molar ratio, organic reaction medium and acyl donor chain-length, was studied. Optimum conditions were found using 35 °C, a molar ratio of 1:3 (rhamnose:acyldonor), solvents with a low logP value, and fatty acids with chain lengths from C4 to C18 as acyl donors. In hydrophilic solvents such as THF and acetone, conversions of up to 99–92% were achieved after 3 h of reaction. In a more sustainable solvent such as 2-methyl-THF (2-MeTHF), high conversions were also obtained (86%). Short and medium chain acyl donors (C4–C10) allowed maximum conversions after 3 h, and long chain acyl donors (C12–C18) required longer reactions (5 h) to get 99% conversions. Furthermore, scaled up reactions are feasible without losing catalytic action and regioselectivity. In order to explain enzyme regioselectivity and its ability to accommodate ester chains of different lengths, homology modelling, docking studies and molecular dynamic simulations were performed to explain the behaviour observed.

Gamma Radiation- and Ultraviolet-Induced Polymerization of Bis(amino acid)fumaramide Gel Assemblies.

Controlling the polymerization of supramolecular self-assembly through external stimuli holds great potential for the development of responsive soft materials and manipulation at the nanoscale. Vinyl esters of bis(leu or val)fumaramide (1a and 2a) have been found to be gelators of various organic solvents and were applied in this investigation of the influence of organogelators’ self-assembly on solid-state polymerization induced by gamma and ultraviolet irradiation. Here, we report our investigation into the influences of self-assemblies of bis(amino acid vinyl ester)fumaramides on gamma-ray- and ultraviolet-induced polymerization. The gelator molecules self-assembled by non-covalent interactions, mainly through hydrogen bonds between the amide group (CONH) and the carboxyl group (COO), thus forming a gel network. NMR and FTIR spectroscopy were used to investigate and characterize supramolecular gels. TEM and SEM microscopy were used to investigate the morphology of gels and polymers. Morphology studies showed that the gels contained a filamentous structure of nanometer dimensions that was exhaustive in a three-dimensional network. The prepared derivatives contained reactive alkyl groups suitable for carrying out the polymerization reaction initiated by gamma or ultraviolet radiation in the supramolecular aggregates of selected gels. It was found that the polymerization reaction occurred only in the network of the gel and was dependent on the structure of aggregates or the proximity and orientation of double bonds in the gel network. Polymers were formed by the gels exposure to gamma and ultraviolet radiation in toluene, and water/DMF gels with transcripts of their gel structure into polymers. The polymeric material was able to immobilize various solvents by swelling. Furthermore, methyl esters of bis(leu and val)fumaramide (1b and 2b) were synthesized; these compounds showed no gelling properties, and the crystal structure of the valine derivative 2b was determined.

ExxonMobil buys resin firm Materia

ExxonMobil Chemical has acquired Materia, a company formed by California Institute of Technology professor Robert Grubbs to make thermoset resins using the science for which he won the 2005 Nobel Prize in Chemistry. Materia uses ruthenium catalysts to carry out olefin metathesis, a customizable reaction that breaks carbon-carbon double bonds and forms new ones. The firms say Materia’s materials are lighter, stronger, and more durable than epoxies, vinyl esters, and polyesters.

Enzymatic modification of enriched lemon oil in a solvent-free reaction medium: Bioconversion yield and product profile

The present study focused on the modification of the chemical profile of selected terpenes and enriched lemon essential oil through lipase-catalyzed transesterification with the aim to broaden their applications. The reaction capacities of 3 terpenes (eugenol, thymol, geraniol) with vinyl esters (vinyl acetate, vinyl propionate) and commercial lipases from Candida rugosa and Candida antarctica (Novozym® 435) were studied. Phenolic terpenes were not detected to have participated in the transesterification reaction and were therefore not modified, which could be attributed to the position of the hydroxyl group on their phenyl moiety. Geraniol was successfully modified in toluene and a solvent-free medium utilizing lemon oil as the reaction medium, with bioconversion yields as high as 100% and 88%, respectively. These findings revealed the efficiency of solvent-free modification of terpene alcohols in essential oils. This method could, therefore, be considered to modify essential oils to be used as functional ingredients in food products. • Lipase from Candida rugosa and Novozym® 435 can modify geraniol with vinyl esters. • Novozym® 435 exhibited the highest acylation yields (41–100%). • Geraniol can undergo solvent-free transesterification by Novozym® 435 in lemon oil. • The solvent-free reaction reached 89% acylation yield in 15 h with vinyl esters. • Enzymatic modification of essential oils can broaden their applications.

A Fischer-Type Ruthenium Carbene Complex as a Metathesis Catalyst for the Synthesis of Enol Ethers.

The Grubbs G-I or G-II catalyst gives the ruthenium ethoxy carbene complex, which catalyzes ring-opening cross metathesis (ROCM) of a strained cyclic alkene to give a diene where one of the two alkene moieties in the product contains an ethoxy substituent. No polymeric products are detected. Hydrocarbons such as parent norbornene or substituted cyclopropenes can proceed with the reaction smoothly. Tertiary amines, N-alkylimides, esters, and aryl or alkyl bromides remain intact under the reaction conditions. In addition to vinyl ethers, vinylic esters can also be used. The time required to reach a 50% yield of the ROCM product t50 varies from 0.01 to 140 h depending on the strain and nucleophilicity of the double bond. Anchimeric participation of an electron-rich group would result in significant enhancement of the reactivity, and the t50 could be as short as several minutes. A similar substrate without such a neighboring group shows a much slower rate. An exo-norborne derivative reacts much faster than the corresponding endo-isomer. Alkenes with poor nucleophilicity are less favored for the ROCM process, so is less strained cyclooctene.

Selective Palladium‐Catalyzed α,β‐Homodiarylation of Vinyl Esters in Aqueous Medium

AbstractA palladium‐catalyzed 1,2‐diarylation of vinyl esters with arylboronic acids in water has been developed. This newly elaborated protocol features a good functional group tolerance and provides one‐step access to 1,2‐diarylethanol derivatives under mild reaction conditions. The presented reaction can be carried out in the water at ambient temperature without the addition of any ligands, what makes this procedure environmentally benign. The transformation occurs within a single catalytic cycle and is feasible due to the modification of transition metal catalytic activity through the influence of π‐acceptor olefin (benzoquinone) as well as water as a medium. Moreover, this protocol allows to generate entire compound libraries (highly profitable in medicinal chemistry) and utilizes sustainable arylboronic acids as coupling partners under mild conditions. It is also noted that the structure of boron moiety has a great impact on the reaction selectivity, the usage of sterically hindered esters of arylboronic acids influence the reaction course towards stilbenes.

Enzymatic acylation of lutein with a series of saturated fatty acid vinyl esters and the thermal stability and anti-lipid oxidation properties of the acylated derivatives.

Lutein was enzymatically acylated with saturated fatty acid vinyl esters of different lengths of carbon chain (C6 -C14 ) under the action of Candida antarctica lipase B (Novozyme 435). The acylation reaction was optimized by considering substrate molar ratio, reaction solvent, type of enzyme, and reaction time. The highest yield (88%) was obtained using the Novozyme 435 to catalyze the acylation reaction of lutein and vinyl decanoate (lutein/vinyl decanoate molar ratio of 1/10) for 16 h in methyl tert-butyl ether. Ten lutein esters were synthesized, isolated, and purified, which were characterized by Fourier-transform infrared spectroscopy, high-resolution mass spectrometry, and nuclear magnetic resonance spectroscopy. We found that the acylation of lutein improved its antioxidant capacity in lipid system and thermal stability. Our study extended the potential application of lutein in lipophilic food, cosmetic, and pharmaceutical industries. Practical Application: Enzyme acylation of lutein improved its antioxidant capacity in lipid system and thermal stability, extended its potential application in food, cosmetic, and pharmaceutical industries. In addition, our study also provided a new perspective and cognition for the further development and utilization of lutein.

Approaching new biomaterials: copolymerization characteristics of vinyl esters with norbornenes, allyl esters and allyl ethers

AbstractVinyl ester‐based monomers for radical photopolymerization have recently been shown to be promising alternatives to (meth)acrylates through lower irritancy and cytotoxicity. Vinyl ester monomers are becoming increasingly important on account of new, more cost‐efficient synthetic production methods, not to forget their increased reactivity and improved material properties in combination with thiol–ene polymerization. Due to their biocompatibility and degradability, these monomers are more frequently used in tissue engineering. Nevertheless, the material properties can be improved by possible copolymerizations with other monomers. Therefore, the copolymerization behavior of vinyl ester with norbornene, allyl ether and allyl ester has been studied fundamentally in a photoreactor via free radical photopolymerization. Here, the consumption of double bonds of the monomers has been identified using NMR spectroscopy. Copolymerization parameters have been determined using the Kelen–Tüdös method. Results show equal consumption of vinyl ester and co‐monomer double bonds leading to alternating copolymerizations. The double bond conversion was confirmed via in situ real‐time near‐infrared photorheology. Mono‐ and difunctional vinyl esters with co‐monomers have also provided further insight into the polymer network of these copolymers. © 2021 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.

Mechanochemical Synthesis of Primary Amides.

Ball milling of aromatic, heteroaromatic, vinylic, and aliphatic esters with ethanol and calcium nitride afforded the corresponding primary amides in a transformation that was compatible with a variety of functional groups and maintained the integrity of a stereocenter α to carbonyl. This methodology was applied to α-amino esters and N-BOC dipeptide esters and also to the synthesis of rufinamide, an antiepileptic drug.

Some peculiarities of the kinetics of interaction of cationic hydrogels based on copolymers of vinyl esters of monoethanolamine and ethylene glycol with copper ions

Over the past few decades, formation of polymer hydrogels complexes with metal ions, including transition ones, attracts the steady attention of researchers. The relevance of such study is due to the fact that the kinetics of swelling and contraction of hydrogels in various media has been studied in many works, however, this question remains insufficiently studied. Cationic hydrogels based on copolymer of vinyl ethers of monoethanolamine (VEMEA) and ethylene glycol (VEEG) as the study subject in the present work have been used. The kinetics of interaction cationic hydrogels based on copolymer of vinyl ethers of monoethanolamine and ethylene glycol with copper ions in aqueous solutions has been studied. It was shown that swelling behavior such hydrogel in this process is characterized two stages. At the initial stages of the interaction of the gel with the copper salt solution, the interaction in question is determined mainly by the displacement of water from the swollen mesh, due to the difference in osmotic pressures inside and outside the sample. At this stage, the kinetics of the gel contraction is described by the same laws as for polyelectrolyte hydrogel in the alkali metal solution. At the second stage, the network charge density increases due to the formation of a complex, and the degree of the gel swelling begins to increase with time. On the basis of the results obtained, it can be assumed that in systems of this kind, metastable states with differences in character from truly equilibrium states, persisting for a long time, can be formed.