Unsaturated Carboxylic Acids Research Articles

Alkaloids of Lindelofia macrostyla and a New Unsaturated Carboxylic Acid

Alkaloids of Lindelofia macrostyla and a New Unsaturated Carboxylic Acid

Decarboxylation of Aza-Annulation Products as a Synthetic Route to 3-Pyrrolin-2-ones and 1,2,3,4-Tetrahydropyridin-2-ones.

Aza-annulation of enamines derived from β-ketoesters with maleic and itaconic anhydrides proceeds with excellent diastereoselectivity to provide functionalized γ- and δ-lactams. Further hydrolysis of the aza-annulation products resulted in dicarboxylic acids that underwent spontaneous decarboxylation under ambient conditions. The decarboxylation of β-γ unsaturated carboxylic acids with an electron-rich enamide C═C bond proceeds with the migration of the C═C bond and serves as a practical synthetic entry into 3-pyrrolin-2-ones and 1,2,3,4-tetrahydropyridin-2-ones.

Construction of MIL-100(Fe)-DMA material for efficient adsorption of Sr and Cs ions from radioactive wastewater

A novel metal-organic framework (MOF) material, MIL-100(Fe)-DMA, was synthesized using the solvothermal method. The structure of the MOF was characterized using scanning electron microscopy-energy dispersive X-ray spectroscopy, N2 adsorption–desorption isotherms, X-ray diffraction analysis, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and Mössbauer spectroscopy. Batch adsorption experiments were performed to investigate the effects of initial Sr2+ and Cs+ concentrations, adsorption time, pH, and coexisting cations on the adsorption performance of the material. The adsorption mechanism was further elucidated using adsorption kinetics and isotherm models. The results indicated that the adsorption of Sr2+ and Cs+ does not significantly affect the MOF material structure. As reaction time and initial ion concentration increased, the adsorption capacity of MIL-100(Fe)-DMA for Sr2+ and Cs+ increased rapidly and then gradually reached equilibrium. Optimal adsorption occurred under alkaline conditions, with maximum adsorption capacity observed at pH = 8. The adsorption process for Sr2+ and Cs+ was well described by the pseudo-second-order kinetic model, the Weber–Morris model, and the Langmuir adsorption isothermal model. The adsorption process was mainly identified as monolayer chemical adsorption, influenced by multiple factors. Characterization combined with density functional theory calculations revealed that the unsaturated carboxylic acid groups on the surface of the MOFs play a crucial role in the interaction with Sr2+ and Cs+.

(Invited) Design of Reduced Shear Force Cu Cleaning Processes Via α-β-Unsaturated Chemistries for Enhanced BTA Residue Removal

As integrated circuit and logic devices continue to decrease, limiting induced defectivity during Chemical Mechanical Planarization (CMP) processes (polishing and substrate cleaning) is imperative. Defects resulting from the CMP process can be classified as mechanical (i.e., scratching), chemical (i.e., corrosion), or physiochemical (i.e., adsorbed contaminants) according to the mechanism of formation. Traditionally, a contact cleaning method implements a polyvinyl alcohol (PVA) brush to transfer cleaning chemistry to the substrate of interest and provides the necessary mechanical energy for defect removal. While this process effectively removes contaminants, its reliance on shear forces can induce secondary defect modes, such as scratching. One major challenge for the post-CMP cleaning of Cu substrates is the polymeric residue film comprised of BTA-Cu+ complexes that propagate during the CMP polishing process. The current and most effective mode to mitigate this “residue defect” is coupling brush-induced shear force with additives that promote interfacial redox reactions to remove residues through an undercutting mechanism. This work focuses on developing a “softer” and additive structure-based approach that drives less aggressive interfacial shear between the brush and wafer substrate. More specifically, α-β-unsaturated additives with diverse functionality (i.e., -unsaturated carboxylic acids, carboxylic acids, and unsaturated benzaldehydes) will be tested to evaluate their efficacy to “overcut” the organic residue via a proposed aza-Michael addition reaction pathway. This “overcutting” mechanism relies on additional modes of interaction (i.e., p-stacking, H-bonding, conformational relationships, etc.) with the BTA- Cu+ polymeric residue film. A suite of dynamic techniques (i.e., Tafel analysis, OCP vs. time, contact angle, additive diffusion analysis, and shear force) will attempt to correlate the additive structure and reaction mechanism to organic residue removal efficiency and measured interfacial shear forces. Initial results have shown that implementing an “overcutting” mechanism will decrease the overall shear force and significantly reduce the generation of secondary defects without sacrificing overall defect removal efficiency.

Electron bifurcation and fluoride efflux systems implicated in defluorination of perfluorinated unsaturated carboxylic acids by Acetobacterium spp.

Enzymatic cleavage of C─F bonds in per- and polyfluoroalkyl substances (PFAS) is largely unknown but avidly sought to promote systems biology for PFAS bioremediation. Here, we report the reductive defluorination of α, β-unsaturated per- and polyfluorocarboxylic acids by Acetobacterium spp. The microbial defluorination products were structurally confirmed and showed regiospecificity and stereospecificity, consistent with their formation by enzymatic reactions. A comparison of defluorination activities among several Acetobacterium species indicated that a functional fluoride exporter was required for the detoxification of the released fluoride. Results from both in vivo inhibition tests and in silico enzyme modeling suggested the involvement of enzymes of the flavin-based electron-bifurcating caffeate reduction pathway [caffeoyl-CoA reductase (CarABCDE)] in the reductive defluorination. This is a report on specific microorganisms carrying out enzymatic reductive defluorination of PFAS, which could be linked to electron-bifurcating reductases that are environmentally widespread.

INFLUENCE OF EXTERNAL FACTORS ON BINARY SYSTEMS DURING RAFT POLYMERIZATION

The article discusses the method of radical copolymerization as an effective way to obtain new polymer compounds with practically valuable properties. This method is based on the free radical mechanism, in which the sequential addition of molecules of an unsaturated monomeric compound to a growing macroradical occurs. Due to the relative simplicity of this method, it makes it possible to produce a large number of polymers for various purposes on an industrial scale. Unsaturated polyesters of various compositions and molecular weights, which can significantly affect the properties of the final products, are considered promising coreagents capable of entering into radical copolymerization reactions with vinyl monomers. The article discusses the results of studies of polymer gels obtained on the basis of unsaturated carboxylic acids. The author refers to previous studies, showing that such gels have high sorption capacity, while the starting material does not have similar properties. The following describes the structure analysis of p-PGFPh copolymers with these acids, where important characteristics such as the presence of ionized units in vinyl monomers are discussed. The significance of these studies for the creation of materials with the necessary properties of sorption and interaction with other substances. Study of the influence of environmental pH on the behavior of copolymers based on polypropylene glycol fumarate phthalate with acrylic and methacrylic acids. The equilibrium degree of swelling of the studied copolymers in aqueous solutions at different temperatures was also determined by the gravimetric method. In general, analysis of the swelling curve when varying the acidity/alkalinity of the external solution indicates that the gels we synthesized are polyelectrolytes; analysis of the curve when exposed to temperature, the resulting copolymers are thermosensitive. Thus, the main idea of the article is the importance of using unsaturated carboxylic acids to create polymer gels with high sorption capacity and emphasizes the importance of analyzing the structure of such materials to understand their properties and application possibilities.

Methacrylic acid in situ modified steel converter slag/natural rubber composites: Resourceful utilization of steelmaking solid wastes

As a by-product of the steelmaking industry, the large-volume production and accumulation of steel converter slag cause environmental issues such as land occupation and dust pollution. Since metal salts of unsaturated carboxylic acid can be used to reinforce rubber, this study explores the innovative application of in-situ modified steel slag, mainly comprising metal oxides, with methacrylic acid (MAA) as a rubber filler partially replacing carbon black. By etching the surface of steel slag particles with MAA, their surface roughness was increased, and the chemical bonding of metal methacrylate salt was introduced to enhance their interaction with the molecular chain of natural rubber (NR). The results showed that using the steel slag filler effectively shortened the vulcanization molding cycle of NR composites. The MAA in-situ modification effectively improved the interaction between steel slag and NR molecular chains. Meanwhile, the physical and mechanical properties, fatigue properties, and dynamic mechanical properties of the experimental group with MAA in-situ modified steel slag (MAA-in-situ-m-SS) were significantly enhanced compared with those of NR composites partially filled with unmodified slag. With the dosage of 7.5 phr or 10 phr, the above properties matched or even exceeded those of NR composites purely filled with carbon black. More importantly, partially replacing carbon black with modified steel slag reduced fossil fuel consumption and greenhouse gas emission from carbon black production. This study pioneered an effective path for the resourceful utilization of steel slag and the green development of the steelmaking and rubber industries.

Distinctive biotransformation and biodefluorination of 6:2 versus 5:3 fluorotelomer carboxylic acids by municipal activated sludge

Fluorotelomer carboxylic acids (FTCAs) represent an important group of per- and polyfluoroalkyl substances (PFAS) given their high toxicity, bioaccumulation potential, and frequent detection in landfill leachates and PFAS-impacted sites. In this study, we assessed the biodegradability of 6:2 FTCA and 5:3 FTCA by activated sludges from four municipal wastewater treatment plants (WWTPs) in the New York Metropolitan area. Coupling with 6:2 FTCA removal, significant fluoride release (0.56∼1.83 F-/molecule) was evident in sludge treatments during 7 days of incubation. Less-fluorinated transformation products (TPs) were formed, including 6:2 fluorotelomer unsaturated carboxylic acid (6:2 FTUCA), perfluorohexanoic acid (PFHxA), perfluoropentanoic acid (PFPeA), and perfluorobutanoic acid (PFBA). In contrast, little fluoride (0.01∼0.09 F-/molecule) was detected in 5:3 FTCA-dosed microcosms, though 25∼68% of initially dosed 5:3 FTCA was biologically removed. This implies the dominance of “non-fluoride-releasing pathways” that may contribute to the formation of CoA adducts or other conjugates over 5:3 FTCA biotransformation. The discovery of defluorinated 5:3 FTUCA revealed the possibility of microbial attacks of the C-F bond at the γ carbon to initiate the transformation. Microbial community analysis revealed the possible involvement of 9 genera, such as Hyphomicrobium and Dechloromonas, in aerobic FTCA biotransformation. This study unraveled that biotransformation pathways of 6:2 and 5:3 FTCAs can be divergent, resulting in biodefluorination at distinctive degrees. Further research is underscored to uncover the nontarget TPs and investigate the involved biotransformation and biodefluorination mechanisms and molecular basis.

Preparation and performance study of anti mud polycarboxylic acid slump retaining agent

Anti-mud polycarboxylic acid slump retaining agent was prepared by copolymerization of ethylene glycol monovinyl polyethylene glycol ether, diethyl 4-vinylphenyl phosphate, 2-methyl-2-(4-vinylphenyl) propionic acid, unsaturated carboxylic acid (or unsaturated carboxylic anhydride) and unsaturated carboxylic ester under the action of initiator and molecular weight regulator. The effect of the slump retaining agent on the workability of fine aggregate concrete with different mud contents was tested, and the sensitivity of the slump retaining agent to the mud content of machine-made sand was evaluated. At the same time, the viscosity reduction performance of the slump retaining agent was evaluated by using the emptying time of the inverted slump cone and the flow time of V-funnel and L-box. The experimental results show that the synthesized anti-mud polycarboxylic acid slump retaining agent has favourable effects of anti-mud and viscosity reduction.

(De)carboxylation mechanisms of heteroaromatic substrates catalyzed by prenylated FMN-dependent UbiD decarboxylases: An in-silico study

The UbiD enzymes are proposed to catalyze reversible (de)carboxylation reaction of unsaturated carboxylic acids using prenylated flavin mononucleotide (prFMN) as a cofactor. This positions UbiD enzymes as promising candidates for converting CO2 into valuable chemicals. However, their industrial-scale biotransformation is currently constrained by low conversion rates attributed to thermodynamic limitations. To enhance the carboxylation activity of UbiD enzymes, a molecular-level understanding of the (de)carboxylation mechanisms is necessary. In this study, we investigated the reaction mechanisms of heteroaromatic substrates catalyzed by PtHmfF, PaHudA, and AnlnD enzymes using molecular dynamics (MD) simulations and free energy calculations. Our extensive mechanistic study elucidates the mechanisms involved in the formation of the initial prFMN-substrate intermediate. Specifically, we observed nucleophilic attack during decarboxylation, while carboxylation reactions involving furoic acid, pyrrole, and indole tend to favor a 1,3-dipolar cycloaddition mechanism. Furthermore, we identified proton transfer as the rate-limiting step in the carboxylation reaction. In addition, we considered the perspectives of reaction energies and electron transfer to understand the distinct mechanisms underlying decarboxylation and carboxylation. Our calculated free energies are consistent with available experimental kinetics data. Finally, we explored how different rotamers of catalytic residues influence the efficiency of the initial intermediate formation.

Controlling the regioselectivity of the bromolactonization reaction in HFIP.

The halolactonization reaction provides rapid access to densely functionalized lactones from unsaturated carboxylic acids. The endo/exo regioselectivity of this cyclization reaction is primarily determined by the electronic stabilization of alkene substituents, thus making it inherently dependent on substrate structures. Therefore this method often affords one type of halolactone regioisomer only. Herein, we introduce a simple and efficient method for regioselectivity-switchable bromolactonization reactions mediated by HFIP solvent. Two sets of reaction conditions were developed, each forming endo-products or exo-products in excellent regioselectivity. A combination of computational and experimental mechanistic studies not only confirmed the crucial role of HFIP, but also revealed the formation of endo-products under kinetic control and exo-products under thermodynamic control. This study paves the way for future work on the use of perfluorinated solvents to dictate reaction outcomes in organic synthesis.

PdPt/SrTiO3:Al-catalysed redox-selective photoreduction of unsaturated carboxylic acids using minimal electron-donor and water.

We developed a semiconductor photocatalyst, Pd-Pt alloy nanoparticle-loaded, Al-doped SrTiO3 (PdPt/STO:Al), for photoreduction of unsaturated carboxylic acids. Due to the cooperative STO:Al surface and Pd-Pt alloy nanoparticles, the catalyst dispersed in water provided highly redox-selective photoreduction against oxidative degradation of starting materials/products and against reductive evolution of H2, where minimal glycolic acid worked as an efficient electron-donating fuel.

Surveying the scope of aromatic decarboxylations catalyzed by prenylated-flavin dependent enzymes.

The prenylated-flavin mononucleotide-dependent decarboxylases (also known as UbiD-like enzymes) are the most recently discovered family of decarboxylases. The modified flavin facilitates the decarboxylation of unsaturated carboxylic acids through a novel mechanism involving 1,3-dipolar cyclo-addition chemistry. UbiD-like enzymes have attracted considerable interest for biocatalysis applications due to their ability to catalyse (de)carboxylation reactions on a broad range of aromatic substrates at otherwise unreactive carbon centres. There are now ∼35 000 protein sequences annotated as hypothetical UbiD-like enzymes. Sequence similarity network analyses of the UbiD protein family suggests that there are likely dozens of distinct decarboxylase enzymes represented within this family. Furthermore, many of the enzymes so far characterized can decarboxylate a broad range of substrates. Here we describe a strategy to identify potential substrates of UbiD-like enzymes based on detecting enzyme-catalysed solvent deuterium exchange into potential substrates. Using ferulic acid decarboxylase (FDC) as a model system, we tested a diverse range of aromatic and heterocyclic molecules for their ability to undergo enzyme-catalysed H/D exchange in deuterated buffer. We found that FDC catalyses H/D exchange, albeit at generally very low levels, into a wide range of small, aromatic molecules that have little resemblance to its physiological substrate. In contrast, the sub-set of aromatic carboxylic acids that are substrates for FDC-catalysed decarboxylation is much smaller. We discuss the implications of these findings for screening uncharacterized UbiD-like enzymes for novel (de)carboxylase activity.

Effect of Structure to Promote Organic Residue Removal during Cu Post-Chemical Mechanical Planarization (p-CMP) Cleaning

The extension of Moore’s law remains a focal point as semiconductor manufacturers drive to advance Integrated Circuit (IC) technology by implementing new materials. Chemical Mechanical Planarization (CMP) has emerged as a critical processing step in device fabrication to keep up with these demands. However, one drawback to this process is the generation of killer defects that result from residual contamination (i.e., organic residues, abrasive particles, pad remnants, etc.) that are reliant on post-CMP (p-CMP) cleaning methods. Current Cu p-CMP cleaning methods implement the use of an industry standard polymer brush coupled with cleaning chemistries to remove residual contamination. It has been well established that shear and compressive forces coupled with surface active cleaning chemistries have proven to be efficient albeit with the potential for secondary defectivity (i.e., pitting, etching, scratching). Additionally, current cleaning formulations rely on additives that promote aggressive redox conditions to remove residues through an undercutting mechanism, which leads to the propagation of the aforementioned defect modes. This work focuses on the development of a “softer” approach to Cu p-CMP cleaning by surveying various additives (i.e., -unsaturated carboxylic acids, carboxylic acids, and unsaturated benzaldehydes) to exploit an “overcutting” mode of organic residue removal. By implementing additional modes of interaction (i.e., p-stacking, H-bonding, conformational relationships, etc.), the mode of residue removal can be finely tuned to achieve desired surface-active conditions. This work employs a suite of techniques (i.e., Tafel analysis, OCP vs. time, time-resolved contact angle, shear force analysis) to correlate structure-activity to organic residue removal efficiency and the effects on the coefficient of friction (COF), particle removal efficiency, and the generation of secondary defectivity. Initial results have shown that implementing an “overcutting” mechanism will decrease the overall shear force and significantly reduce the proliferation of p-CMP cleaning defects. Furthermore, adding ancillary structure activity aids in additional modes of residue interaction to alter removal at the liquid-brush interface. Additionally, increased structure-activity has promoted residue-chemistry interactions to form a second passivation layer. Moreover, conformational changes that result in limited accessibility to the a,b-unsaturated double bond promote an “undercutting” mode of removal to become the predominant mode of organic residue mediation.

FSO2 Radical-Initiated Photoredox Cyclization of 4-Enoic Acids to Functionalized γ-Lactones

AbstractThe incorporation of sulfonyl fluoride groups into molecules has been proven effective in enhancing their biological activities or introducing new functions. Herein, a transition-metal-free and visible-light-mediated radical tandem cyclization of unsaturated carboxylic acid is reported. This affords a facile access to FSO2-functionalized γ-lactones efficiently, which are critical structural motifs widely present in biologically active molecules.

Olefination of Aromatic Carbonyls via Site‐Specific Activation of Cycloalkanone Ketals**

AbstractSkeletal editing is an important strategy in organic synthesis as it modifies the carbon backbone to tailor molecular structures with precision, enabling access to compounds with specific desired properties. Skeletal editing empowers chemists to transform synthetic approaches of target compounds across diverse applications from drug discovery to materials science. Herein, we introduce a new skeletal editing method to convert readily available aromatic carbonyl compounds into valuable unsaturated carboxylic acids with extended carbon chains. Our reaction setup enables a cascade reaction of enolization‐[2+2]cycloaddition‐[2+2]cycloreversion between aromatic carbonyl compounds and ketals of cyclic ketones to generate unsaturated carboxylic acids as ring‐opening products. Through a simple design, our substrates are specifically activated to react at predetermined positions to enhance selectivity and efficiency. This practical method offers convenient access to versatile organic building blocks as well as provides fresh insights into manipulating traditional reaction pathways for new synthetic applications.

Development of polymer-immobilised acridinium catalyst and its application in photoinduced 1,4-addition to α,β-unsaturated carbonyl compounds

Efficient heterogeneous catalysts for green and sustainable chemistry are in high demand. In this study, a novel polymer-immobilised acridinium salt was developed, and it was found to catalyse the visible-light-induced 1,4-addition of phenylmalononitrile to α,β -unsaturated carboxylic acids. The catalyst was easy to recover after the reaction and was sufficiently robust to maintain its catalytic activity for several uses without a significant decrease in product yield.

Catalytic Carbonylation of Acrylic Acid to Succinic Anhydride**

AbstractAlternative sources for polymeric materials have been sought in the past few years to reduce our dependence on fossil feedstock. We report the catalytic carbonylation of acrylic acid, a platform chemical that can be bio‐sourced, as a new pathway toward the formation of a useful monomer to polyesters, namely succinic anhydride. The novel system reported herein tackles the difficult carbonylation of unsaturated carboxylic acids through the utilization of an Earth‐abundant metal catalyst, [Co2(CO)8], in presence of a bidentate ligand, 1,2‐bis(dicyclohexylphosphino)ethane (dcpe), and H2. We investigated the influence of the reaction conditions through the variations of metal, ligand, temperature, pressure, and gas composition. The carbonylative ring‐closure of acrylic acid was successfully obtained in high yield and selectivity toward the formation of succinic anhydride using mild conditions (90 °C and 16 bar of CO/H2 95 : 5).

Effect of crystal structure on photoreactivity of unsaturated carboxylic acids in the solid state

Effect of crystal structure on photoreactivity of unsaturated carboxylic acids in the solid state

Degradation and Defluorination of Per- and Polyfluoroalkyl Substances by Direct Photolysis at 222 nm.

The susceptibility of 19 representative per- and polyfluoroalkyl substances (PFAS) to direct photolysis and defluorination under far-UVC 222 nm irradiation was investigated. Enhanced photolysis occurred for perfluorocarboxylic acids (PFCAs), fluorotelomer unsaturated carboxylic acids (FTUCAs), and GenX, compared to that at conventional 254 nm irradiation on a similar fluence basis, while other PFAS showed minimal decay. For degradable PFAS, up to 81% of parent compound decay (photolysis rate constant (k222nm) = 8.19-34.76 L·Einstein-1; quantum yield (Φ222nm) = 0.031-0.158) and up to 31% of defluorination were achieved within 4 h, and the major transformation products were shorter-chain PFCAs. Solution pH, dissolved oxygen, carbonate, phosphate, chloride, and humic acids had mild impacts, while nitrate significantly affected PFAS photolysis/defluorination at 222 nm. Decarboxylation is a crucial step of photolytic decay. The slower degradation of short-chain PFCAs than long-chain ones is related to molar absorptivity and may also be influenced by chain-length dependent structural factors, such as differences in pKa, conformation, and perfluoroalkyl radical stability. Meanwhile, theoretical calculations indicated that the widely proposed HF elimination from the alcohol intermediate (CnF2n+1OH) of PFCA is an unlikely degradation pathway due to high activation barriers. These new findings are useful for further development of far-UVC technology for PFAS in water treatment.