Decarboxylation Research Articles

Acid-catalyzed transformation of orange waste into furfural: the effect of pectin degree of esterification

The transformation of biomasses from agro-industrial waste can significantly impact the production of green chemicals from sustainable resources. Pectin is a biopolymer present in lignocellulosic biomass as Orange Peel Waste (OPW) and has possibilities for making platform compounds such as furfural for sustainable chemistry. In this work, we studied the transformation to furfural of OPW, pectins, and d-galacturonic acid (D-GalA), which is the main component (65 wt%) of pectin. We analyzed pectins with different degrees of esterification (45, 60 and 95 DE) in a one-pot hydrolysis reaction system and studied the differences in depolymerization and dehydration of the carbohydrates. The results show that the production of furfural decreases as the DE value increases. Specifically, low DE values favor the formation of furfural since the decarboxylation reaction is favored over deesterification. Interestingly, the furfural concentration is dependent upon the polysaccharide composition of pentoses and uronic acid. The obtained concentrations of furfural (13 and 14 mmol/L), d-xylose (6.2 and 10 mmol/L), and L-arabinose (2.5 and 2.7 mmol/L) remained the same when the galacturonic acid was fed either as a polymer or a monomer under the same reaction conditions (0.01 M SA, 90 min and 433 K). OPW is proposed as a feedstock in a biorefinery, in which on a per kg OPW dry basis, 90 g of pectin and 15 g of furfural were produced in the most favorable case. We conclude that the co-production of pectin and furfural from OPW is economically feasible.Graphical

Investigation of Metabolic Responses in Virus-infected Wheat (Triticum aestivum L.) Grown in Azerbaijan

Barley yellow dwarf viruses (BYDV), Wheat streak mosaic virus (WSMV), Wheat dwarf virus (WDV), and Soil-borne wheat mosaic virus (SBWMV) constitute the most dangerous and widespread viruses affecting cereals across all wheat-growing regions worldwide. While numerous foreign scientific reports focus on the impact of climate change on plants, pathogens, and their vectors, only a limited number of studies address cereal viruses. The objective of this study was to investigate the variability of economically significant wheat viruses in several regions of Azerbaijan and to identify certain metabolic enzymes such as malate dehydrogenase (MDH), aspartate aminotransferase (AsAT), and alanine aminotransferase (ALAT) in virus-infected wheat samples. During 2022-2023, it was observed that BYDV and WSMV alternated in prevalence from year to year, with no instances of co-infection recorded. SBWMV was not detected in the tested samples. WSMV incidence rates were 12.4% and 19% in 2022 and 2023, respectively, whereas BYDV was detected at rates of 14.6% and 8.5%, respectively. Our results support a tight relationship between amino acid metabolism and stress responses. The results of the research allow the conclusion that mitochondrial NAD-MDH implements oxidation of NADH reduced in the reaction of glycine decarboxylation during photorespiration and intensifies biosynthesis of 2-oxoglutarate playing the role of the carbon skeleton in the synthesis of amino acids.

Rapid screening of tuna samples for food safety issues related to histamine content using fourier-transform mid-infrared (FT-MIR) and chemometrics

Biogenic amines (BAs) generally result from the decarboxylation reaction of free amino acids as a result of the activity of different microorganisms. A build-up of these compounds can result in food being spoilt. Therefore, the rapid and precise detection of BAs like histamine is an important task for food safety. This research aimed to explore the potential of Fourier-Transform Mid-Infrared (FT-MIR) spectroscopy combined with chemometric methods to assess histamine in fresh tuna quantitatively. Based on the FT-MIR data, partial least squares regression models for the prediction of histamine were successfully constructed with R2 > 0.90. Machine learning algorithms (partial least squares-discrimination analysis, k-nearest neighbors, and support vector machine) were applied, and excellent discrimination results were achieved based on the limits specified in two different legislations (EU and FDA). The results support the use of a rapid, economic and reliable approach for the discrimination of samples that could pose a health risk to consumers.

Enhanced catalytic activity of Sm/CeO2 to produce gasoline-range hydrocarbons from pyrolysis of spent coffee grounds

This study investigated the application of Sm/CeO2 catalyst for hydrocarbon production in catalytic pyrolysis (CP) of spent coffee grounds (SCGs). A temperature range of 450–750 °C and catalyst/biomass (C/B) ratios of 0.5–4 were employed in the CP. The results showed that an increase in pyrolysis temperature consistently increased the quantity of hydrocarbons and considerably decreased the oxygenated compounds like acids and phenols. At temperatures of 450 and 550 °C, C/B ratios of 2 or 1 generated the maximum amount of hydrocarbons. At 650 and 750 °C temperatures, C/B ratios of 0.5 and 1 were capable to achieve a higher content of hydrocarbons in bio-oils, suggesting the synergistic effect of temperature and catalyst activity. The hydrocarbons in bio-oils were found in the gasoline range, mainly containing benzene, toluene, ethylbenzene, xylene (BTEX), olefins, and cycloalkenes. Primary reactions involved to convert oxygenated compounds into hydrocarbons were dehydration, decarboxylation, decarbonylation, dehydrogenation, isomerization, and aromatization reactions.

Self-blowing, hybrid non-isocyanate polyurethane foams produced at room temperature

Self-blowing polyurethane foams are essential for several everyday applications, yet their traditional production involves fossil-derived products and hazardous isocyanate compounds. Thus, research into isocyanate-free polyurethane foams is receiving considerable attention. However, current approaches often rely on external blowing agents, and/or high temperatures with long polymerization times. This research presents a rapid, self-blowing, partially bio-based non-isocyanate polyurethane (NIPU) foams at room temperature, specifically poly(hydroxy-thio-urethane), with both rigid and flexible configurations. The method involves the partial conversion of an epoxy resin to an oligomer mixture composed of 85% bio-cyclic carbonate and 15% of non-converted epoxide. This oligomer undergoes a fast process, through reactions between the epoxy groups and the reactive components, that is then followed by simultaneous aminolysis and decarboxylation reactions, arising from the interaction of an amine and cyclic carbonate. An in-situ blowing agent (CO2) is generated from the interaction between thiols and cyclic carbonate. The glass transition temperature is modulated by the thiol/amine content in rigid foams and by the addition of aliphatic long chains in flexible foams. With almost 30% renewable carbon content, these foams provide a sustainable alternative to traditional isocyanate-based pathways. The resulting porous materials possessed densities between 0.158 and 0.201 g/cm3. Finally, the foams can be transformed into films, enhancing recyclability and sustainability at the end of their lifecycle. Thus, this development has the potential to facilitate the production of eco-friendly, recyclable polyurethane foams.

Photoredox-Catalyzed Decarboxylative Cross-Coupling Reaction to Synthesis Unsymmetrical Diarylmethanes.

The photoredox-catalyzed decarboxylative cross-coupling reaction of aryl acetic acids and aryl nitriles has been achieved under an argon atmosphere in high yields. This method provides a fast way to obtain prevalent aryl acetic acids from an abundant natural source. A tentative radical mechanism has been proposed.

Flavor formation by amino acid catabolism in low-salt sufu paste, a Chinese fermented soybean food

In this study, the low-salt sufu paste was fermented enhanced by a mixed starter (Pichia fermentans, Kodamaea ohmeri and Lactococcus lactis subsp.) and α-ketoglutarate. Multispecies microbial community is crucial for the flavor formation of sufu paste during post-ripening. Consequently, the primary biochemical pathways of the flavor formation were analyzed using a metagenomic approach in conjunction with gas chromatography mass spectrometry (GC-MS). After post-ripening for 15 d, a total of 86 volatile flavor compounds (VFCs) were tentatively identified, in which 6 compounds were recognized as the main characteristic VFCs. The metagenomics revealed that Actinomucor elegans, Lactobacillus fermentum, Lactococcus lactis subsp., Pichia fermentans, Lactobacillus delbrueckii and Propionibacterium acidipropionici were the dominant species. According to the functional annotation, amino acid metabolisms were identified as the predominant pathways for flavor formation. Among them, aromatic amino acids metabolisms accounted for the highest proportion, up to 41.3%. The VFCs formation pathways mainly involved transamination, decarboxylation, dehydrogenation and oxidation reaction. The amino acid transamination was proposed as a crucial step in VFCs formation, and the corresponding aminotransferases were the key rate-limiting enzymes. These findings have implications for enhancing the flavor quality of sufu paste and elucidating the mechanism of flavor formation in traditional soybean fermented food.

Effect of traditional solvent on thermal decomposition mechanism of lignin: A density functional theory study

In order to understand the effect of traditional solvents on lignin pyrolysis, the decarbonylation and decarboxylation reactions of various phenylic lignin model compounds were theoretically investigated using DFT methods at M06-2×/6–31++G(d,p) level. The calculation results show that activation energy of the decarbonylation and decarboxylation reactions of lignin model compounds can be reduced when H2O/CH3OH existed. There are two types of reaction for the H2O/CH3OH during the pyrolysis. For first type, the synergistic reaction of lignin with H2O/CH3OH as hydrogen transfer carrier. The energy barriers of the main elemental reaction steps during this type of pyrolysis are about 285.0–300.0 kJ/mol (H2O) and 275.0–290.0 kJ/mol (CH3OH) (decarbonylation), 170.0–210.0 kJ/mol and 155.0–200.0 kJ/mol (decarboxylation). For another type, the synergistic reaction of lignin with H2O/CH3OH as hydrogen source. The energy barriers of the main elemental reaction steps during this type of pyrolysis are about 260.0–278.0 kJ/mol and 240.0–260.0 kJ/mol, 303.0–312.0 kJ/mol and 291.0–297.0 kJ/mol. Furthermore, the reaction temperature has the most significant impact on decomposition reaction of lignin in a methanol medium, suggesting that the reaction in the methanol medium is better than that in the water environment.

Hydrothermal Destruction and Defluorination of Trifluoroacetic Acid (TFA).

Per- and polyfluoroalkyl substances (PFAS) have received increased attention due to their environmental prevalence and threat to public health. Trifluoroacetic acid (TFA) is an ultrashort-chain PFAS and the simplest perfluorocarboxylic acid (PFCA). While the US EPA does not currently regulate TFA, its chemical similarity to other PFCAs and its simple molecular structure make it a suitable model compound for studying the transformation of PFAS. We show that hydrothermal processing in compressed liquid water transforms TFA at relatively mild conditions (T = 150-250 °C, P < 30 MPa), initially yielding gaseous products, such as CHF3 and CO2, that naturally aspirate from the solution. Alkali amendment (e.g., NaOH) promotes the mineralization of CHF3, yielding dissolved fluoride, formate, and carbonate species as final products. Fluorine and carbon balances are closed using Raman spectroscopy and fluoride ion selective electrode measurements for experiments performed at alkaline conditions, where gas yields are negligible. Qualitative FTIR gas analysis allows for establishing the transformation pathways; however, the F-balance could not be quantitatively closed for experiments without NaOH amendment. The kinetics of TFA transformation under hydrothermal conditions are measured, showing little to no dependency on NaOH concentration, indicating that the thermal decarboxylation is a rate-limiting step. A proposed TFA transformation mechanism motivates additional work to generalize the hydrothermal reaction pathways to other PFCAs.

Functional differentiation of olive PLP_deC genes: insights into metabolite biosynthesis and genetic improvement at the whole-genome level.

This study identified 16 pyridoxal phosphate-dependent decarboxylases in olive at the whole-genome level, conducted analyses on their physicochemical properties, evolutionary relationships and characterized their activity. Group II pyridoxal phosphate-dependent decarboxylases (PLP_deC II) mediate the biosynthesis of characteristic olive metabolites, such as oleuropein and hydroxytyrosol. However, there have been no report on the functional differentiation of this gene family at the whole-genome level. This study conducted an exploration of the family members of PLP_deC II at the whole-genome level, identified 16 PLP_deC II genes, and analyzed their gene structure, physicochemical properties, cis-acting elements, phylogenetic evolution, and gene expression patterns. Prokaryotic expression and enzyme activity assays revealed that OeAAD2 and OeAAD4 could catalyze the decarboxylation reaction of tyrosine and dopa, resulting in the formation of their respective amine compounds, but it did not catalyze phenylalanine and tryptophan. Which is an important step in the synthetic pathway of hydroxytyrosol and oleuropein. This finding established the foundational data at the molecular level for studying the functional aspects of the olive PLP_deC II gene family and provided essential gene information for genetic improvement of olive.

Efficient removal of heavy metals from sewage sludge using a low-cost protic ionic liquid: Investigation of mechanism and ecological risk

Land utilization for the disposal of sewage sludge (SS) is an effective strategy, yet the existence of heavy metals (HMs) in the SS represents critical constraints to its implementation on a larger scale. By the principles of simple synthesis steps and low synthesis cost, a low-cost double cationic protic ionic liquid was produced in this study for HMs removal from SS. The influence of reaction time, protic ionic liquid to SS mass ratio, and reaction temperature on HM removal were thoroughly investigated. This result indicated that the integration of protic ionic liquid and heat treatment was efficacious in the efficient elimination of HMs. Under 60°C, 15 min, and protic ionic liquid: SS of 0.5, the removal efficiency of Zn, Fe, Ni, and Cd exceeded 80%, and Cr achieved a removal efficiency of up to 93%. The BCR sequential extraction procedure and calculation of the potential ecological risk index revealed a significant reduction in the ecological risk associated with the treated SS, transitioning from a high to a low-risk level. The alterations in elemental and chemical bonding within the solid phase of SS and changes in polysaccharide and fluorescence properties within the liquid phase of SS were investigated using redundancy analysis, two-dimensional correlation analysis, and parallel factor analysis. These findings suggest that dehydration, deamination, and decarboxylation reactions may be responsible for removing HMs within SS. These findings have a positive impact on further elucidating the effects of protic ionic liquid in SS pretreatment, thereby facilitating the efficient utilization of municipal SS resources.

Synthesis of transition metal-doped ETS-10 zeolite: Effect of the metal addition on the crystallization and morphology and their catalytic application for organic transformation

The crystallinity and morphology of the zeolites have a significant effect on their catalytic performance. Herein, the influence of the introduced metal and copolymer in the synthesis gel on the crystallinity and morphology of the synthesized M-ETS-10 (M=Fe, Co, Ni, Cu) zeolites and on their catalytic activity were investigated. The crystallinity (110%) of the M-ETS-10 (M=Fe, Co, Ni, Cu) was enhanced; the morphology of Fe(or Co)-ETS-10 was changed to imperfect tetragonal bipyramidal shapes, and Ni(or Cu)-ETS-10 turned into irregular large particles consisted of defective tetragonal bipyramidal. Incorporating copolymer into the gel contributed to all the hierarchical M-ETS-10-H being present multi-layered structure consisted of nanosheets. The hierarchical Cu-ETS-10-H exhibited superior catalytic activity than M-ETS-10-H and Cu-ETS-10 in the C–C bond cleavage and decarboxylative hydrosulfonylation reactions. This was attributed to the presence of Lewis basic sites, reversible transformation of Cu2+ to Cu+, as well as the hierarchical pore structure.

Influence of molybdenum incorporation on the structural, chemical, and catalytic properties of iron cobaltite and cobalt ferrite catalysts

In this study, molybdenum doped iron cobaltite and cobalt ferrite catalysts were prepared by coprecipitation, and their structural, morphological, and optical, properties were evaluated by XRD, BET, SEM, FTIR, Raman, XPS and UV–VIS techniques. Their catalytic behavior evaluated in the malic acid oxidative decarboxylation reaction underlined the importance of the incorporation of Mo into the structure of iron cobaltite and cobalt ferrite catalysts. The catalysts with the highest molybdenum content forming cobaltite and iron molybdate phases showed better activity, with cobaltite-based catalysts being more active than ferrite-based ones.

Quinoline-Linked COF for the Photocatalytic Oxidative Decarboxylation and Homo-Coupling Reactions

Quinoline-Linked COF for the Photocatalytic Oxidative Decarboxylation and Homo-Coupling Reactions

Immobilized transition metal (II) bis–imine chelate on ZnO@TiO2 nanoparticles as sufficient catalysts for alcohol oxidation and for α,β‐cinnamic acid decarboxylative bromination

Based on the strong coordination ability of substituted imines towards transition metals of different oxidation states, the coordination of the HL imine ligand with the Cu2+ ion to form the Cu–bis–imine complex was achieved in 2:1 molar ratios. Their structures were confirmed with various spectroscopic tools. Heterogeneously, CuL2 was successfully appended on ZnO@TiO2 nanoparticles, as the less harmful materials, within the deprotonated p‐hydroxy chain of the bonded ligand in CuL2. The surface and internal structural morphologies of ZnO@TiO2@CuL2 were analyzed using X‐ray diffraction (XRD), field‐emission scanning electron microscopy (FESEM), high‐resolution transmission electron microscopy (HRTEM), energy‐dispersive X‐ray spectroscopy (EDS), and infrared (IR) spectroscopy, in addition to thermogravimetric analysis (TGA). The catalytic behavior of both catalysts, CuL2 (the homogeneous catalyst) and ZnO@TiO2@CuL2 (the heterogeneous catalyst), was examined in the benzyl alcohol redox protocols using H2O2 for their optimization. α,β‐Cinnamic acid decarboxylative bromination in the presence of potassium bromide and H2O2 in water was studied with both catalysts, in which (2‐bromovinyl)benzene was the chemoselective product. Both Cu catalysts displayed appreciable catalytic effectiveness for the oxidation protocols and the decarboxylative bromination reactions. CuL2 recorded less required time for optimization than that of the heterogeneous catalyst. The catalytic effectiveness of CuL2 was less promoted than that of ZnO@TiO2@CuL2. Despite the less performance in yield of benzaldehyde for the oxidation protocols with ZnO@TiO2@CuL2, ZnO@TiO2@CuL2 had more recycling than its homogeneous counterpart, with seven to three times, respectively.

Syntheses of α-monofluoroalkyl acetophenones from fluoroalkyl carboxylic NHPI esters and silyl enol ethers by photocatalytic decarboxylative reaction

A photoredox-catalyzed decarboxylative α-monofluoroalkylation of silyl enol ethers with fluoroalkyl carboxylic N-(hydroxy)phthalimide esters has been successfully developed. Diverse functionalized α-monofluoroalkyl acetophenones were produced in modest to good yields under mild and operationally simple conditions. The developed method was further applied to synthesize antalgic and ataractic activity compound containing α-monofluoroalkyl acetophenone skeleton.

Insights into the transformation of natural organic matter during UV/peroxydisulfate treatment by FT-ICR MS and machine learning: Non-negligible formation of organosulfates

Natural organic matter (NOM) is a major sink of radicals in advanced oxidation processes (AOPs) and understanding the transformation of NOM is important in water treatment. By using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) in conjunction with machine learning, we comprehensively investigated the reactivity and transformation of NOM, and the formation of organosulfates during the UV/peroxydisulfate (PDS) process. After 60 min UV/PDS treatment, the CHO formula number and dissolved organic carbon concentration significantly decreased by 83.4 % and 74.8 %, respectively. Concurrently, the CHOS formula number increased substantially from 0.7 % to 20.5 %. Machine learning identifies DBE and AImod as the critical characteristics determining the reactivity of NOM during UV/PDS treatment. Furthermore, linkage analysis suggests that decarboxylation and dealkylation reactions are dominant transformation pathways, while the additions of SO3 and SO4 are also non-negligible. According to SHAP analysis, the m/z, number of oxygens, DBE and O/C of NOM were positively correlated with the formation of organosulfates in UV/PDS process. 92 organosulfates were screened out by precursor ion scan of HPLC-MS/MS and verified by UPLC-Q-TOF-MS, among which, 7 organosufates were quantified by authentic standards with the highest concentrations ranging from 2.1 to 203.0 ng L‒1. In addition, the cytotoxicity of NOM to Chinese Hamster Ovary (CHO) cells increased by 13.8 % after 30 min UV/PDS treatment, likely responsible for the formation of organosulfates. This is the first study to employ FT-ICR MS combined with machine learning to identify the dominant NOM properties affecting its reactivity and confirmed the formation of organosulfates from sulfate radical oxidation of NOM.

Highly efficient one-component benzylidene cyclopentanone initiators for visible light polymerization

Visible light polymerization is a development trend in the field of photocuring. However, most of the reported visible light photoinitiators (PIs) are two-component systems that display limited initiation efficiency due to diffusion restriction and back electron transfer effect. In this study, two one-component visible light PIs (BDNPG-1 and BDNPG-2) are synthesized through combining N-phenylglycine (NPG) moiety with cyclopentanone moiety together. Upon irradiation of blue or green light, they can undergo intermolecular electron transfer followed by proton transfer plus a decarboxylation reaction to produce carbon dioxide and aminoalkyl radicals. This decarboxylation reaction is irreversible so that the intermolecular back electron transfer can be effectively blocked, resulting in a significantly improved photoinitiation efficiency of BDNPG-1 and BDNPG-2 compared with their prototype PI (BDEA) containing no NPG group and the two-component system of BDEA+NPG. Furthermore, both of them have strong two-photon absorption capability and show excellent performance in two-photon polymerization.

Reconsidering lab procedures for hydrothermal carbonization of biomass: The impact of pre-drying and stirring

Although industrial hydrothermal carbonization (HTC) uses wet feedstock, lab-scale studies tend to dry the feedstock under the assumption that the rehydration of the feedstock would restore its original properties. To the best of our knowledge, this assumption has not been thoroughly examined at the lab scale; therefore, its investigation is crucial to prevent any discrepancies that might affect the upscaling of HTC. This research aims to examine the effects of pre-drying biomass by comparing it to the use of wet biomass in HTC experiments, employing three different types of biomass (rejected tomatoes, rejected apples, and digestate). Additionally, the study investigates the influence of stirring on pre-dried and wet biomass under the selected HTC conditions. The results indicate a substantial disparity in studied hydrochar properties when using pre-dried biomass compared to wet biomass. For pre-dried biomass, there is a tendency for an increase in mass yield and solid carbon yield in most examined samples (5–10% dry basis) compared to the wet biomass. Regarding functional groups, wet tomatoes and apples exhibit more pronounced peaks than pre-dried samples. Conversely, digestate shows similar spectra across all examined scenarios. The effect of stirring appears insignificant for most of the studied scenarios; nevertheless, it reduced dehydration and decarboxylation reactions during HTC.

Catalytic Asymmetric Synthesis of α-Mono and α,α-Disubstituted 5- and 6-Membered α-Aza-lactams

AbstractFive- and six-membered cyclic amide structures with an embedded endocyclic α-aza group (α-aza-lactams) not only represent masked or protected forms of α-amino acids, but also form the core of other medicinally relevant compound families such as (thio)hydantoins and di(tri)ketopiperazines. In recent years, catalytic methods have been discovered to synthesize these molecular scaffolds, particularly those bearing an α-stereogenic tri- or tetrasubstituted carbon center, enantioselectively. The wide variety of methods and catalytic activation strategies that have been successfully applied to this end in a short period of years is notable. This short review covers the most significant, highlighting their differences and complementarities. The methods are organized according to the disconnection approach to the target α-aza-lactam structure, which in most cases is deeply bound to the type of catalysis applied.1 Introduction2 Catalyst-Controlled Cα–H Functionalization (Approach a)3 Decarboxylative α-AAA Reactions (Approach b)4 Cα–X Substitution Reactions (Approach c)5 De Novo Synthesis from Acyclic Precursors (Approach d)6 Hydrogenation of (Addition to) α-Alkyliden-α-aza-lactams (Approach e)7 Kinetic Resolution and Deracemization (Approach f)8 Conclusions