Carboxylate Form Research Articles

Computational Study of the Gas-Phase Thermal Degradation and the Reaction Rate Coefficients of Perfluoroalkyl Ether Carboxylic Acids.

Perfluoroalkyl ether carboxylic acids (PFECA), which are replacements for legacy per- and polyfluorinated alkyl substances (PFAS), exhibit undesirable properties and often require thermal remediation. Detailed kinetic evaluation of the pyrolysis of PFECA was achieved computationally using density functional ωB97xD/6-311+G (d,p) to establish homolytic bond dissociation energies for the carboxylic acid and carboxylate forms of ∼90-100 kcal/mol and as low as 65 ± 3 kcal/mol, respectively. The negatively charged oxygenated radical products collapse with activation energies (Ea) of Ea(β-scission) ∼ 12-42 kcal/mol, Ea(1,2-F-shift) ∼ 24-47 kcal/mol, and Ea(oxygen atom-shift) ∼ 33-35 kcal/mol and enthalpies (ΔH) of ΔH(F-loss) ∼ 56-71 kcal/mol. The perfluoroalkoxyl radical intermediates transform via Ea(β scission) ∼ 2-9 kcal/mol and Ea(F-loss) ∼ 25-43 kcal/mol. The radical intermediates have lifetimes in the microsecond-to-nanosecond range at 1000 K and 1 atm, with some radicals stable for hours or even days with respect to the unimolecular processes. The results provide new fundamental thermodynamic and kinetic parameters for the partitioning of the degradation pathways of PFECA and establish specific structure-activity relationships of intermediates, leading to the final degradation products. These results are critical for modeling the thermal treatment of PFECA and related PFAS.

Conformational versatility among crystalline solids of L-phenylalanine derivatives.

In this study, we present a new N-derivative of L-phenylalanine with 2-naphthaldehyde (PN), obtained by the Schiff base formation procedure and its subsequent reduction. This compound was crystallized as a zwitterion {2-[(naphthalen-2-ylmethyl)azaniumyl]-3-phenylpropanoate, C20H19NO2}, as an anion in a sodium salt (catena-poly[[diaquasodium(I)-di-μ-aqua] 2-[(naphthalen-2-ylmethyl)amino]-3-phenylpropanoate monohydrate], {[Na(H2O)4](C20H18NO2)·H2O}n), as a cation in a chloride salt [(1-carboxy-2-phenylethyl)(naphthalen-2-<!?tlsb=-0.2pt>ylmethyl)azanium chloride acetic acid monosolvate, C20H20NO2+·Cl-·CH3COOH], and additionally acting as a ligand in the pentacoordinated zinc compound aquabis{2-[(naphthalen-2-ylmethyl)amino]-3-phenylpropanoato-κO}zinc(II), [Zn(C20H18NO2)2(H2O)] or [Zn(PN)2(H2O)], denoted (PN-Zn), with the amino acid derivative in its carboxylate form. Interestingly, both enantiomers of the zinc complex co-exist within the crystalline structure, one constructed by the ligands with the L (or S) configuration and the other with the ligands having the D (or R) configuration, represented as L,L-PN-Zn and D,D-PN-Zn, respectively. Also, in the structure of the zwitterion, the racemate L,D is observed. These results imply that chirality inversion of the amino acid derivative synthesized from enantiomerically pure L-phenylalanine is taking place, a phenomenon known as oscillatory transenantiomerization. The analysis of these crystal structures reveals that they are primarily stabilized through electrostatic interactions assisted by hydrogen bonds. An interesting finding is that the conformation of PN varies along this family: it is unfolded in the zwitterionic and cationic forms, and folded in the anionic form. To evaluate such conformational differences, we propose the use of a dimensionless Shape Factor quantity defined as the Structural Aspect Ratio (SAR), computed from the geometrical features of the parallelepiped that tightly encloses a conformer constructed by rigid spheres. This parameter provides a simple but useful tool to distinguish conformational differences, providing insights that complement traditional structural analyses. The study of the structural features, conformational diversity, chirality and supramolecular properties of these compounds is also supported by density functional theory (DFT) calculations.

Smartphone-based non-invasive detection of salivary uric acid based on the fluorescence quenching of gleditsia sinensis carbon dots.

Asmartphone-based non-invasive method was developedfor salivary uric acid detection using Gleditsia Sinensis carbon dots (GS-CDs). The GS-CDs synthesized by the one-pot hydrothermal method emitted blue fluorescence at a maximum excitation wavelength of 350nm and had good fluorescence stability in the presence of different ions, while showing selectivity to uric acid solution. The ability of uric acid(UA) to quench the fluorescent substances present in the GS-CDs, was confirmed through HPLC-FLD and LC-MS, FTIR and XPS. The results showed that UA reacted with GS-CDs, with a decrease in hydroxyl groups and the formation of carboxyl groups. The fluorescence quenching suggested a possible dynamic quenching mechanism. In addition, a smartphone-based non-invasive detection method was developed for the detection of salivary UA levels, which reflects blood UA levels. This study provides a new perspective on the utilization of GS shells and advances the development of non-invasive testing for UA.

The Oxidation of Nanocellulose from Oil Palm Empty Fruit Bunch (OPEFB) by TEMPO/NaClO/NaBr

One of the largest biomass wastes in Indonesia is oil palm empty fruit bunch (OPEFB), which produces thousands of tons of waste in a year. The value of biomass can be upgraded to nanocellulose-based adsorbents. Cellulose is extracted through three processes: delignification, bleaching, and hydrolysis. In this study, nanocellulose was oxidated with TEMPO (2,2,6- tetramethylpiperidine-1-oxyl radical)/NaClO/NaBr at pH 10 in a temperature room. The influence of oxidizer (NaClO 2, 4, 6, 8, and 10 mmol/gram) and catalysator (NaBr 25, 50, 100, 150, 200 mg/gram) in the formation of carboxylate groups and reaction time was studied. After the pretreatment process, cellulose content in the final product reached 61.8% with a crystallinity index of 58%. With lengths ranging from 127.4 nm to 512 nm and a diameter of less than 20 nm, nanocellulose is classified as cellulose nanofiber. Conductometry titration is used to find the carboxylate group formed on the nanocellulose surface. The highest carboxylate groups were found in 1,600 mmol/gram by adding 20 mmol/gram NaClO. As the addition of oxidants, degradation of nanocellulose occurred, which was indicated by a decrease in nanocellulose weight and shifting of function groups. All the reaction processes happened below 25 minutes, increasing the reaction rate by adding more than 50 mg/gram NaBr.

Computational Study on the Photo‐Induced Antibiotic Activity of an Azoquinolone with Promising Applications in Photopharmacology

AbstractAzocompounds are among the most important group of molecular photoswitches due to their multiple applications in various scientific areas. We studied the thermal and photochemical reactions of an azocompound with photo‐induced antibiotic properties using ab‐initio calculations based on Kohn‐Shan, Spin‐Flip and time‐dependent Density Functional Theory. Our primary goal is to understand the absorption spectra and isomerization pathways governing the molecule's light‐controlled antibiotic activity. The nuclear ensemble approach was used for the most stable trans and cis isomers, and the absorption spectra were calculated and fitted to predict the cis/trans isomer ratios in the carboxylate form, using experimental measurements as a reference. We stablished that rotation is involved in the most favorable cis↔cis and trans↔trans thermal isomerization pathways, while the inversion mechanism is the most likely for cis↔trans isomerizations. We found that the photochemical trans→cis isomerization follows a consistent mechanism across all trans isomers, involving excitation to S2(ππ*), an in‐plane ultrafast internal conversion to S1(nπ*), followed by rotation of the azo bond up to a twisted S1(nπ*)/S0 conical intersection. We used a custom approach to evaluate the most favorable decay pathway from the S1(nπ*)/S0 conical intersections to trans and cis photoproducts using static calculations.

True Dynamics of Pillararene Host-Guest Binding.

Accurate modeling of host-guest systems is challenging in modern computational chemistry. It requires intermolecular interaction patterns to be correctly described and, more importantly, the dynamic behaviors of macrocyclic hosts to be accurately modeled. Pillar[n]arenes as a crucial family of macrocycles play a critical role in host-guest chemistry and biomedical applications. The carboxylated form with 6 or 7 repeating units is of high popularity due to increased solubility and the compatibility between cavity size and drugs. While prefitted transferable force fields are dominantly applied in host-guest modeling, their reliability and accuracy for macrocyclic hosts remain unjustified. In the current work, based on solid numerical evidence about energetics and dynamics, we prove that all transferable force fields fail to provide a correct description of host dynamics for the most popular carboxylated pillararenes. Therefore, all existing simulation reports on this host family could be biased due to the unsuitability of the force-field description. Such huge modeling problems do not occur in other host families that are relatively rigid (e.g., octa acids and cucurbiturils), highlighting the difficulties in modeling pillararene host-guest interactions. To pursue the true picture of the pillararene dynamics and host-guest binding, we fit high-quality molecule-specific parameters for the carboxylated pillararene based on ab initio calculations and perform an exhaustive conformational search of host-guest binding modes with advanced sampling techniques. We provide estimates of binding thermodynamics, report the true dynamic behavior of the WP6 host in the bound and unbound states, and reveal a general multimodal binding behavior of pillararene host-guest complexes. The current work serves as a critical step toward a reliable all-atom description of pillararene host-guest coordination.

CO2‐Promoted Reactions: A Prosperous Strategy for Conversion of Functional Group in Organic Synthesis

AbstractDue to its nontoxic nature, cost‐effectiveness, and natural abundance, carbon dioxide (CO2) is increasingly recognized as a valuable C1 source in organic synthesis. In addition to the building block for molecular construction, the role of CO2 as a promoter or catalyst to enhance reaction rates and selectivity is gaining attention. Acting as a reversible covalent Lewis acid, CO2 can function as an activating group in the transformation of various compounds, such as alcohols and amines, facilitating the dissociation of hydroxyl or activation of amino. It can also modulate the reactivity of nucleophilic reagents, including H2O, N‐heterocyclic carbenes (NHCs), cyanide (CN), and nucleophilic reductants like borohydride (BH4−). When CO2 interacts with these nucleophiles, it can exhibit Brønsted acidity or hydrogen‐bond donating capabilities and can also act as a coordinating ligand to transition metals in its carboxylate form (─CO2−). In this review, we mainly summarize and classify the synthetic applications and mechanistic insights of CO2‐promoted reactions according to different functional groups and bonding types, which include CO2‐promoted functional transformation of alcohols, CO2‐promoted functional transformation of amines; CO2‐promoted reactions in protic solvent; CO2‐promoted reactions via adducts of CO2 and nucleophiles, CO2‐promoted reductive reaction.

Cannabichromene (CBC) Shows Matrix-Dependent Thermal Configurational Stability.

The optical purity of cannabichromene (CBC, 1a) is affected by the matrix in which it is generated by thermolysis from its native carboxylated form (cannabichromenic acid, CBCA, 1b). Thus, thermolysis at 130 °C in planta caused a marked decrease of the enantiomeric excess (ee), while, under the same conditions, only a modest decrease of optical purity was observed when thermolysis was carried out in extracto. To rationalize these puzzling observations, the kinetics of thermal (100 °C) racemization of enantiopure cannabichromene (1a) was evaluated by enantioselective ultrahigh performance liquid chromatography in solvents (decalin and isopropyl alcohol, neat and acidified with TFA) and surfaces (native and silanized borosilicate glass) of complementary polarity. Optical stability was more than halved in isopropanol compared to decalin (t1/2 50 h vs 135 h), but acidification had no effect on racemization. However, contact with a solid surface dramatically accelerated the process, with a t1/2 of only 6 h on both glass surfaces. The overall extent of racemization of enantiopure CBC (1a) was compared under conditions commonly used for decarboxylation (heating at 130 °C) between a decalin solution and a thin film on three different surfaces (native and silanized borosilicate glass and powdered blank cannabis biomass). In line with the kinetic data, a significant erosion of enantiopurity was observed on all solid surfaces compared to the solution. These observations suggest that discrepancies in the reported enantiomeric purity of natural CBC could be not only of biogenetic derivation but also be associated with the decarboxylation protocol of cannabichromenic acid (1b). These findings, while relevant for the exploitation of the bioactivity of natural CBC for human health, should also prompt the adoption of a standardized decarboxylation protocol for the studies on the configurational status of CBC (1a) in cannabis and, in general, of cannabinochromanoids in nature.

Improving wood surface wettability through gas-phase ozone treatment of air-dry wood

An increase in wood free surface energy enhances the wettability of wood surfaces, leading to better interaction with water-based coatings. This study investigated the effect of gas-phase ozonation on the wettability of spruce, thermo-modified pine, and birch woods. The effects of the treatment were evaluated by measuring the water contact angle and the Cobb value on the wood sample surfaces, and by determining the surface free energy of the wood surfaces using the Owens, Wendt, Rabel, and Kaelble (OWRK) calculation method. Furthermore, water absorption and evaporation rates were assessed through water immersion and subsequent drying of the wood samples. The results indicated that ozone treatment increased the surface energy, and especially its polar component, thus accelerating water spreading and absorption on the wood surfaces. The most probable cause of the observed effects is the formation of new carbonyl and carboxyl groups resulting from reactions of the ozone with the wood surface. The findings suggest that the ozone treatment technique can enhance spreading, absorption, and adhesion of water-based adhesives and coatings to wood surfaces. This research may facilitate the development and use of new environmentally friendly water-based adhesives and coatings.

Synthetic Organic Electrochemistry: From Bulk to Nano Chitin

Negatively charged nano chitin with carboxylic groups on the surface are traditionally synthesized by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) mediated oxidation of α-chitin in water at pH 10 with the use of sodium hypochlorite (NaClO) or laccase enzyme as a co-oxidant. However, the use of NaClO leads to environmental concerns, while the laccase-mediated process suffers from notable deceleration due to undesired enzyme adsorption onto the chitin substrate. Therefore, we propose an alternative methodology for the fabrication of nano chitin using an environmentally friendly electrochemical approach.The properties of surface chemistry, crystal structure, and morphology of nano chitin were comprehensively assessed using Zeta analysis, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The size distribution of nano chitin ranged from 700 to 900 nm, with a negative surface charge of approximately -40 mV. Furthermore, new peak appearance at 1730 cm-1 in the FTIR spectrum attributes to the formation of carboxylic groups on the surface of nano chitin.In conclusion, the application of electrochemical methods shows significant potential for the efficient production of nano chitin through TEMPO-mediated oxidation, offering promising avenues for future research and application. Following synthesis, the resultant product undergoes examination to evaluate its emulsification efficacy, particularly in the context of food applications.

The effect of high-energy electron beam irradiation on the physicochemical properties of PET material

The effect of high-energy electron beam irradiation on the physicochemical properties of PET material

Chemical changes from N-doped graphene and Metal-Organic Frameworks to N-G/MOF composites for improved electrocatalytic activity

Chemical changes from N-doped graphene and Metal-Organic Frameworks to N-G/MOF composites for improved electrocatalytic activity

Silver-Tungsten induced codeposition: Influence of pH and carboxylic acid form in a DMH-based electrolyte

Silver-Tungsten induced codeposition: Influence of pH and carboxylic acid form in a DMH-based electrolyte

A molecular mechanism for bright color variation in parrots.

Parrots produce stunning plumage colors through unique pigments called psittacofulvins. However, the mechanism underlying their ability to generate a spectrum of vibrant yellows, reds, and greens remains enigmatic. We uncover a unifying chemical basis for a wide range of parrot plumage colors, which result from the selective deposition of red aldehyde- and yellow carboxyl-containing psittacofulvin molecules in developing feathers. Through genetic mapping, biochemical assays, and single-cell genomics, we identified a critical player in this process, the aldehyde dehydrogenase ALDH3A2, which oxidizes aldehyde psittacofulvins into carboxyl forms in late-differentiating keratinocytes during feather development. The simplicity of the underlying molecular mechanism, in which a single enzyme influences the balance of red and yellow pigments, offers an explanation for the exceptional evolutionary lability of parrot coloration.

Epoxidized cardanol oleate (ECD-OA) as an effective biobased chain extender of polylactic acid (PLA)

Moisture exposure during polyester processing can lead to degradation, resulting in the formation of carboxyl and hydroxyl end-groups. To preserve mechanical properties, thorough drying and the use of chain extenders like epoxy acrylates and isocyanates during extrusion are crucial for maintaining or enhancing molecular weight through in-situ reactions. Our study introduced epoxidized cardanol oleate (ECD-OA), containing epoxy and long-chain alkyl groups, as a potential chain extender, and compared its effectiveness with commercially available epoxidized cardanol glycidyl ether (cardolite NC514). Compared to neat PLA without chain extension, the addition of 1 phr ECD-OA resulted in an increase in the molecular weight (Mw) of PLA from 15.3×104g/mol to 17.1×104g/mol, demonstrating a chain extension efficiency of 11.8%. The melt flow rate of PLA decreased from 9.9g/10min to 5.0g/10min, and the initial thermal degradation temperature of PLA increased by 5.7°C. Upon chain extension, there was a substantial increase in both the elongation at break and tear resistance of the PLA film. The results demonstrate that ECD-OA can extend PLA molecular chains through chemical reactions and promote entanglement with the long alkane chain, consequently enhancing the mechanical and thermal properties of PLA. Due to the enzyme's preference for biobased small molecules, the PLA film with the addition of a biobased chain extender is more prone to enzymatic degradation compared to neat PLA. To conclude, ECD-OA acts as a bio-based chain extender that improves the performance of PLA while also enhancing its biodegradability.

Theoretical investigation on Friedel−Crafts reaction followed by rear-rangement/aromatization or ring-opening delivering benzoheterocycle and polycyclic alcohol, biaryl carboxylic acid

Our DFT calculations provide the first theoretical investigation on CF3SO3H-promoted [1,5]Friedel−Crafts of 2-aryoxy-1,3-indandione and base-facilitated [1,6]Friedel−Crafts of 1,3-dicarbonyl. An intramolecular [1,5]Friedel−Crafts addition took place by activating carbonyl through H bridge with CF3SO3H. The resulting tertiary alcohol underwent dehydration producing reactive carbocation, which instigated a cascade of carbox-yl group formation, ring-opening via C−C bond dissociation and C=C bond formation realizing aromatization. The product 3-aryl-2-benzo was yielded with recovered CF3SO3H. The electron-rich phenoxy group was deprotonated by HO- forming water. The initial nucleophilic addition to spatial-adjacent carbonyl afforded dieneone. It isomerized to the first product polycyclic alcohol. Then carboxylation occurred via hydroxyl shift followed by ring-opening aromatization to the second product biaryl carboxylic acid. The positive solvation effect is suggested by decreased absolute and activation energies in solution compared with in gas. These results are supported by Multiwfn analysis on FMO composition of specific TSs, and MBO value of vital bonding, breaking.

Technological quality improvement of gluten-free dough and chapatti-making by incorporation of modified oat 1,4-β-D-glucan

The present study aimed to explore the contribution of untreated (UtβG) and modified oat 1,4-β-D-glucan (OzβG) to the quality of gluten-free chapattis at varying concentrations (0, 1.5, 3, and 4.5% labelled as M0, M1, M2 and M3 for maize chapattis and F0, F1, F2 and F3 for finger millet chapattis, respectively). The functionality of flours was significantly enhanced by the addition of UtβG and OzβG. However, OzβG incorporated flour exhibited a more pronounced influence on both functional and farinographic parameters when compared to flours with UtβG. Further, the hardness of the chapattis decreased with incorporation of OzβG and it was lowest for M2 and F2 i.e. 6.38N and 5.27N, respectively due to the formation of more carboxyl and hydroxyl groups, which had more affinity towards water molecules. The sensory analysis indicated that OzβG incorporated M2 and F2chapattis exhibited the highest overall acceptability. Hence, this study provides valuable insights into the utilization of UtβG and OzβG for the formulation of gluten-free chapattis with better dough characteristics and chapatti-making properties.

Identification of clerodane diterpene modifying cytochrome P450 (CYP728D26) in Salvia divinorum - en route to psychotropic salvinorin A biosynthesis.

Salvia divinorum is a hallucinogenic plant native to the Oaxaca in Mexico. The active ingredient for psychotropic effects in this plant is salvinorin A, a potent and highly selective κ-opioid receptor agonist. Salvinorin A is distinct from other well-known opioids, such as morphine and codeine, in that it is a non-nitrogenous diterpenoid with no affinity for μ-opioid receptor, the prime receptor of alkaloidal opioids. A terpene opioid that selectively targets a new opioid receptor (κ-opioid receptor) can be instrumental in developing alternative analgesics. Elucidation of the salvinorin A biosynthetic pathway can help bio-manufacture diverse semi-synthetic derivatives of salvinorin A but, to date, only two enzymes in the Salvinorin A pathway have been identified. Here, we identify CYP728D26 that catalyzes a C18 oxygenation on crotonolide G, which bears a clerodane backbone. Biochemical identity of CYP728D26 was validated by in vivo reconstitution in yeast, 1H- and 13C-NMR analyses of the purified product, and kinetic analysis of CYP728D26 with a Km value of 13.9 μM. Beyond the single oxygenation on C18, collision-induced dissociation analysis suggested two additional oxygenations are catalyzed by CYP728D26 to form crotonoldie G acid, although this carboxylic acid form is a minor product. Its close homologue CYP728D25 exhibited a C1-hydroxylation on the clerodane backbone in a reconstituted yeast system. However, CYP728D25 showed no activity in in vitro assays. This result implies that catalytic activities observed from overexpression systems should be interpreted cautiously. This work identified a new CYP catalyst and advanced our knowledge of salvinorin A biosynthesis.

Vanadium-Containing Ionic Liquids Derived from Complexes of Modified Edta as Catalysts of Epoxy-Anhydride Ring-Opening Copolymerization.

A new type of vanadium-containing ionic liquids (ILs) was synthesized by cation exchange from barium salts of oxidovanadium(IV) complexes stabilized by edta and its congeners (dcta, oedta, and heedta) serving as pentadentate ligands. All starting barium salts and several magnesium and cesium salts, serving as models for the cation exchange, were structurally characterized by single-crystal XRD analysis. The synthesized ILs consisting of organic cations (Bu4N+, Bmim+, and Bu4P+) and complex anions ([VO(edta)]2-, [VO(dcta)]2-, [VO(oedta)]-, and [VO(heedta)]-) were characterized by analytical and spectroscopic methods including EPR spectroscopy and cyclic voltammetry. Then, ILs were tested as catalysts for the ring-opening copolymerization of epoxy resin with cyclic anhydride showing significant catalytic activity, which led to production of highly cross-linked glassy thermosets. A detailed isothermal DSC kinetic study was performed for the most promising IL showing that the progress of cross-linking can be successfully fitted by the Kamal-Sourour model. Based on the DSC and NIR results, the initiation mechanism of the cross-linking in the presence of vanadium-containing IL was suggested. IL had ability to activate a rapid hydrolysis of anhydride cycle and the formed carboxyl groups initiated a polyesterification. In parallel, the role of imidazolium cation of IL for the initiation of chain-growth anionic copolymerization is also discussed.

Analysis of the effects of Pr1-xCexCoO3/dolomite catalyst on energy saving and carbon reduction in biomass gasification for the production of hydrogen-rich syngas

Analysis of the effects of Pr1-xCexCoO3/dolomite catalyst on energy saving and carbon reduction in biomass gasification for the production of hydrogen-rich syngas