Carboxylic Acid Solvents Research Articles

Synthesis, crystal structure and Hirshfeld surface analysis of binuclear Cu(II) complexes from o/p-hydroxybenzoic acid with ethanol and water solution of monoethanolamine

The new paddlewheel-like binuclear copper complexes of general formulae [Cu2(o-HBA)4(DMFA)2] (1),[Cu2(o-HBA)4(H2O)2]DMFA (2) and {[Cu2(o-HBA)2(p-HBA)2(H2O)2]EtOH}{[Cu2(o-HBA)4(H2O)2]}, (3) (o/p-HBA = ortho/para-hydroxybenzoic acid, DMFA = Di-methylforamide) have been obtained by the reaction in ethanol, water and water: ethanol solution of MEA (monoethanolamine) and freshly prepared copper hydroxide with o-HBA (for 1 & 2) and o/p-HBA (for 3) respectively. Each ligand was bonded through two oxygen atoms to the metals from a carboxylic acid group and solvent (DMFA/water) was bonded with each Cu (II) atom at axial position by oxygen atoms. Complex-3 was followed in a somewhat different manner by linking two dinuclear Cu(II) complexes through water molecules using hydrogen bonds. Hirshfeld analysis of both complexes was determined and the results indicated that percentage of interaction, the H···H contacts were about 43, 38.5 and 40.5% for complexes 1, 2 and 3 respectively and the percentage of other interactions was significantly lower than these.

Enhanced thermal stability and oxygen storage capacity of ceria-zirconia prepared by flame spray pyrolysis under high temperature

Ceria zirconia solid solution with high oxygen storage capacity (OSC) and thermal stability under 1000 ​°C is quite important for support materials in three-way catalysts (TWCs). In this work, Ce1-xZrxO2 with different Zr dopants (x ​= ​0, 0.125, 0.250 and 0.375) have been prepared by flame spray pyrolysis (FSP) with carboxylic acid or ethanol and carboxylic acid (v:v 1:4) solvents. The influences of Zr content and the addition of ethanol into carboxylic acid on the OSC performance and thermal stability have been systematically characterized by X-ray diffraction (XRD), N2 adsorption-desorption, Raman analysis, field emission scanning electron microscope (FESEM), high resolution transmission electron microscope (HRTEM), X-ray photoelectron spectroscopy (XPS), hydrogen-temperature programmed reduction (H2-TPR), and pulse thermal analysis using H2 as reducing agent. The presence of cubic-tetragonal interfaces in the Ce0.750Zr0.250O2 sample can enhance the formation of oxygen vacancies and the mobility of lattice oxygen in ceria-zirconia solutions, which results in the largest OSC (349 ​μmol ​g−1) among the fresh samples. The cubic-tetragonal interfaces in the Ce0.750Zr0.250O2 sample can also promote the thermal stability under 1000 ​°C to preserve better OSC (202 ​μmol ​g−1) than other aged samples. Furthermore, after adding with ethanol into carboxylic acid solvent, the OSC of the sample further increases to 371 ​μmol ​g−1 for the increment of oxygen vacancy concentration. It is worthy to note that the introduction of ethanol can suppress Zr migration from the lattice to the surface of CeO2 at high temperature, further enhancing OSC (240 ​μmol ​g−1) and thermal stability.

Measurement and correlation of the solubility of 3-methoxybenzoic acid in fourteen mono-solvents at temperatures from 278.15 K to 323.15 K

A gravimetric method was used to determine the equilibrium solubility of 3-methoxybenzoic acid (3MBA) in 14 kinds of organic mono-solvents (methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, sec-butanol, formic acid, acetic acid, ethyl formate, methyl acetate, ethyl acetate, iso-propyl acetate, butyl acetate) from 278.15 K to 323.15 K at 0.1 MPa. In all the solvent systems studied, the solubility increases monotonously with the increasing of temperature. In addition, the effect of solvent properties on solid–liquid equilibrium of 3MBA was investigated. The results show that dissolving process of 3MBA in solvent is a complex process, which is affected by the action of solvent properties; Correlation analysis found that the solvent properties containing hydrogen bond donation (α), hydrogen bond acceptance (β), polarity index (ET30), Hildebrand solubility parameter (δH), cohesive energy density and surface tension process great influence on the dissolving behavior of 3MBA. And then, topological index (H) which can reflect the molecular structure information of the solvents was calculated. It was found that the solubility of 3MBA decreased with the increasing of H values in alcohol and ester solvents, and increased with the increasing of H values in carboxylic acid solvents. Besides, the solubility of 3MBA were related to the modified Apelblat model, λh model, van’t Hoff model and NRTL model, and the modified Apelblat model gave the best correlation results, with the ARD% of 0.68%. In addition, COSMO-RS model was used to calculate the σ-profiles and solvation free energy of selected solute–solvent systems, σ-profiles analysis was qualitatively described the intermolecular interaction, it was found that the solubility of 3MBA in the selected solvents was correlated with the solute–solvent intermolecular interactions; Solvation free energy was calculated in the “Molar” framework and found that the solubility of 3MBA in alcohols, esters and carboxylic acids decreased with the decreasing of the absolute value of the solvation free energy.

Catalytic Oxidative-Extractive Deep Desulfurization of Diesel Fuel by N-methyl-2-pyrrolidone-Based Protic Acidic Ionic Liquids (PAILs)

Inexpensive and low-viscosity Protic Acidic Ionic Liquids (PAILs) of N-metheyl-2-pyrrolidone formate, acetate, and propionate abbreviated as [Hnmp][HCOO], [Hnmp][CH3COO] and [Hnmp][CH3CH2COO] respectively, were prepared and characterized by FT-IR and H-NMR. Deep oxidative and extractive desulfurization of a simulated oil and a real diesel containing 1000 ppmw sulfur were studied under the catalysis of the proposed PAILs without additional carboxylic acid and extraction solvent in the system. The desulfurization efficiency in this study was influenced by both amounts of PAILs and concentration of the produced peroxy acids from H2O2. Comparing to [Hnmp][HCOO], [Hnmp][CH3COO] and [Hnmp][CH3CH2COO] had a relatively higher extraction ability however the weaker acidic properties of them resulted in a lower activation of H2O2 to produce peroxy acids and finally led to lower oxidative desulfurization (ODS) efficiency in the same condition. Additionally, the neutralization reaction may not be efficiently gone to the right hand by weaker acids. The effects of the main process variables were studied in detail. The highest desulfurization yield of 97% for BT and 99% for DBT and 4,6-DMDBT, were achieved using [Hnmp][HCOO] in the ODS system at a temperature of 40 °C, H2O2/sulfur molar ratio of 10, VPAIL/Voil of 0.2, and a reaction time of 90 min. The immiscibility of the proposed PAILs in this study with the oil phase caused the easy separation of them after desulfurization. The possible ODS pathway was also proposed.

Shape engineering of palladium aerogels assembled by nanosheets to achieve a high performance electrocatalyst

Three-dimensional noble metal aerogels are unique solid materials with ultralow densities, large open pores, and high surface areas. Despite several research works on noble metal aerogels assembled by nanochains, the investigation of noble metal aerogels assembled by nanosheets has not been reported to date. In this work, palladium aerogels assembled by nanosheets have been synthesized in four various carboxylic acid (RCOOH) solvents with different alkyl groups (R= H– (formic acid, FA), CH3– (acetic acid, AA), CH3CH2– (propionic acid, PA), and CH3CH2CH2– (butyric acid, BA)). It has been found that the R groups play a crucial role in the morphology of palladium aerogels so that the Pd aerogels synthesized in acetic acid and propionic acid solvents show better morphology than that of palladium aerogels synthesized in formic acid and butyric acid solvents. The electrocatalytic activity and durability of all aerogels are evaluated using cyclic voltammetry (CV) and chronoamperometry (CA) experiments toward ethanol oxidation. Based on CV and CA data, Pd aerogels synthesized in AA and PA show high catalytic activity and durability due to their unique structures.

Metal-Free Halogen(I) Catalysts for the Oxidation of Aryl(heteroaryl)methanes to Ketones or Esters: Selectivity Control by Halogen Bonding.

Metal-free halogen(I) catalysts were used for the selective oxidation of aryl(heteroaryl)methanes [C(sp3 )-H] to ketones [C(sp2 )=O] or esters [C(sp3 )-O]. The synthesis of ketones was performed with a catalytic amount of NBS in DMSO solvent. Experimental studies and density functional theory (DFT) calculations supported the formation of halogen bonding (XB) between the heteroarene and N-bromosuccinimide, which enabled imine-enamine tautomerism of the substrates. No additional activator was required for this crucial step. Isotope-labeling and other supporting experiments suggested that a Kornblum-type oxidation with DMSO and aerobic oxygenation with molecular oxygen took place simultaneously. A background XB-assisted electron transfer between the heteroarenes and halogen(I) catalysts was responsible for the formation of heterobenzylic radicals and, thus, the aerobic oxygenation. For selective acyloxylation (ester formation), a catalytic amount of iodine was employed with tert-butyl hydroperoxide in aliphatic carboxylic acid solvent. Several control reactions, spectroscopic studies, and Time-Dependent Density Functional Theory (TD-DFT) calculations established the presence of acetyl hypoiodite as an active halogen(I) species in the acetoxylation process. With the help of a selectivity study, for the first time we report that the strength of the XB interaction and the frontier orbital mixing between the substrates and acyl hypoiodites determined the extent of the background electron-transfer process and, thus, the selectivity of the reaction.

D-A type sensor array for differentiation and identification of white wine varieties based on specific solvent effect activated by CT-LE transition

In this work, we synthesize a series of compounds with electron donor (D) and acceptor (A) units. They show general solvent effect in aprotic solvents, suggesting a charge transfer (CT) process. While in protic solvents including water, ethanol and methanol, the spectra exert no polarity-dependence but a remarkable hypochromatic shift together with the fading of CT band. Dynamic analysis implies that intermolecular hydrogen bond will be formed between carboxylic acid and protic solvent, boosting another deactivation pathway that jumps off a bigger energy gap, in other words, favoring the locally excited (LE) state emission. The CT-LE transition involves variations in both absorption and emission spectra, and further poses competition with other mechanisms including activated/restricted intramolecular rotation (IR/RIR). Inspired by the cross-reactivity, we turn our attention to the development of sensor array, in order to identify white wine varieties. The differential spectral responses are recorded, generating multiple factors including absorption wavelength (λab), emission wavelength (λem), absorbance (Abs.) and emission intensity (Int.). These factors are processed with principal component analysis (PCA), creating a three-dimensional fingerprint data base for white wines. The data points in the coordinate system are clustered into 10 different groups, demonstrating a clear differentiation of all the white wines. More importantly, as our final test for whether the sensor array can identify the counterfeits, an adulterated liquor sample, which is provided by police officers, is fingerprinted on the three-dimensional diagram. Its canonical factors fall into an area distinct from the adulterated wine, indicating a clear identification.

Cu‐Mediated Direct Aryl CH Halogenation: a Strategy to Control Mono‐ and Di‐Selectivity

AbstractA protocol for the copper‐mediated direct aryl CH halogenation is presented. Highly selective mono‐ and di‐halogenations are achieved by using acyl hypohalites, generated in situ from the readily available carboxylic acid and N‐halosuccinimides (NXS; X=Br and Cl) as powerful halogenating reagents. The correct choice of carboxylic acid additives and solvents is essential for both high yield and selectivity. Consequently, the use of inexpensive Cu catalyst and the new strategy for the in situ generation of acyl hypohalite halogenating reagents from the readily affordable and easily‐to‐handle carboxylic acid and NXS (X=Br and Cl) offers advantages for practical application.

ChemInform Abstract: Pd(II)‐Catalyzed Primary‐C(sp3)—H Acyloxylation at Room Temperature.

AbstractThe direct diacetoxylation is feasible [cf.(XII)].

Pd(II)-Catalyzed Primary-C(sp3)–H Acyloxylation at Room Temperature

With the aid of a novel S-methyl-S-2-pyridyl-sulfoximine (MPyS) directing group (DG), the unactivated primary β-C(sp(3))-H bond of MPyS-N-amides oxidizes at room temperature. The catalytic conditions are applicable to the diacetoxylation of primary β,β'-C(sp(3))-H bonds, and the carboxylic acid solvent is pivotal in the formation of the C-O bond. The MPyS-DG cleaves from the oxidation products and is recovered. This method provides convenient access to α,α'-disubstituted-β-hydroxycarboxylic acids.

Extraction of ethanol with higher carboxylic acid solvents and their toxicity to yeast

In a screening exercise for ethanol-selective extraction solvents, partitioning of ethanol and water from a 5 wt% aqueous solution into several C8–C18 carboxylic acids was studied. Results for the acids are compared with those from alcohols of similar structure. In all cases studied, the acids exhibited higher separation factor, but lower capacity than their alcohol analogs. Solvent toxicity to a commercial yeast commonly used in fuel ethanol production was evaluated for selected solvents. For the acids studied, those containing 12 or fewer carbons were toxic or inhibitory to the yeast; those containing 16 or more carbons were non-toxic and non-inhibitory.

Key Technology for Extraction, Thermoplastic Modification and Application of Lignin

New technique has been used to extract of lignin by adding carboxylic acid derivates and organic solvent to precipitate and extract lignin from black liquor (pulp wastewater). Through this new treatment process, new carboxylate which is decomposed to carbondioxide, water and metal oxide at the high temperature was formed. The process of using organic carboxylic acid and organic solvent to precipitate and extract lignin is low-cost and can not cause second pollution. The lignin obtained through this new process is water insoluble and thermoplastic. Its weigh average molecular weight, purity, and glass transition temperature are higher than 2000, 90% and 150°C, respectively. Through the methods of thermoplastic modification, the thermoplastic properties for high purity lignin-based composite materials are improved significantly. Its melt flow ratio, tensile strength and elongation at break are 0.73 g/10 min, 11.8 MPa, and 21%, respectively. Thermoplastic lignin-based composite materials have good processing properties as well as synthetic polymers for extruding, injection molding, and blowing processes. Lignin, as a kind of natural thermoplastic polymers with good processing properties, can be carried out to process for film, foam, and thermoplastic composite.

Tetraaquabis[3-(4-carboxyphenoxy)propionato-κO]copper(II) dihydrate

The title compound, [Cu(C10H9O5)2(H2O)4]·2H2O, is a neutral mononuclear complex. The CuII ion, which lies on an inversion center, displays an octa­hedral coordination geometry defined by two carboxyl­ate O atoms of two different 3-(4-carboxy­phen­oxy)propionate ligands and four water mol­ecules. The crystal structure is stabilized through strong O—H⋯O hydrogen bonds involving uncoordinated carboxylic acid groups, and coordinated and solvent water mol­ecules, leading to a three-dimensional network. The O⋯O separations range from 2.623 (3) to 2.909 (3) Å and O—H⋯O angles range from 163 (4) to 179 (4)°.

Complexity in the Self-Assembly of Bifunctional Molecules on HOPG: The Influence of Solvent Functionality on Self-Assembled Structures

Self-assembled monolayers of bifunctional molecules HOOC(CH2)nCOOH (n = 20, 18, 16, 14, 12, 10), HOOC(CH2)nCH2OH (n = 13, 14), and HOCH2(CH2)14CH2OH dissolved in octanoic acid were investigated using scanning tunneling microscopy, to understand the self-assembly of bifunctional molecules and the influence of a carboxylic acid solvent on the formation of self-assembled structures on HOPG. In the series of di-acids (HOOC(CH2)nCOOH), only HOOC(CH2)20COOH forms stable coadsorption structures with the solvent octanoic acid. The remaining di-acids form stable single-component monolayers and do not coadsorb with solvent octanoic acid. Coadsorption structures involving mixtures of di-acids were observed. This result suggests that coadsorption with acid solvent or with other di-acids occurs to maximize hydrogen-bond density in the overlayer. A quantitative model based on this concept is proposed. For hetero-bifunctional molecules HOOC(CH2)nCH2OH (n = 13, 14), the coadsorption of HOOC(CH2)14CH2OH and octanoic acid at the molecular level produces a microscopic mesh made of homogeneously arranged openings with a dimension of approximately 12.5 A x approximately 5.0 A x approximately 1.8 A. For the hetero-bifunctional molecule HOOC(CH2)13CH2OH, hydroxyl groups of two adjacent lamellae assemble to form a herringbone geometry, and the two carboxylic acid groups assemble with a straight head-to-head configuration. In addition, a new mixed hydrogen-bonding network of COOH...O-H was observed in another self-assembled structure of this molecule. The bifunctional molecule HOCH2(CH2)14CH2OH exhibits multiple packing patterns on HOPG via different hydrogen-bonding networks. HOCH2(CH2)14CH2OH self-assembles using the H-O...O-H network typical of the n-alcohol herringbone structure, forming an asymmetric adsorbate on HOPG. It also forms domains with another hydrogen-bonding network, in which molecules in adjacent lamellae are parallel to each other. This investigation demonstrates the complexity and diversity of self-assembled structures formed from bifunctional molecules on solid surfaces. It also indicates that a solvent with the same functional group as the solute can significantly impact the formation of the self-assembled structures of these bifunctional molecules.

Competition and Coadsorption of Di-acids and Carboxylic Acid Solvents on HOPG

The self-assemblies of di-acids HOOC-(CH(2))(n)-COOH (n = 20, 18, 16, 14, 12, 10) in three solvents hexanoic acid, octanoic acid, and decanoic acid on highly oriented pyrolytic graphite (HOPG) were studied with scanning tunneling microscopy (STM). In the solvent hexanoic acid, solvent molecules coadsorb with HOOC-(CH(2))(n)-COOH (n = 20, 18, 16) via formation of hydrogen bonds. The solvent octanoic acid coadsorbs with HOOC-(CH(2))(n)-COOH (n = 20, 18). Decanoic acid only coadsorbs with HOOC-(CH(2))(20)-COOH. In each solvent, the trend of coadsorption between solvent molecules and di-acid molecules decreases with decreasing chain-length of di-acid molecules. These systematic investigations suggest that coadsorption of solvent molecules with di-acid solute molecules is mainly dependent on the relative hydrogen-bond densities in the formed monolayer. This is consistent with the maximization of adsorption heat of the self-assembled monolayers of di-acids dissolved in solvents of carboxylic acids.

Polyion Complex Nanofibrous Structure Formed by Self‐Assembly of Chitosan and Poly(acrylic acid)

AbstractSummary: An ideal scaffold design has a nanofibrous structure that can replace the natural extracellular matrix (ECM) until host cells can repopulate and resynthesize a new natural matrix. In this study, chitosan (CS)‐poly(acrylic acid) (PAA) nanofibers with diameters that range from 50 to 150 nm are synthesized successfully by a modified dropping method. Exactly how various carboxylic acid solvents affect the formation of CS‐PAA nanofibrous complex is also discussed. The results show that using adipic acid as a solvent to dissolve CS, adjusting the final pH value of the CS solution to 3, and then dropping the CS solution into the PAA solution at a ratio of 3:1, cause a significant reaction of CS with PAA and the nanofibers are dispersed uniformly. After freeze‐drying, a 3‐D interconnected CS‐PAA nanofibrous scaffold with a fiber diameter that ranges from 50 to 200 nm can be obtained. The CS‐PAA nanofibrous matrix is of particular interest in tissue engineering for controlled drug release and tissue remodeling.Nanofibrous structure via polyion complex formation between chitosan and poly(acrylic acid).imageNanofibrous structure via polyion complex formation between chitosan and poly(acrylic acid).

Synthesis and characterization of novel tricarboxylatoplatinum(IV) complexes. Nucleophilic substitution of (diamine)-tetrahydroxoplatinum(IV) with carboxylic acid

The reaction of [Pt(IV)(dach)(OH) 4] (dach= trans-(±)-1,2-diaminocyclohexane) with an excess of carboxylic acid at room temperature afforded tricarboxylatoplatinum(IV) complexes, [Pt(dach)(L) 3(OH)] (L=acetato, propionato, valerato) in contrast to the carboxylation reaction with excess carboxylic anhydrides, which gave only tetracarboxylatoplatinum(IV) complexes as a major product. The protonation on hydroxo ligand of the platinum(IV) complex to form aqua ligand seems to be followed by nucleophilic substitution by carboxylate or chloride anion. Such nucleophilic substitution afforded only partially substituted tricarboxylatoplatinum(IV) complexes in carboxylic acid solvent whereas the reaction in 0.1 M HCl solution gave tetrachloroplatinum(IV) complex. This difference is explainable by different p K a values of the four aqua ligands, among which the last aqua ligand may have sufficiently low p K a value allowing the protonation only in strong acidic media like hydrochloric acid.

Chirality-Memory Molecule: Crystallographic and Spectroscopic Studies on Dynamic Molecular Recognition Events by Fully Substituted Chiral Porphyrins

X-ray crystallography of a mandelate complex of a D2-symmetric saddle-shaped porphyrin such as 2,3,7,8,12,13,17,18-octamethyl-5,15-bis(2‘,6‘-dimethoxyphenyl)-10,20-diphenylporphyrin (2) showed that two mandelate anions are hydrogen bonded to the pyrrole NH moieties in a monodentate fashion, where the absolute structure of the porphyrin macrocycle is determined in such a way that the least hindered section of the host molecule accommodates the phenyl group of the mandelate. IR and 1H NOESY NMR spectroscopies in CH2Cl2 indicated that a similar binding mode is operative in solution. A series of fully substituted chiral porphyrins having different numbers of o-dimethoxyphenyl groups at the meso-positions (1−3) showed different chiral transfer efficiencies and ring inversion activities. Thermal racemization profiles of protonated 2 in a variety of achiral carboxylic acids indicated that the ring inversion rate is dependent on the steric factor as well as the acidity of the carboxylic acid solvent.

Unique solvent properties of straight-chain carboxylic acids for electron-transfer photoreactions

We have studied the electron-transfer fluorescence quenching of pyrene by diphenyliodonium cation in a series of straight-chain carboxylic acid solvents. Use of the Py-scale of solvent polarity suggests specific solvation of the pyrene by the polar head groups of the acid solvents. We hypothesize involvement of hydrogen bonding between the carboxyl functions and the π-electron cloud of pyrene. Electron-transfer quenching of pyrene fluorescence by diphenyliodonium cation is, surprisingly, not diffusion controlled. From experimental data we have estimated values for the bimolecular reaction rate constant, k r, in each solvent over the temperature range 20–60°C, and calculated, therefrom, reorganization energies. We find that λ is more-or-less independent of acid chain length. We, therefore, infer that the head groups or the carboxylic acids are principally involved in solvent relaxation, and propose that a relaxation mechanism involving rupture (or formation) of hydrogen bonds is most likely.

Mechanistic aspects of benzylic bromide formation and oxidation during the cobalt acetate bromide catalyzed oxidation of alkylbenzenes in carboxylic acids

The formation and fate of benzylic bromides during the cobalt acetate bromide catalyzed oxidation of toluene and 4-chlorotoluene were investigated in carboxylic acid solvents. The rate of formation of benzylic bromides depends on the substrate and catalyst concentrations while the conversion of ionic bromide to benzylic bromides is strongly influenced by the type of solvent and the presence of nucleophilic ligands and metal co-catalysts. The observed effects are best explained in terms of a chain carrier comprising both cobalt acetate and bromide. Oxidation of benzylic bromides under the reaction conditions results in the formation of benzal bromides, benzaldehydes, benzoic acid and molecular bromine. An electron transfer process is proposed to explain the oxidation of benzylic bromides.