Mixed Carboxylic Acid Research Articles

Catalytic Upgrading of a Mixed Hydroxy Acid Feedstock Derived from Kraft Black Liquor.

Lignocellulosic feedstocks are widely studied for sustainable liquid fuel and chemical production. The pulp and paper industry generates large amounts of kraft black liquor (BL) from which a high volume of hydroxy acids (HAs) can be separated for further catalytic processing. Here, we explore the catalytic upgrading of HAs, including the conversion of (1) a model HA, gluconic acid; (2) a model mixture of HAs, and (3) a real mixture of HAs derived from kraft BL on M/Nb2O5 (M = Pd, Pt, Rh, and Ru). The hydrodeoxygenation of model gluconic acid reveals that "volatile" carboxylic acids (mainly C2 and C3), levulinic acid, and cyclic esters are significant products over all the catalysts, with Pd/Nb2O5 showing superior activity and selectivity toward valuable intermediates. The model mixture of HAs shows a wide range of reactivity over the supported metal catalyst, with the product selectivity strongly correlating to reaction temperature. Utilizing a 0.25% Pd/Nb2O5 catalyst, a real mixture of HAs derived from kraft BL is successfully dehydroxylated to produce a mixture rich in C3-C8 carboxylic acids that may be amenable for further upgrading, e.g., catalytically to ketones with high carbon chain lengths. Despite the feedstock complexity, we selectively cleaved the C-OH bonds of HAs, while successfully preserving most of the -COOH groups and minimizing C-C and C=O bond scission reactions under the operating conditions tested. The BL-derived HA stream is thus proposed to be a suitable platform for producing mixed carboxylic acid products from an overoxygenated byproduct feed.

Techno Economic Analysis of the Modified MixAlco Process

The MixAlco process is a patented biomass conversion technology used to produce valuable chemicals. The basis of this design relies on the use of fermentation, where acidophiles utilize their own enzymatic pathways to convert a variety of biomass, such as organic wastes, into carboxylic acid salts. Unlike previous MixAlco designs in which carboxylate salts are processed further into hydrocarbon fuels, this proposed design simulates the optimization and commercialization of mixed carboxylic acid salts as the final product. Sensitivity analyses identified four critical input factors of the base case process—biomass feed rate, selling price, distribution cost, and biomass composition. Increasing the biomass feed rate or population size has the most pronounced effect on process economics. Overall, the sensitivity analyses of all four critical input factors support that the new design is flexible in its ability to support populations of varying sizes, as well as different biomass feed rates and compositions.

Harnessing chemical energy for the activation and joining of prebiotic building blocks.

Life is an out-of-equilibrium system sustained by a continuous supply of energy. In extant biology, the generation of the primary energy currency, adenosine 5'-triphosphate and its use in the synthesis of biomolecules require enzymes. Before their emergence, alternative energy sources, perhaps assisted by simple catalysts, must have mediated the activation of carboxylates and phosphates for condensation reactions. Here, we show that the chemical energy inherent to isonitriles can be harnessed to activate nucleoside phosphates and carboxylic acids through catalysis by acid and 4,5-dicyanoimidazole under mild aqueous conditions. Simultaneous activation of carboxylates and phosphates provides multiple pathways for the generation of reactive intermediates, including mixed carboxylic acid-phosphoric acid anhydrides, for the synthesis of peptidyl-RNAs, peptides, RNA oligomers and primordial phospholipids. Our results indicate that unified prebiotic activation chemistry could have enabled the joining of building blocks in aqueous solution from a common pool and enabled the progression of a system towards higher complexity, foreshadowing today's encapsulated peptide-nucleic acid system.

Rapid Destruction of Two Types of Chemical Warfare Agent Simulants by Hybrid Polyoxomolybdates Modified by Carboxylic Acid Ligands

Four chain-like hybrid compounds based on mixed carboxylic acid ligands-modified polyoxomolybdates, K2H[(H2O)4M][AsMo6O21(Ala)(PHBA)2]·nH2O 1–4 (M = Co, Ni, Zn, Mn; Ala = alanine; PHBA = p-hydroxybenzonic acid), were prepared and characterized by elemental analysis, IR spectroscopy, solid diffuse reflective spectroscopy, TG analysis, powder X-ray diffraction, and single-crystal X-ray diffraction. Four isostructural compounds 1–4 not only represent the extended architectures constructed from two different organic ligands-modified polyoxometalates but also can rapidly catalyze the degradation of two chemical warfare agent simulants, 2-chloroethyl ethyl sulfide (CEES) and diethyl cyanophosphonate (DECP), at room temperature. The catalytic results were analyzed and confirmed by GC-FID, GC-MS, and 1HNMR techniques. Within 5 min, CEES was high-selectively oxidized to the corresponding nontoxic 2-chloroethyl ethyl sulfoxide (CEESO) using heterogeneous catalyst 1 with the oxidant H2O2 (conversion % = 98.5%, selec...

A novel europium coordination polymer based on mixed carboxylic acid ligands: Synthesis, structure and luminescence

A novel europium complex, formulated as {[Eu4(H3Pimda)4 (Himba)2·4H2O]·4H2O}n (1) (H3Pimda=2-propyl-1H-imidazole-4,5-dicarboxy acid, and Himba=4-(1H-imidazole-1-ly) benzoic acid), has been obtained by the hydrothermal reaction. Single crystal X-ray diffraction analysis shows that complex 1 exhibits one-dimensional (1-D) ribbon-double chain composed of tetranuclear europium clusters, and these chains are further linked by Himba ligands into the 2-D corrugated layer arrays. Complex 1 exhibits efficiently sensitized red luminescence in visible region in N,N-dimethyl formamide (DMF) based on characterization emission of europium(III) ion. When Cd(NO3)2 is dropped in the DMF suspension of 1, the luminescence intensity increases linearly, rapidly, which indicates it may be employed as a fluorescent ratiometric probe for detection pollutant Cd(II) anion. In addition, complex 1 is characterized by elemental analysis, IR spectra, thermogravimetric (TG) analysis and PXRD measurement.

Binary self-assembled monolayers modified Au nanoparticles as carriers in biological applications.

Gold nanoparticles (AuNPs) are good nonviral carriers because of their ease of synthesis and conjugation in biochemistry, and self-assembled monolayers (SAMs) provide a tunable system to change their interfacial properties. Using homogeneously mixed carboxylic acid and amine functional groups, a series of surface potentials and isoelectric points (IEPs) could be obtained and allow systematic study of the effect of surface potential. In this work, the result of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay revealed that binary-SAM modified AuNPs have high biocompatibility with HEK293T cells. The amount of AuNPs ingested by the cells was found to increase with increasing surface potential and the difference was also confirmed with a scanning transmission electron microscope. The ability of binary-SAM modified AuNPs as carriers was examined, and the plasmid deoxyribose nucleic acid (DNA)-containing eGFP reporter gene was used as the model cargo. Fluorescence imaging revealed that the transfection efficiency generally increased with increasing surface potential. More importantly, when the IEP of the AuNPs was higher than that of the environment of the endosome but lower than that of the cytoplasm, the plasmid DNA can be protected better and released more easily during the endocytosis process hence higher efficiency is obtained with 60% NH2 and 40% COOH in the binary-SAM.

Assembling Mixed Carboxylic Acid Molecules on Hierarchical Structured Aluminum Substrates for the Fabrication of Superoleophobic Surfaces with Controlled Oil Adhesion

AbstractControlling oil adhesion on the superoleophobic surfaces is very important in both fundamental research and practical applications. Herein, we report a new method through modification of mixed carboxylic acid (CH3(CH2)6COOH and CF3(CF2)6COOH) molecules on hierarchical structured aluminum substrates toward the fabrication of superoleophobic surfaces with tunable adhesion. The oil adhesion can be controlled by changing the concentration of CF3(CF2)6COOH (xF) in the modified solution. Detailed research indicates that the tunable effect is ascribed to the combined effect of the surface chemistry variation and the hierarchical structures on the substrates. Furthermore, we also demonstrate an application of our surfaces in a droplet‐based microreactor. The results reported here can not only provide a new idea for fabrication of superoleophobic surfaces with tunable adhesion but can also potentially be used in many applications, such as microfluidic devices and chemical microreactors.

Thermal analysis of silver nanoparticles for flexible printed antenna fabrication

In this study, the temperature assisted decomposition/desorption behavior of short-chain single and mixed carboxylic acid encapsulants from the core of silver nanoparticles was investigated using thermogravimetric analysis and differential scanning calorimetry, and these particles were used to fabricate a flexible printed antenna. The decomposition temperatures of the single encapsulant particles increased with increasing chain length of encapsulants, whereas the decomposition temperatures for mixed encapsulant particles are close to the average of the corresponding decomposition temperatures of single encapsulant nanoparticles. These experimentally identified decomposition temperatures were utilized for sintering the printed antenna on a flexible substrate. The printed antenna showed a significantly low return loss of 22 dB. The antenna performance and radiation pattern are similar to a reference prototype antenna made of copper.

Tailoring the surface potential of gold nanoparticles with self-assembled monolayers with mixed functional groups

Self-assembled monolayer (SAM)-modified gold nanoparticles can be used to immobilize and transport molecules including DNA and proteins. However, these molecules are usually covalently bound to the surface and chemical reactions are required to cleave and release them. Therefore, immobilizing molecules using electrostatic interactions might be beneficial. In this work, Au nanoparticles modified by SAMs with mixed carboxylic acid and amine functional groups are presented. The surface potential and the iso-electric point (IEP) of the nanoparticles can be tailored by the ratio of these functional groups and arbitrary IEPs between 3.2 and 7.3 can be achieved. As a result, based on electrostatic interactions, molecules could be triggered to adsorb/desorb by changing the environmental pH around this tunable IEP. These engineered nanoparticles were synthesized in a single-phase system based on the reduction of HAuCl 4 by NaBH 4 in ethanol with a mixture of 16-mercaptohexadecanoic acid and 8-amino-1-octanethiol that forms the SAM on the synthesized nanoparticles. Transmission electron microscopy, X-ray photoelectron spectroscopy, and electrophoresis light scattering revealed the particle size, ratio of the functional groups, and zeta-potential of the particles as a function of pH, respectively.

X-ray crystal structures and isostructurality calculation of calix[4]arenes with lower rim propyl and carboxylic acid or mixed carboxylic acid and ester substituents involving solvent complexes with methanol and ethanol

X-ray crystal structures of two calix[4]arenes are reported. They feature aside from two distal n-propyl units, two ethyl acetate or mixed ethyl acetate and acetic acid groups as the characteristic substituents of the lower rim hydroxylic hydrogens. The structures are compared by making use of isostructurality calculations. In case of the semi-ester, solvates with methanol and ethanol as the guest solvents are involved. The carboxy function of the semi-ester does not form a dimer but an intramolecular hydrogen bond to a propoxy group. The solvates can be described as isostructural in spite of the different solvent molecules.

Denaturation of Cytochrome c and Its Peroxidase Activity When Immobilized on SAM Films

This work uses cytochrome c, an electron carrier in the respiratory chain, as a model to probe how surface adsorption affects the folding of a protein. The electrochemical activities of the protein horse heart cytochrome c is studied under conditions where it is covalently attached onto a mixed carboxylic acid and hydroxyl-terminated SAM, which covers a Au electrode's surface. Changing the pH of the electrochemical buffer solution changes the conformation of the cytochrome c and causes a change of the peak currents in cyclic voltammetry and a shift of the peak potential. In addition, the unfolded cytochrome c displays peroxidase activity; the apparent Michaelis−Menten constant Km for cytochrome c at these surfaces has been determined to be 7.9 mM at pH 3 and 144.3 mM at pH 7.

Synthesis and properties of nickel borate acylate as a new rubber-steel cord adhesion promoter

The synthetic method of nickel borate acylate (NBA), a kind of rubber-steel cord adhesion promoter (AP), through nickel carbonate, borate and mixed carboxylic acid was studied. The preparation of nickel carbonate could be performed through reaction of nickel sulfate with sodium carbonate in aqueous solution, in which fractional conversion of nickel was more than 99.9%. The mixed nickel carboxylate was prepared by the reaction of nickel carbonate with isooctanoic acid and acetic acid, under strong stirring for 2 h, the mole ratio of these chemicals were 1:1:1.1 respectively, and water should be removed completely by adding of inert organic solvent after reaction was finished so as to avoid hydrolysis of tributyl borate in the second reaction. NBA was synthesized by reaction of mixed nickel carboxylate with tributyl borate under strong stirring at 200–250 °C for 6 h. By detection and comparison with 680C product from Manobond Company of England, the NBA synthesized through isooctanoic acid and tributyl borate was very similar to product 680C in IR data, 300% fixed extension strength, tensile strength, hardness and cure curve, and was slightly lower than those of product 680C in tensile failure extensibility and hot air aging. The experimental results show that the prepared NBA can be used as rubber-steel cord AP.

Chelat‐stabilisierte 1,3‐Bis(acyloxy)‐1,3‐diethyldiboroxane aus Triethylboroxin und Carbonsäureanhydriden

Chelate‐Stabilized 1,3‐Bis(acyloxy)‐1,3‐diethyldiboroxanes from Triethylboroxin and Carboxylic Acid AnhydridesTriethylboroxin (A) reacts with carboxylic acid anhydrides (RCO)2O [R = Me: 1a; Et: 1b; tBu: 1d; Ph: 1e] with various rates to give high yields of the 3,7‐dialkyl‐1,5‐diethyl‐4,8,9‐trioxa‐2,6‐dioxonia‐1,5‐diboratabicyclo[3.3.1]nona‐2,6‐dienes OB(Et)OC(R)OB(Et)OC(R)O (2) [R = Me: 2a (X‐ray crystal structure analysis); Et: 2b; tBu: 2d; Ph: 2e], presumably via the unstable compounds OB(Et)OB(Et)OC(R)OB(Et)OC(R)O (3a,b, d, e). Compound 1c (R = CF3) reacts with A to form a mixture of 1,3‐diethyl‐1,3‐bis(trifluoroacetoxy)diboroxane OC(CF3)OB(Et)OB(Et)O(CF3)CO (2c′) and 2c (R = CF3) at room temperature. Whereas two compounds of the type 2 do not comproportionate, 1a–e spontaneously form the mixed substituted carboxylic acid anhydrides 1ab etc. on mixing at room temperature (GC, 13C NMR). ‐ From the 17O‐enriched A* and 1a–e the 17O‐enriched compounds 2a*‐e* with BO*B and YYBO*OCR groups are obtained. A* exchanges O atoms up to 200°C with succinic anhydride (1f) forming 1f* or with phthalic acid anhydride (1g) forming 1g* and 3g*. ‐ The mixed carboxylic acid anhydrides 1xy are cleaved, and the mixtures of 1 are separated with A to yield the uniform 3,7‐dialkyl‐substituted compounds 2.

Synthesis, characterization, and catalytic properties of polysiloxanes with pendant 4-(3-pyridinyl)butyl and 4-(1-oxypyridin-3-yl)butyl groups

New silane monomers with the pendant 4-(3-pyridine)butyl group have been synthesized by hydrosilation of 3-(3-butenyl)pyridine with Me n Si(OEt)3-n H (n=0, 1) using a platinum catalyst. Only β-addition products were observed. The products were characterized by elemental analysis, infrared,1H- and13C-NMR spectroscopy, and gas chromatography-mass spectrometry. Hydrolysis-polycondensation of the difunctional monomer with a basic catalyst, Me4NOH, gave a mixture of cyclic oligomers, principally cyclic tetramer, and linear homopolymer. Under similar reaction conditions, the trifunctional monomer gave crosslinked material which was soluble in common organic solvents. The linear homopolymer and crosslinked polymer were trimethylsilyl end-blocked with hexamethyldisilazane. The cyclic and end-blocked polymers were characterized by elemental analysis and spectroscopic methods. Molecular weights of the polymers were obtained by end-group analysis using1H-NMR spectral data, size exclusion chromatography, and direct insertion-probe mass spectrometry. The cyclic, linear, and crosslinked materials were N-oxidized withm-chloroperoxybenzoic acid and characterized by spectroscopic methods. The polymeric N-oxide derivatives were shown to be effective transacylation catalysts in the synthesis of mixed carboxylic acid anhydrides in immiscible solvents (H2O/CH2Cl2) under phase-transfer conditions. The implications of the results on the mechanism of catalysis are discussed.

Studies on the disproportionation of mixed anhydrides of N-alkoxycarbonylamino acids.

Mixed anhydrides from Z-valine and ethyl, isobutyl, isopropyl and isopropenyl chloroformate, and from N-tert-butoxycarbonyl- (Boc) and N-benzyloxycarbonyl- (Z) leucine and phenylalanine and Boc- and N-9-fluorenylmethoxycarbonyl-valine and ethyl chloroformate were purified and left in dichloromethane at 23 degrees C. The symmetrical anhydride (SyAn) generated after 24 h was determined by normal phase high-performance chromatography. No SyAn was produced from the anhydrides of Z- and Boc-valine; SyAn was produced from the other anhydrides. Anhydrides examined without isolation generally produced more SyAn than the pure compounds. More SyAn was generated in dimethylformamide and tetrahydrofuran than in dichloromethane, or in the presence of an excess of N-methylmorpholine or triethylamine. The anhydride from isobutyl chloroformate was much more stable than the anhydride from ethyl chloroformate. It is suggested that disproportionation of pure mixed carboxylic acid--carbonic acid anhydrides occurs by a bimolecular mechanism.

Crystal structures and photochemistry of α-cyclopentyl-4-carboxypropiophenone and α-cyclooctyl-4-carboxypropiophenone–acetic acid (1:1 mixed carboxylic acid dimer)

C 15 H 18 O 3 cristallise dans P1 avec affinement jusqu'a 0,076. C 18 H 24 O 3 •C 2 H 4 O 2 cristallise dans P1 avec affinement jusqu'a 0,044. Les propiophenones occupent les positions equatoriales sur les cycles alkyl avec les parametres moleculaires sont favorables a une reaction photochimique par abstraction d'hydrogene

Selenoesters in organic synthesis. 1. Conversion of mixed carboxylic acid esters to selenoesters

The rules governing the reaction of mixed carboxylic acid esters with dimethylaluminum methyl selenide have been investigated; it was found that the nature of the solvent and the structure of the precursor ester both exert significant effects on the selectivity of selenoester formation.

Partially modified retro‐inverso peptides

Several synthetic routes are reported to prepare the hetero diprotected 1,1-diaminoalkanes from N-acylated amino acids or peptides for incorporation into partially modified retro-inverso peptides. The Curtius rearrangement was carried out on the N-protected aminoacyl azides obtained from the N-protected aminoacyl hydrazide by nitrosyl chloride or by sodium azide reaction with an appropriate mixed carboxylic carbonic acid anhydride. The resulting isocyanate was allowed to react with alcohol to give a urethane-type protecting group or, via a "one-pot" approach, directly with a carboxyl carrying component to yield the modified (reversed) peptide bond. The carboxyl component can be either an N-acylated amino acid or a malonic acid. The more standard route involves selective deprotection of the 1,1-diaminoalkane residue followed immediately by coupling with a carboxyl component to yield the same modified peptide derivative.

Oxidation of thiolesters : Some aspects of the chemistry of s-acylthiol s-oxides and related compounds

In the ozone oxidation of thiolesters in 1,2-dichloroethane at room temperature, S-acylthiol S-oxides 3 are proposed as intermediates. The isolation of carboxylic acid anhydrides and dialkyl disulphides as the actual reaction products can be explained as resulting from the decomposition of the unstable. S-acyl S-acyloxysul-phonium salt 4 arising probably from the reaction of the intermediate S-acylthiol S-oxides with another mole of thiolester. However, in the case of hindered thiolesters, the S-acylthiol S-oxides formed rearrange, possibly via an S→ O acyl shift, to the corresponding acyl sulphenates 12 which on further oxidation lead to the mixed carboxylic acid sulphonic acid anhydrides 13.

Acylation des enolates lithiens d'esters ou de cetones au moyen d'anhydrides mixtes carboxyliques et carboniques: preparation de β-cetoesters et de β-dicetones

Lithium esters and ketoenolyllithium compounds react with mixed carboxylic and carbonic acid anhydrides to give, respectively, β-ketoesters and β-diketones in satisfactory yields.