Aromatic Monocarboxylic Acids Research Articles

Methodology for the determining aromatic monocarboxylic acids as products of phenylalanine and tyrosine metabolism: modern achievements and trends

A review on the quantitative determination of aromatic monocarboxylic acids (AMCAs), intermediates in the metabolism of the proteinogenic amino acids phenylalanine and tyrosine, in body fluids is presented. The importance of these compounds as potential diagnostic low-molecular-weight biomarkers of some human diseases is described. The main methodical features of current practical solutions in the field of highly sensitive screening of AMCAs in body fluids using chromatography-mass spectrometry and other methods actively used in clinical laboratory analysis are considered. Special attention is paid to the prospects of developing portable tools of therapeutic monitoring of the compounds of interest in biological fluids. <br> Bibliography includes 108 references.

Structural Variety of Niobium(V) Polyoxo Clusters Obtained from the Reaction with Aromatic Monocarboxylic Acids: Isolation of {Nb2 O}, {Nb4 O4 } and {Nb8 O12 } Cores.

The reactivity of aryl monocarboxylic acids (benzoic, 1- or 2-naphtoic, 4'-methylbiphenyl-4-carboxylic, and anthracene-9-carboxylic acids) as complexing agents for the ethoxide niobium(V) (Nb(OEt)5 precursor has been investigated. A total of eight coordination complexes were isolated with distinct niobium(V) nuclearities as well as carboxylate complexation states. The use of benzoic acid gives a tetranuclear core Nb4 (μ2 -O)4 (L)4 (OEt)8 ] (L=benzoate (1)) with four Nb-(μ2 -O)-Nb linkages in a square plane configuration. A similar tetramer, 7, was obtained with 2-naphtoic acid by using a 55 % humid atmosphere synthetic route. Two types of dinuclear brick were identified with one central Nb-(μ2 -O)-Nb linkage; they differ in their complexation state, with one bridging carboxylate ([Nb2 (μ2 -O)(μ2 -OEt)(L)(OEt)6 ], with L=1-naphtoate (3) or anthracene-9-carboxylate (5)) or two bridging carboxylate groups ([Nb2 (μ2 -O)(L)2 (OEt)6 ], with L=4'-methylbiphenyl-4-carboxylic (4) or anthracene-9-carboxylate (6)). An octanuclear moiety [Nb8 (μ2 -O)12 (L)8 (η1 -L)4-x (OEt)4+x ] (with L=2-naphtoate, x=0 or 2; 8) was obtained by using a solvothermal route in acetonitrile; it has a cubic configuration with niobium centers at each node, linked by 12 μ2 -O groups. The formation of the niobium oxo clusters was characterized by infrared and liquid 1 H NMR spectroscopy in order to analyze the esterification reaction, which induces the release of water molecules that further react through oxolation with niobium atoms, in different {Nb2 O}, {Nb4 O4 } and {Nb8 O12 } nuclearities.

Polar Aromatic Compounds in Soot from Premixed Flames of Kerosene, Synthetic Paraffinic Kerosene, and Kerosene–Synthetic Biofuels

Polar Aromatic Compounds (PAC) adsorbed on soot produced in laboratory premixed flames of fossil kerosene (Jet A-1), Synthetic Paraffinic Kerosene (SPK), and Jet A-1 - synthetic biofuels (2,5-dimethylfuran, methyloctanoate, diethylcarbonate and 1-butanol) were characterized for the first time in the aim of shedding light on the combustion mechanisms and evaluating the environmental impact of these synthetic biofuels. The following families of compounds were fractioned from the soot extracts and further their relative abundances estimated: (a) oxa-AHs (xanthenes, benzoxanthene, alcoxy-AHs, furan…); (b) aldehydes-AHs, (c) ketones-AHs; (d) quinones-AHs; (e) aromatic monocarboxylic acids; (f) aromatic hydroxy-acids; (g) aromatic dicarboxylic acids; (h) nitrated-AHs (including amines, acridines, cinnoline derivatives, carbazoles…); (i) nitro-AHs. The results obtained point out that overall, soot from Jet A-1 - biofuels premixed flames are richer in PAC than soot from pure Jet A-1 and SPK. Out of the fuels studied, Jet A-1 - 1-butanol produces the highest concentrations of nitro-AHs (namely nitro-benzaldehydes), of aldehydes-AH and hydroxy-AHs (including two isomers of hydroxy-benzaldehyde); whereas Jet A-1 - diethylcarbonate produces the highest concentrations of quinone-AHs (especially phenanthrene-quinones) and large concentrations of nitrated-AHs. On the other hand, soot from Jet A-1 - methyloctanoate is the richest one in mono aromatic and dicarboxylic acids, aromatic hydroxyacids, nitrated-AHs, and esters. Combustion of the Jet A-1 - 2,5-dimethylfuran mixture emits the highest concentrations of ketone-AHs, and oxa-AHs (namely, furan derivatives). We should remark that although the soot samples were obtained from pre-mixed flames, the lab conditions being far from the industrial conditions, particularly in terms of pressure; the chemistry going on should not be so different that our findings could not be extrapolated to industrial conditions.

Screening and characterization of a novel reversible 4-hydroxyisophthalic acid decarboxylase from Cystobasidium slooffiae HTK3.

Owing to carboxylation activity, reversible decarboxylases can use CO2 as a C1-building block to produce useful carboxylic acids. Although many reversible decarboxylases can synthesize aromatic monocarboxylic acids, only a few reversible decarboxylases have been reported to date that catalyze the synthesis of aromatic dicarboxylic acids. In the present study, a reversible 4-hydroxyisophthalic acid decarboxylase was identified in Cystobasidium slooffiae HTK3. Furthermore, recombinant 4-hydroxyisophthalic acid decarboxylase was prepared, characterized, and used for 4-hydroxyisophthalic acid production from 4-hydroxybenzoic acid.

Micellar and sub-micellar liquid chromatography of terephthalic acid contaminants using a C18 column coated with Tween 20.

The tremendous amounts of terephthalic acid (TPA) produced globally require consistent monitoring of its contaminants during the different stages of production for quality control purposes. In this paper, a simple, robust and green liquid chromatography method has been developed using an isocratic 100% aqueous mobile phase at pH 2 (dilute sulfuric acid) to separate TPA contaminants (mono-, di-, and tri-carboxylic aromatic acids) on a C18 stationary phase coated with Tween 20 (polyoxyethylene(20)sorbitan monolaurate). After optimization of all chromatographic conditions, near baseline separation of the nine carboxylic acids under investigation was achieved with a 2.5 mL/min flow rate on a 5 micron C18 silica column (100 x 4.6 mm) in under 20 min. The modified stationary phase showed an excellent capability to separate structural isomers in a reasonable time, markedly better that the bare C18 stationary phase. Plots of ln retention factor versus 1/temperature showed the expected linear relationship for the di- and tri-carboxylic aromatic acids (single retention mechanism likely) but a quadratic fit for the mono-carboxylic aromatic acids (dual retention mechanism likely). Due to the stability of the surfactant modified stationary phase, future potential mass spectrometry compatibility was shown through the alternative use of trifluoroacetic acid in the 100% H2O (no Tween) mobile phase but still with UV detection. The developed method with 0.001% (vol/vol) Tween in the mobile phase was successfully used to analyze two different types of TPA industrial samples for all nine components plus revealing some other impurity peaks. The lowest limit of detection was 0.010 nmoles for o-phthalic acid and p-toluic acid (PTA), while the highest was 0.065 nmoles for 4-carboxybenzaldehyde (CBA). The concentrations of these important contaminants, PTA and CBA, in the mother liquor sample were 3348mg/L and 1806mg/L, respectively, while their respective concentrations in the purified TPA powder were 135mg/kg and 17.7mg/kg.

Involvement of H+-gradient dependent transporter in PGE2 release from A549 cells

The purpose of this study was to identify the transporter involved in the release of prostaglandin E2 (PGE2). In the present study, transport assays were conducted using membrane vesicles prepared from human lung adenocarcinoma A549 cells, thus enabling identification of the novel exporter present in A549 cells. PGE2 transport into A549 vesicles was higher in the presence of a proton (H+)-gradient, thus suggesting the involvement of PGE2H+ symporter in PGE2 transport. Results from our experiments showed enhanced PGE2 release in A549 cells in the presence of H+-gradient ([H+]extracellular < [H+]intracellular). Moreover, in vesicular transport assays, H+-gradient-dependent transport of PGE2 did not show saturation up to 500 μM PGE2, and 10 mM aromatic monocarboxylic acids (acetylsalicylic acid, salicylic acid, and p-nitrobenzoic acid) significantly inhibited PGE2 transport by 62–70%. These results suggest, the involvement of monocarboxylate transporters in the H+-gradient-dependent PGE2 export.

Synthesis of Amphiphilic Conjugates Based on Silicon-Containing β-Cyclodextrin and Pharmacologically Important Acids

Amphiphilic conjugates were obtained containing fragments of pharmacologically important monocarboxylic aromatic acids, which are of interest for biomedical research, have been obtained basing on 6-O-tert-butyldimethylsilyl β-cyclodextrin derivative.

A one year study of functionalised medium-chain carboxylic acids in atmospheric particles at a rural site in Germany revealing seasonal trends and possible sources

This study presents a yearlong data set of 28 medium-chain functionalised carboxylic acids (C5 to C10) in atmospheric aerosol particles (PM10) from a German rural measurement station, which is analysed to obtain seasonal trends and evidences for possible sources of these rarely studied compounds. The analysed carboxylic acids were divided into four main groups: (I) functionalised aliphatic monocarboxylic acids, (II) functionalised aromatic monocarboxylic acids, (III) non-functionalised and functionalised aliphatic dicarboxylic acids, and (IV) aromatic dicarboxylic acids. A concentration maximum in summer was observed for aliphatic carboxylic acids, indicating mainly photochemical formation processes. For example, the highest mean summer concentrations were observed for 4-oxopentanoic acid (4.1 ng m−3) in group I and for adipic acid (10.3 ng m−3) in group III. In contrast, a concentration maximum in winter occurred for aromatic carboxylic acids, hinting at anthropogenic sources like residential heating. The highest mean winter concentrations were observed for 4-hydroxybenzoic acid (2.4 ng m−3) in group II and for phthalic acid (5.8 ng m−3) in group IV. For the annual mean concentrations, highest values were found for adipic acid and 4-oxopimelic acids with 7.8 ng m−3 and 6.1 ng m−3, respectively. The concentrations of oxodicarboxylic acids exceeded those of their corresponding unsubstituted form. Accordingly, straight-chain dicarboxylic acids might act as precursor compounds for their respective oxygenated forms. Similarly, unsubstituted monocarboxylic acids are possible precursors for functionalised aliphatic monocarboxylic acids. The present study contributes to the speciation of organic content on a molecular level of atmospheric particles, as well as giving hints for possible sources for these carboxylic acids.

Methods for the Synthesis of Polyethereketone

The data on the methods for the preparation of polyetherketones by electrophilic and nucleophilic methods are considered and generalized. It is shown that polyetherketones by electrophilic substitution are carried out as homopolycondensation aromatic monocarboxylic acids and their halides and polycondensation of polynuclear aromatic hydrocarbons with aromatic dicarboxylic acids or their halides, and phosgene in organic solvents (1,2-dichloroethane, methylene chloride, nitrobenzene and etc.) in the presence of Ziegler-Natt catalysts. However, this process has not found an industrial application in view of such disadvantages as low yield of the desired product, the formation of a polymer with low molecular weight, synthesis time (15-40 hours), the use of large amounts of catalyst, the complexity of polymer purification of it.

Direct esterification of the hydroxyl groups of β-cyclodextrin with some aromatic monocarboxylic acids

A possibility of the direct monoesterification of β-cyclodextrin with benzoic, p-aminobenzoic, 2-(4-isobutylphenyl)propionic, nicotinic, and isonicotinic acids was shown. Regioselectivity of substitution on the primary hydroxyl groups was confirmed by the means of 1H and 13C NMR spectroscopy.

Esterification of 2-hydroxypropyl β-cyclodextrin derivative with some aromatic monocarboxylic acids

Direct esterification of primary cyclodextrin hydroxy groups in 2-hydroxypropyl derivative of β-cyclodextrin with benzoic, 4-aminobenzoic, 2-(4-isobutylphenyl)propionic, nicotinic, and isonicotinic acids has been accomplished. The degree and regioselectivity of the substitution have been determined by 1H and 13C NMR spectroscopy.

Nanoscaled inclusion complexes of β-cyclodextrin with binuclear compounds based on diols containing fragments of selected aromatic monocarboxylic acids

Stable nanoscaled mono- and dimeric inclusion complexes of β-cyclodextrin with hosts based on symmetric diols of various length containing fragments of benzoic, nicotinic, or isonicotinic acid were synthesized.

Amphiphilic α-cyclodextrin derivatives containing residues of pharmacologically important acids

New representatives of amphiphilic α-cyclodextrin derivatives containing residues of pharmacologically important acids both at the primary and secondary hydroxyl groups were synthesized using acyl chlorides of palmitic acid and a series of aromatic monocarboxylic acids. The acyl chloride groups were assigned to the positions C(2), C(3), or C(6) of the carbohydrate fragments of α-cyclodextrin by 13C NMR spectroscopy.

Inclusion compound of β-cyclodextrin with binuclear guests containing residues of some pharmocologically important aromatic monocarboxylic acids

Stable monomeric and dimeric inclusion compounds of β-cyclodextrin with binuclear guests containing the residues of some pharmacologically important aromatic monocarboxylic acids were obtained.

Inclusion Complexes of ß-Cyclodextrin and Its Silyl Derivative with Some Pharmacologically Important Aromatic Monocarboxylic Acids

Stable host-guest complexes of a-cyclodextrin and its silyl derivative with some aromatic monocarboxylic acids of pharmacological interest were prepared. The structure of the a-cyclodextrin complex with nicotinic acid was studied by X-ray diffraction.

Synthesis of 2-oxazolines via boron esters of N-(2-hydroxyethyl) amides

A new, convenient, one-pot process is presented for the synthesis of 2-oxazolines in high yields (75–94%) via boron esters of N-(2-hydroxyethyl) amides. The procedure involves thermolysis of the boron esters at 240–260 °C, in the presence of solid CaO as an acid scavenger and allows the preparation of oxazolines from hydroxyethyl amides of aliphatic and aromatic monocarboxylic acids.

Synthesis and characterisation of main‐chain hydrogen‐bonded supramolecular liquid crystalline complexes formed by azo‐containing compounds

A series of azopyridine‐containing hydrogen bonding acceptors (4a–c) with flexible spacers of oligo(methylene) were synthesised. Hydrogen‐bonded polymeric complexes 4/5 and trimeric complexes 4/62 , where 5 and 6 are aromatic dicarboxylic acids and monocarboxylic acids, respectively, were prepared and their liquid crystallinity was examined using differential scanning calorimetry and polarising optical microscopy. The study showed that most of the complexes displayed reversible thermotropic nematic phase. The isotropic to nematic phase transition temperatures of polymeric complexes 4/5 and trimeric complexes 4/62 in general decreased with the increase in length of spacers and terminal groups in the corresponding proton acceptors 4 and the proton donors 5 and 6, respectively. Hydrogen bonding interactions in complexes 4/5 and 4/62 were studied by X‐ray photoelectron spectroscopy and Fourier transform infrared spectroscopy.

Synthesis of Monocarboxylic Aromatic Acids by Reaction Between Aromatic Nitriles and Phthalic Acid.

Synthesis of Monocarboxylic Aromatic Acids by Reaction Between Aromatic Nitriles and Phthalic Acid.

Lonza 2001: oxidation technologies

Mixture of some aromatic monocarboxylic acids (benzoic, salicyclic and p-hydroxybenzoic), dicarboxylic acids (phthalic, isophthalic and terephthalic) and tri-carboxylic acids (trimellitic and trimesic) were separated by ion-exchange chromatography on Dowex 50W using the ion-exclusion technique.The effect of cross-linking of the resin on the efficiency of the separation and also on the volume distribution coefficients of the acids was examined. It was found that the most efficient separation can be achieved by using Dowex 50W-X2, 200–400 mesh. The values found for the volume distribution coefficients of the acids decrease with increasing degree of cross-linking in most instances.The ion-exclusion method was applied to the determination of benzoic acid as a preservative in mustard. The advantage of the method is that an aqueous extract of mustard can be analyzed directly, without the need for an additional work-up, in a relatively short time (65 min) with an accuracy of ± 6.5%.

Structural study of the Moroccan Timahdit (Y-layer) oil shale kerogen using chemical degradations

This paper deals with the structural characterization of the Moroccan Timahdit (Y-layer) oil shale kerogen. For this purpose, the kerogen concentrate was submitted to stepwise hydrolysis under phase transfer catalysis conditions. The results show that aliphatic and aromatic dicarboxylic acids are involved in the cross-linking of the kerogen matrix, acting as bridges, while aliphatic and aromatic monocarboxylic acids, and alcohols represent monosubstituents of the matrix. Aliphatic mono- and dicarboxylic acids are produced on ruthenium tetroxide oxidation of the kerogen. These acids arise from a variety of reactions including cleavage of ester linkages. 17α(H),21β(H)- and 17β(H),21α(H)-hopanoic acids, probably bound to the kerogen by ether groups, were identified in the oxidation products.