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The present paper describes the fabrication of a new polyvinylchloride (PVC) membrane electrode for the determination of Nd(III) ion based on 4-hydroxypyrrolidine-2-carboxylic acid (LHP) as an active material along with sodium tetraphenyl borate (NaTPB) as an anionic additive and acetophenone (AP) as solvent mediator. The optimum composition (%, w/w) of the best performing membrane contained 66 AP, 30 PVC, 2 NaTPB and 3 LHP. The basic analytical parameters of this electrode such as slope characteristics, detection limit, response time, selectivity and pH effect were assessed. The electrode displayed a Nernstian response in terms of slope (20.5 [+ or -] 0.4 mV per decade) and response time (~8 [+ or -] 1 s) over a wide neodymium ion concentration range of [10.sup.-6] to [10.sup.-2] M with a detection limit of 7.5 x [10.sup.-7] M. The potentiometric response of the electrode was constant in the pH range of 3.2-8.9. According to the selectivity coefficients determined by the matched potential method, the interference of many common alkaline, alkaline earth, transition, heavy metals and specially lanthanide ions in determination of Nd(III) ion was very low. The proposed electrode has been successfully used as an indicator electrode in the potentiometric titration of Nd(III) ion with EDTA and applied for determination of Nd(III) ion in mixtures of different ions. Keywords: neodymium, 4-hydroxypyrrolidine-2-carboxylic acid (LHP), PVC membrane, potentiometric, sensor, ion-selective electrode DOI: 10.1134/S1061934818010094, Due to the advantages of PVC membrane sensors based on ion carrier over the other analytical methods such as spectrophotometry, mass spectrometry, inductively coupled plasma atomic emission spectrometry, inductively coupled [...]

The paper describes the results of extraction of aromatic microbial metabolites (phenylcarboxylic acids) from model aqueous solutions using microextraction by packed sorbent (MEPS), followed by the determination of their silyl derivatives by gas chromatography/mass spectrometry. The selected conditions of adsorption-desorption, derivatization, and gas chromatography determination enable the detection of a number of compounds, which are proved and prospective disease markers. This detection could be performed at the level of their concentration in blood of healthy donors (0.5 [micro]mol [L.sup.-1]) and patients of intensive care units, having an initial stage of sepsis (2-3 [micro]mol [L.sup.-1]) or other serious diseases caused by significant microbial load and led to the development of multiple organ failure. The recoveries of phenylcarboxylic acids using nonpolar sorbent (C18) reached 20-65% for hydroxylated acids (phenyllactic, 4-hydroxybenzoic, 4-hydroxyphenylacetic, 4-hydroxyphenylpropanoic, homovanillic, and 4-hydroxyphenyllactic acids) and 100% for more nonpolar acids (benzoic, phenylpropanoic, and cinnamic acids). Keywords: microextraction by packed sorbent, gas chromatography/mass spectrometry, aromatic microbial metabolites, phenylcarboxylic acids, early diagnostics of sepsis, DOI: 10.1134/S1061934817140131 INTRODUCTION Metabolomic research in the diagnostics of various diseases is an actual and demanded trend. To implement this approach, new solutions in qualitative and quantitative chemical analysis are [...]

Monoalkyl esters of benzene-1,2-dicarboxylic (phthalic) acid have not been reliably characterized by analytical parameters for their chromatographic and chromatospectral identification. Mass spectra of a series of monoalkyl phthalates (R = [C.sub.1]-[C.sub.8]) are discussed; their gas chromatographic retention indices on the RTX-5 polydimethylsiloxane stationary phase (5% phenyl groups) are determined. A linear dependence of indices on the number of carbon atoms in n-alkyl fragments of molecules and a correlation between the indices of any monoalkyl phthalates and corresponding diesters were used for the control of the data obtained. Using the last correlation, we found that most part of index values of mono (2-ethylhexyl) phthalate given in literature is wrong and, therefore, the results of identification of this compound in various samples must be revised. It was found that simplest monoalkyl phthalates are unstable during gas chromatographic separation, which may result in distortions of their mass spectra. To compare with monoalkyl phthalates, a similar series of monoesters of (Z)-butenedioic (maleic) acid was characterized. Retention indices of monoalkyl phthalates in reversed phase HPLC were determined and discussed. Keywords: phthalic acid, maleic acid, monoalkyl esters, gas chromatographic retention indices, reversed phase HPLC, mass spectrometry, Present-day chromatographic and chromatospectral identification of organic compounds in complex mixtures implies a comparison of their mass spectra and chromatographic retention parameters (indices) with reference data. Algorithms of such comparison [...]

A simple, low-cost capillary electrophoresis--mass spectrometry (CE-MS) method is demonstrated for the simultaneous analysis of amino acids and small carboxylic acids (glycerate, lactate, fumarate, succinate, malate, tartrate, citrate, iso-citrate, cis-aconitate, and shikimate). All CE-MS experiments were performed using a single uncoated fused-silica capillary and with a single separation electrolyte, formic acid. For CE polarity, the CE inlet was set as the anode, and the MS side was set as the cathode. By using high-speed sheath gas flow, the apparent mobilities of all compounds were sped up; thus, the migration times of the carboxylic acids were reduced. In positive ion mode ESI-MS detection, small carboxylic acids were detected faintly as m/z = [[M + 18].sup.+] or [[M + 23].sup.+], after protonated molecule detection (m/z = [[M + 1].sup.+]) of the amino acids. In negative ion mode, all of these small carboxylic acids were detected clearly as deprotonated molecules (m/z = [[M - 1].sup.-]), after detection of the amino acids. By changing the polarity of the MS during CE separation, both amino acids and small carboxylic acids were detectable in a single electrophoresis analysis run. With this method, the diurnal metabolic changes of pineapple leaves were observed as reflecting Crassulacean acid metabolism. 10.1021/ac1019039

We have developed a new isotope labeling method, based on the use of isotope-coded p-dimethylaminophenacyl (DmPA) bromide as a reagent, combined with liquid chromatography--mass spectrometry (LC--MS) for high-performance metabolome analysis with a focus on profiling carboxylic acid-containing metabolites. Derivatization is simple, fast (1 h plus 30 min for quenching the reaction), and applicable to a wide range of carboxylic acids with a high yield and little or no side reaction products. This labeling method is demonstrated to be not only effective in introducing an isotope tag for accurate metabolite quantification but also improving the chromatographic retention of the metabolites in reversed-phase (RP) LC, enhancing ESI efficiency by 2-4 orders of magnitude, and facilitating the identification of metabolite peaks in LC--MS. In triplicate experiments of a 1:1 ratio of [sup.13]C-/[sup.12]C-DmPA labeled human urine, we were able to detect 2671, 2546, and 2820 ion pairs from metabolites containing one or more carboxylic acid groups. 10.1021/ac102146g

No barrier theory (NBT) provides both a qualitative way of thinking about what makes a reaction fast or slow and a quantitative way of calculating the rate constant (free energy of activation) corresponding to a particular mechanism. The origin and development of this idea are reviewed and examples of its use for qualitative understanding are presented before applying it to a set of decarboxylations. From the literature, a set of best values for rate constants for decarboxylation was picked. Detailed mechanistic models were developed for reactions leading to delocalized 'anions' or to localized anions. It was necessary to have [pK.sub.a] values for ionizaion of the carbon acids corresponding to all of these species and these were selected from the literature or estimated by linear free energy relations (or occasionally calculated from proton exchange data). Over the entire range of measured decarboxylation rate constants, a range of 1025 in rate constant, the calculated values were in good agreement with experiment, with two exceptions: malonate dianion, which has been reported but probably not measured, and glycine, where it is possible that a different mechanism is being followed, unfortunately, one which we do not yet know how to treat by NBT. NBT is both a qualitatively and quantitatively useful tool for understanding chemistry. Key words: decarboxylation, no barrier theory, reaction mechanism, intrinsic barrier. La theorie sans barriere fournit d'une part une facon qualitative de reflechir sur ce qui fait qu'une reaction est rapide ou lente et d'autre part une facon quantitative de calculer la constante de vitesse (energie libre d'activation) correspondant a un mecanisme particulier. On passe en revue l'origine et le developpement de cette idee et on presente des exemples de son utilisation dans la comprehension qualitative avant de l'appliquer a un ensemble de decarboxylations. On a tire de la litterature un ensemble des meilleures valeurs pour les constantes de vitesse de decarboxylation. Des modeles de mecanismes reactionnels detailles ont ete developpes pour des reactions conduisant a des anions delocalises ou localises. Il etait necessaire d'avoir les valeurs de [pK.sub.a] pour l'ionisation des acides carboniques correspondants a chacune des especes et celles-ci ont ete selectionnees a partir de la litterature ou elles ont ete evaluees par des relations d'energie lineaires ou elles ont ete occasionnellement calculees a partir de donnees d'echange de proton. Sur l'ensemble complet des constantes de vitesse de decarboxylation, une plage de constantes de vitesse relatives s'etalant de 1 a 1025, les valeurs calculees ont en bon accord avec les valeurs experimentales, a deux exceptions pres: le dianion de l'acide malonique a ete rapporte, mais qui n'a probablement pas ete mesure et la glycine pour laquelle il est possible qu'un mecanisme different soit implique, un mecanisme qu'on ne peut malheureusement pas encore traiter par la theorie sans barriere. La theorie sans barriere (TSB) est un outil qualitativement et quantitativement utile pour la comprehension de la chimie. Mots-cles : decarboxylation, theorie sans barriere, mecanisme reactionnel, barriere intrinseque. [Traduit par la Redaction] doi:10.1139/V09-164, Introduction Over the past ten years, we have been developing an approach to calculating rate constants for chemical reactions, which also provides a useful way to think about why a [...]

A mass spectrometric method has been developed for the identification of the carboxylic acid functional group in analytes evaporated and ionized by electrospray ionization (ESI). This method is based on gas-phase ion-molecule reactions of ammoniated ([[M + N[H.sup.4]].sup.+]) and sodiated ([[M+ Na].sup.+]) analyte molecules with trimethyl borate (TMB) in a modified linear quadrupole ion trap mass spectrometer. The diagnostic reaction involves addition of the deprotonated analyte to TMB followed by the elimination of methanol. A variety of analytes with different functionalities were examined, and this reaction was only observed for molecules containing the carboxylic acid functionality. The selectivity of the reaction is attributed to the acidic hydrogen present in the carboxylic acid group, which provides the proton necessary for the elimination of methanol. The diagnostic products are easily identified based on the m/z value of the product ion, which is 72 Th (thomson) greater than the m/z value of the charged analyte, and also by the characteristic isotope pattern of boron. The applicability of this method for pharmaceutical analysis was demonstrated for three nonsteroidal anti-inflammatory drugs: ibuprofen, naproxen, and ketoprofen.

The development of two new methods to synthesize 2-aminothiazolones from 2-(4-methoxybenzylthio)acetic acid are described. The method could find future application in the synthesis of enantiomerically enriched C5-disubstituted 2-aminothiazolones and 2-thiothiazolones from enantiomerically enriched carboxylic acids.

Several studies were conducted to understand the intrinsic conformational preferences of 1-amino-2-phenylcyclopentane-1-carboxylic acid ([C.sub.5]Phe), a constrained analogue of phenylalanine. The results suggest that the conformational space of the cis stereoisomer is more restricted than the trans derivative for both in the gas phase as well as solution phase.

Coacervates made up of alkanoic ([C.sub.8]-[C.sub.16]) and alkenoic ([C.sub.18]) acid reverse micelles were described for the first time, and their potential for the extraction of organic compounds prior to liquid chromatography was examined. The coacervation process occurred in miscible binary mixtures of water and a variety of protic and aprotic solvents. The phase behavior of alkyl carboxylic acids was found to be a function of both the Hildebrand solubility parameter, [delta], and the hydrogen-bonding capability of the solvent. The best solvents for analytical extractions were those featuring the lowest [delta] values. The phase behavior of alkyl carboxylic acid/water/tetrahydrofuran (THF) ternary systems as a function of component concentration, pH, ionic strength, and temperature was investigated. The efficiency and the time required for phase separation depended on the experimental procedure used (i.e., standing, centrifugation, stirring, and sonication). The formation of alkyl carboxylic acid reverse micelles in THF was proven using both hydrophilic fluorescent probes and scattered light measurements. The structure of the coacervates consisted of spherical droplets dispersed in a continuous phase. Phase volume ratios were a function of both alkyl carboxylic acid and THF concentration. The low volume obtained (e.g., 1.5 [micro]L per mg of decanoic) compared to that obtained by other coacervates (e.g., 5.1 [micro]L per mg of dodecane sulfonic acid and 11.3 [micro]L per mg of Triton X-114) greatly improved the concentration factors reached by coacervation-based extractions. Parameters affecting the extraction efficiency were assessed. Analytes in a wide range of polarity were efficiently extracted on the basis of the hydrophobic (e.g., PAHs) and hydrogen bond (e.g., chlorophenols, bisphenols, pesticides, phthalates, nonionic surfactants, dyes, and photographic developers) interactions that reverse micelles can establish. The coacervates were compatible with the chromatographic determination of analytes following UV or MS detection. They were successfully applied to the extraction of alkylphenol ethoxylates (octyl and nonyl) and alcohol ethoxylates ([C.sub.12]-[C.sub.16]) from influent and effluent wastewater and river water samples. Nonionic surfactants in the coacervate were directly separated and quantified by liquid chromatography--ion trap mass spectrometry. Concentration factors were around 160. The recovery of nonionics in the environmental water samples ranged from 90 to 104%.

Optimization of the kinetic resolution of 2-amino-4-phenyl-butane is achieved at 80 [degree]C by using CALB-catalyzed aminolysis of carboxylic acids and their ethyl esters. The optimized conditions are applied to the resolution of a series of aliphatic and benzylic amines.

The enzyme 2- hydroxychromene-2-carboxylix acid (HCCA) isomerase catalyzes the glutathione (GSH)-dependent interconversion ([K.sub.eq] =1.5) of HCCA and trans-a-hydroxybenzylidene pyruvic acid (tHBPA) in the naphthalene catabolic pathway of Pseudomonas putida. The results suggests that isomerization reaction involves a short-lived covalent adduct between the sulfur of GSH and C7 of the substrate.

A simple and rapid 'one-pot' methylation method to esterify sialic acids and construct a permanent charge was developed for N-linked glycan analysis, which combined complete nonspecific proteolytic digestion and methylation. A mixture of Asn-glycans prepared from Pronase E digestion of the glycoprotein was passed through a cation-exchange column to convert carboxylic acids to the [Na.sup.+] form before being methylated with methyl iodide. Derivatives could be easily purified with a hydrophilic affinity chromatography cartridge. Mass spectrometry analysis was performed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) and MALDI-TOF/TOF. The mass spectrometric data indicated that carboxylic acids were methylated in addition to the formation of a quaternary ammonium in the amino group of asparagine residues. Three model glycoproteins, including ribonuclease B, ovalbumin, and transferrin, were employed to demonstrate the merits of this technique. Results showed that the stabilization of sialic acid was achieved in addition to the formation of a permanent charge. Compared to the analysis of underivatized N-glycans, detection sensitivity improved ~10-fold. The new technique was further evaluated with glycan profiling of serum transferrin and proved to be a sensitive method for the characterizing protein glycosylation.

The modification of proteins by the cytotoxic, reactive aldehyde 4-hydroxynonenal (HNE) is known to alter protein function and impair cellular mechanisms. In order to identify susceptible amino acid sites of HNE modification within complex biological mixtures by microcapillary liquid chromatography and linear ion trap tandem mass spectrometry, we have developed a solid-phase capture and release strategy that utilizes reversible hydrazide chemistry to enrich HNE-modified peptides. To maximize the detection of fragment ions diagnostic of HNE modification, both neutral loss-dependent acquisition of MS/ MS/MS spectra and the pulsed Q dissociation operation mode were employed. When the solid-phase hydrazide enrichment strategy was applied to a yeast lysate treated with HNE, 125 distinct amino acid sites of HNE modification were mapped on 67 different proteins. The endogenous susceptibility of many of these proteins to HNE modification was demonstrated by analyzing HNE-treated yeast cell cultures with a complementary biotin hydrazide enrichment strategy. Further analysis revealed that the majority of amino acid sites susceptible to HNE modification were histidine residues, with most of these sites being flanked by basic amino acid residues, and predicted to be solvent exposed. These results demonstrate the effectiveness of this novel strategy as a general platform for proteome-scale identification of amino acid sites susceptible to HNE modification from within complex mixtures.

The solid-state NMR spectroscopy technique is employed to study and describe the coupling of functional hydrogen bonds in the models of the confactor pyridoxal-5'-phosphate (PLP) with carboxylic acids that mimic the confactor of various enzyme active sites. The analysis proves a shift in the proton to the Schiff based nitrogen, followed by an increase in the positive charge of the nitrogen atom, which can be avoided by introducing an aromatic substituent in the model.

The NMR titration methods, applicable to a mixture of isotopologues are employed to study various secondary deuterium isotope effects (IEs) on the acidity of several carboxylic acids and phenols. The results of the analysis clearly prove that though the delocalization for aromatic acids does not account for the constancy of IEs from the deuterium, the observed IEs are always consistent with the vibrational frequencies and electron densities.

The synthesis of chalcogenorhodamines by using dianions generated from 5-bromothiophene-2-carboxylic acid and 3-bromothiophene-2-carboxylic acid through metal-halogen exchange with tert-butyllithium (t-BuLi) are reported. The analysis has shown that the deprotonation is faster than metal-halogen exchange with the bromothiophene-2-carboxylic acids using t-BuLi.

Racemic 1-arylaaziridine-2-carbonitriles were catalyzed by the Rhodococcus erythropolis. It was found that 1-phenylaziridine-2carboxamide undergoes readily the Lewis acid catalyzed ring opening reaction with an azide.

The synthesis of a branched flexible linker that terminates in amino and carboxylic acid functional groups to facilitate incorporation of the linker into multimeric peptide ligand constructs by solid-phase synthesis is reported. In vitro biological evaluations showed that potency of binding to the human melanocortin 4 receptor was not diminished for linker-ligand combinations relative to the corresponding ligand alone.

Mononuclear iron(II)- and iron(III)-catecholato complexes with three members of a new 3,3-bis(1-alkylimidazol-2-yl)propionate ligand family are compounded as models of the active sites of the extradiol cleaving catechol dioxygenases. The iron(II)-catecholato complexes react with dioxygen in two steps, where in the first reaction the iron(II)-catecholate complexes rapidly convert to the corresponding iron(III) complexes, which subsequently, in second slow reaction, exhibit both oxidative cleavage and auto-oxidation of the substrate.

A mild and efficient surface activation protocol to convert polycarbonate (PC) substrates, e.g., plastic bases of compact disks, to biochip platforms for DNA probe immobilization and target detection is described. The preparation procedure (activation, patterning, and coupling) is simple and effective; the on-chip hybridization is sensitive and selective. Particularly, UV/ozone treatment of PC sheets produces a hydrophilic surface with a high density of reactive carboxylic acid groups [(4.8 [+ or -] 0.2) x [10.sup.-10] mol/[cm.sup.2]] in less than 10 min at ambient conditions, and no significant aging or physical damage to the substrate is observed. Covalent immobilization of DNA probes via both passive (reagent-less photopatterning and coupling in bulk solution phase) and flow-through (creation of microarrays with microfluidic channel plates) procedures has been demonstrated. Subsequent hybridization shows uniform and strong fluorescent signals for complementary target DNA and allows clear discrimination between fully complementary targets and strands with a single base-pair mismatch. The surface chemistry described herein will facilitate the development of disposable plastic biochips (not limited to DNA microarrays) and the fabrication of biomedical devices that are readable with conventional optical drives.

A research focuses on a mechanistic study of the mechanism involved in an effective asymmetric hydrogenation and reduction of [alpha],[beta]-unsaturated carboxylic acid, which is usually catalyzed by several Ruthenium complexes having axially chiral ligands. The results show that protonolysis is the major pathway for metal-carbon cleavage under neutral conditions, where as the hydrogenolysis of metal-carbon bond predominates under the basic conditions.

A simple, efficient and broadly applicable general method for the preparation of alkyl, unsaturated, (hetero)aryl, and N-protected [alpha]-amino ketones was developed by acylation of the corresponding N-acylbenzotriazoles with Grignard and heteroaryllithium reagents. The method used accessible acylating agents without any requirement of additional transition metal catalysts or organic ligands to obtain excellent yields of ketones.

A Friedlander condensation approach was used to prepare a series of 2-(pyrid-2'-yl)-1,8-naphthyridines containing a carboethoxy group appended at the 4- and 4'-positions. It was observed that the complexation of these ligands with Ru(II) and NaNCS led to the complexes [Ru[(L).sub.2][(NCS).sub.2]], and subsequent hydrolysis of the ester groups formed carboxylic acid dyes.

Polarography was used to obtain the concentrations of the dialdehydic (10%), monohydrated acyclic (5%), and cyclic hemiacetal form (85%) of orthophthalaldehyde (OPA). For 2,3-naphthalenedicarboxaldehyde (NDA) these values were estimated to be 15, 7, and 78%. Addition of water in unbuffered solutions followed first-order kinetics with rate constants 0.0018 [s.sup.-1] for OPA and 0.0012 [s.sup.-1] for NDA. Dehydration to form both the dialdehyde and the monohydrate is both acid- and base-catalyzed. Both dialdehydes yield on reaction with OH- ions geminal diol anion, which is electro-oxidized to a carboxylic acid. In the most frequently used pH range for the determination of amino acids, NDA can undergo reaction with OH ions, but OPA does not. In aqueous solutions, NDA is less strongly hydrated than OPA.

A study report shows significant stabilization of complexes of metal ions of a tetradentate ligand, 1,10-phenanthroline-2,9-dicarboxylic acid (PDA), which is derived by attachment of donor groups to the 2 and 9 positions of 1,10-phen and owes its high level of preorganizations to the rigidity of its 1,10-phen-based backbone. PDA is a member of an unrecognized class of ligands, which includes 1,10-phen itself, showing levels of preorganization higher than that of macrocycles, and promise of being useful in a wide variety of applications.

A structural extension based on the elongation of the bridging ligands by the replacement of iosH with longer 4-pyridyl-substituted carboxylic acid (PCA) was conducted for the expansion of a rectangular cavity (RC) defined by two isonicotinic acid (iosH) dimers as bridging ligands and two SCN bridges. Comparison of the lengths between the PCA dimers and 4,4'-bipyridine-type ligands demonstrated that a design strategy-the preparation of a bridging ligand through self-assembly of two PCAs is both efficient and particularly suitable for the preparation of very long bridging ligands.

Various proton-coupled electron transfer (PCET) driven catalytic processes has led to the construction of Hangman ligands bearing two rigid xanthene spacers functionalized with carboxylic acids and ester groups. Studies suggest that these Hangman platforms to support multielectron chemistry, which is established due to the proclivity of PCET to promote the catalytic disproportionation of hydrogen peroxide to oxygen and water via a high-valent metal oxo.

Heterochiral homo-oligomers with alternating backbone configurations are constructed by using the different enantiomers of the cis- and trans-2-aminocyclopentanecarboxylic acid (ACPC) monomers. Molecular modeling and the spectroscopic techniques unequivocally proved that the alternating heterochiral cis-ACPC sequences form an H10.12 helix, where extra stabilization can be achieved via the cyclic side chains.

The potential of the tetrabutylammonium-induced liquid--liquid-phase separation in alkyl carboxylic acid vesicular solutions for the extraction of organic compounds prior to liquid chromatography was examined for the first time. The behavior of the coacervates yielded from octanoic to oleic acids as a function of the pH and salts was investigated. The time required for phase separation depended on the length of the carboxylic acid alkyl chain and the experimental procedure (i.e., standing, sonication, centrifugation, stirring, etc.). Theoretical preconcentration factors were a function of both surfactant concentration and the length of the alkyl chain, and they greatly surpassed those obtained with other surfactant-mediated separations (e.g., surfactant-rich phases from dodecane-sulfonic acid or Triton X-114). Parameters affecting the extraction efficiency were assessed. Analytes in a wide polarity/charge range, (e.g., PAHs, surfactants, chlorophenols, bisphenols, phthalates, herbicides, amines, dyes, and photographic developers) were extracted with high efficiencies on the basis of the different types of interactions that the vesicular coacervates can establish (i.e., hydrophobic and ionic interactions, hydrogen bonds, and formation of mixed aggregates). The coacervates were compatible with the chromatographic determination of analytes following UV or MS detection. Their suitability for working under real conditions was checked by applying them to the extraction of nonionic surfactants [alkylphenol ethoxylates (octyl and nonyl) and alcohol ethoxylates ([C.sub.12]-[C.sub.16])] from raw and treated sewage and to fiver water samples. Analytes in the coacervate were separated and quantified by liquid chromatography-ion trap mass speca'ometry. No cleanup steps were necessary. Recoveries of the target compounds in the environmental water samples ranged from 89 to 103%.

Carborane-containing dendrons based on a 2,2-bis(hydroxymethyl)propanoic acid (bis-MPA) scaffold is prepared in boron neutron capture therapy. The structure of this dendron is simulated by molecular dynamics and a 10-carbon linker carrying carboxylic group is installed at the focal point of dendron to distance attached point from sterically hindered core.

We report a new method developed for the isolation and determination of low molecular weight dicarboxylic acids and related polar compounds ([C.sub.2]-[C.sub.9]) from seawater samples. The seawater sample was first acidified and then passed through an activated charcoal column to adsorb the dicarboxylic acids. They are then desorbed with N[H.sub.4]OH/methanol/water mixture and derivatized with B[F.sub.3]/1-butanol to dibutyl esters, which are determined using a capillary GC/FID. We tested different pH (0.5, 1, 1.5) and different amounts of charcoal (100, 200, 300, 500 mg) to maximize the recovery of dicarboxylic acids. Using 300 mg of activated charcoal for 100 mL of sodium chloride solution acidified at pH 1, the recoveries for [C.sub.2], [C.sub.3], [C.sub.4], [C.sub.5], [C.sub.6], [C.sub.7], [C.sub.8], and [C.sub.9] were 61, 49, 96, 84, 77, 67, 57, and 53%, respectively. We applied this method to real seawater samples collected from the northwestern Mediterranean Sea. Here, we report, for the first time, concentrations of a homologous series of [C.sub.2]-[C.sub.9] dicarboxylic acids as well as ketocarboxylic acids including glyoxylic and 4-oxobutanoic acids in surface water and deep seawater samples, with glyoxylic acid being the dominant species (8-40 [micro]g [L.sup.-1]). This method allows the detection of dicarbonyls such as glyoxal in the samples although its quantification is not possible.

UV photolysis of Fe(III)-aerobactin induces decarboxylation of the [alpha]-hydroxy carboxylic acid group of the citrate backbone of aerobactin, forming a 3-ketoglutarate moiety. The photoproduct retains the ability to coordinate iron (III) and it promotes iron acquisition by the source bacterium, Vibrio sp. DS40M5.

A contrastive study was carried out for the coordination chemistry of [H.sub.3]CAM and [H.sub.2]PDA based on a series of metal-organic framework. The reactions of [H.sub.3]CAM and Ln(III) salts or [Ln.sub.2][O.sub.3] gave different self-assembly processes and the products of different metal/ligand ratios with reactants were isolated for Ln(III) salts and hydroxyl groups coordinate with metal centers.

A description is provided of a mild protocol for the conversion of beta-ketoesters and beta-diketones to carboxylic acids with the use of cerium ammonium nitrate (CAN) in C(H.sub.3)CN. The existence of nitrate as an oxidant ligand or as an additive is crucial for success of the reaction.

The enol of 2-oxocyclobutanecarboxylic acid in aqueous solution is generated, which is then isomerized to the keto form of this acid. An investigation conducted shows that enol is an unexpectedly strong acid, a phenomenon that may be attributed to a remarkable acid-strengthening effect of cyclobutane ring.

A description is provided of an easy, direct, general and efficient samarium diiodide-mediated preparation of 3-hydroxyacids in high yield by reaction of different aldehydes or ketones with commercially available iodoacetic acid. Preparation of other derivatives from 3-hydroxyacids such as different esters and beta-lactones is also described.

A new nonempirical approach, based on circular dichroism (CD) spectroscopy, is developed for determining the absolute configuration (AC) of 2-substituted chiral carboxylic acids in solution. This approach has displayed its full validity with alkyl- and aryl-substituted acids, with alpha-hydroxy acids and alpha-amino acids, also showing that pi-pi arene-arene interactions can overcome steric interactions, even stabilizing the most sterically crowded conformers.

The rapid and selective photodimerization of 9-(N,N-dimethylaminomethyl)anthracene is achieved in the solid state by using salt formation with particular nonaromatic dicarboxylic acids. The crystal structures of these salts are used to rationalize their solid-state reactivities.

The synthesis of propargylic fluorohydrins under mild conditions from a readily available fluoropropargyl chloride is reported. Fluorohydrins can be oxidized to alpha-fluoroketones and alpha-fluorocarboxylic acids with Jones' reagent.

C,D-ring symmetric chlorins are prepared in 47-85% yield by condensation of appropriately substituted bis-formyldihydrodipyrrins and dipyrromethane biscarboxylic acids in 5% TFA/CH2Cl2. Target chlorins are used to investigate the effect of lipophilic and hydrophilic substituents on tissue partitioning and cellular membrane penetration in photodynamic therapy (PDT).

Kinetic resolution of 4-alkyl-2-aryl-5-oxo-4,5-dihydrooxazole-4-carboxylic acid esters (azlactones 1) were achieved by copper-DTBM-SEGPHOS catalyzed alcoholysis reaction with good selectivity. Variation of ee of unreacted substrates and products with conversion was found to follow the theoretical line of zeroth-order kinetic resolution, for which the selectivity profiles and graphical analysis were presented and the efficiency of resolution in zeroth-order reaction is higher than first order reaction.

The Na(super +)/dicarboxylate cotransporter 1(NaDC1) is a low-affinity transporter for citric acid cycle intermediates such as succinate and citrate. It is concluded that transmembrane 7, Pro-327 might be of particular importance in the function of the transporter, whereas Pro-351 might affect protein targeting and the prolines in transmembrane 10, at positions 523 and 524, might not be directly involved in the transporter function but might be necessary for maintaining structure.

A porous layer open tubular (PLOT) silica gel column was used together with subcritical C[O.sub.2] as the mobile phase to effect the group separation of polar oxygenated compounds. Aliphatic and aromatic compounds were shown to elute together. This group was followed by ethers and aldehydes, which were separated from compounds containing an alcohol functional group. Compounds with a carboxylic acid moiety could also be eluted from the silica gel. The group separation obtained when a silica gel PLOT column is used together with subcritical C[O.sub.2] was also demonstrated to be valuable as the first dimension of a comprehensive two-dimensional SFC x GC analysis where the GC analysis in the second dimension is performed with a fast and independently heated temperature programmed gas chromatograph. With this combination of SFC and GC, many of the oxygenated compounds, routinely found in petroleum samples, could successfully be separated and identified.

Identification of degradation products of environmental contaminants is a challenging task because not only are they present in very low concentrations but they are also mixed with complex matrixes that interfere with detection. This work illustrates a simple approach using ion trap mass spectrometry combined with H/D-exchange experiments to elucidate the structures of iopromide metabolites formed during biodegradafion in activated sludge. Iopromide is an X-ray contrast agent that has been detected frequently in effluents of wastewater treatment plants and in surface waters due to its persistence and high usage. Three metabolites produced by oxidation of the primary alcohols (forming carboxylates) on the side chains of iopromide were identified in a batch reactor with mixed liquor from a conventional activated sludge. Derivatization of the carboxylic acid to form a methyl ester and interpretation of the M[S.sup.2] data of this derivative aided in the confirmation of the identifies of these metabolites. Furthermore, one metabolite formed by dehydroxylation at the two side chains was identified in a batch reactor with mixed liquor from a nitrifying activated sludge. The M[S.sup.2] fragmentation pattern of iopromide and its metabolites revealed that the iodinated ring remains intact and that minor transformations in the structure occur during biodegradafion of iopromide in biological wastewater treatment plants.

A highly efficient strategy is developed for the rapid asymmetric synthesis of gem-dimethyl and spirocyclopropyl norbornyl carboxylic acids. The key transformation involved the unprecedented asymmetric Diels-Alder reaction of highly reaction beta,beta-cyclopropyl-alpha,beta-unsaturated N-acyloxazolidinoones with cyclopentadiene affording the adducts in high yield and de.

1,6- and 1,7-bis(n-octylamino)perylene-3,4:9,10-bis(dicarboximide) were synthesized by reaction of n-octylamine with the corresponding dibromo compounds that display intense charge-transfer optical transitions. The radical cations exhibit excellent stability at room temperature as shown by cyclic voltammetry, spectroelectrochemistry and electronic paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopy.

The reactions of a range of amide-stabilized sulfur ylides derived from camphor-derived sulfonium salts for the synthesis of glycidic amides are studied. Primary, secondary and tertiary amides are tested and it is found that the highest enantioselectives are observed with tertiary amides with exclusive trans selectivity, and the selective ring opening of the amides with a variety of nucleophiles is effected, followed by hydrolysis of the amide to yield the corresponding carboxylic acid.

A general and practical large-scale synthesis of hydroxyl acids that possess alkenyl and alkynyl appendages are reported. No variation are induced by substitution of only one ethyl group with a vinyl one, although the substitution of both ethyl groups with vinyl or acetylene appendages has the greatest effect on the molecular structure and results in different hydrogen-bonding motifs.

The reactions of a series of carboxylic acids, including acetic acid, acetic-d(sub 3) acid-d, and formic acid, on the Ge(100)-2 * 1 surface using a combination of experimental and theoretical techniques are studied. The carboxylic acids studied exhibit unexpected vibrational modes between 1400 and 1525 cm(super -1), which are attributed to the presence of a bidentate bridging structure where both oxygen atoms interact directly with the surface.