Determination of the Composition of Volatiles in Cognac (Brandy) by Headspace Gas Chromatography–Mass Spectrometry

A method for the quantitative determination of easily volatile compounds in cognac (brandy) by headspace gas chromatography–mass spectrometry was developed. Alcohols and carboxylic acid aldehydes, acetals, and ethylates were identified by comparing their mass spectra with those presented in the Wiley database, and by comparing their relative retention times with those of reference materials of the known composition. Detection limits for test compounds ranged from 0.02 to 0.2 mg/L. Statistically valid difference in the concentration of compounds with different aromas or specific odors was demonstrated for cognacs aged for 3, 10, and 20 years. The concentration of cognac-flavored compounds, such as diethylacetal and carboxylic acid esters, for example, ethyl formate, significantly increased with age, whereas the concentration of alcohols (butanols, allyl alcohol, hexenol, and toxic methanol) considerably decreased. Comparison analyses of some Armenian, Moldavian, Georgian, Ukrainian, Russian, Kyrgyz, and French cognacs were carried out.     

Electrospray mass spectral fragmentation study of N,N′-disubstituted imidazolium ionic liquids

The tandem positive electrospray mass spectrometry (ESMS(n)) fragmentation of ionic liquids incorporating the 1-methyl-imidazolium ring substituted on N(II) with an alkyl chain functionalized with an alcohol, carboxylic acid, or an iodobenzyl or iodobenzoyl ester is presented for the first time. The influence of chain length and function is studied. Esterified structures led to intense CID fragments lacking the imidazolium ring allowing full characterization of the ester moiety. Fragment ion compositions for this interesting and newly important class of compounds are established through accurate mass data and deuterium labeling. The presence of the cationic ring system produces intense even electron molecular cations in electrospray that undergo multiple stages of CID to yield fragments which often are radical cations. Unusual losses of methyl and hydrogen radicals are frequently noted.     

Derivatisation for liquid chromatography/electrospray mass spectrometry: synthesis of pyridinium compounds and their amine and carboxylic acid derivatives

A simple method has been developed for the pre-column derivatisation of low molecular weight primary and secondary amines and carboxylic acids using quaternary nitrogen compounds to enhance their detection by liquid chromatography/electrospray ionisation mass spectrometry (LC/ESI-MS). The synthesis of seven novel quaternary nitrogen reagents is described. The derivatives are designed to be relatively small molecules to avoid some of the steric hindrance problems that may be associated with larger derivatisation reagents. The compounds have amine and carboxylic acid functional groups with which to derivatise carboxylic acids and amines, respectively. Two of the compounds contain a bromine atom in order to assess the advantages of a bromine isotope pattern in the mass spectra. This acts as a simple marker for derivatisation and enables data processing by cluster analysis.Activation of the carboxylic acid group was achieved by the use of either 1-chloro-4-methylpyridinium iodide (CMPI) or the more reactive 1-fluoro-4-methylpyridinium p-toluenesulphonate (FMP).1 Using both of these active reagents, the degree of nucleophilic substitution was investigated for the derivatisation of a variety of small molecules. Whilst giving some increase in the ESI-MS response for the derivatised compounds, the FMP itself acted as a derivatising reagent in a competing reaction. In the light of this finding, FMP was reacted with the test compounds separately and gave positive results as a derivatising reagent. Detection of the 'pre-charged' derivatives of amines and carboxylic acids by LC/ESI-MS was investigated with respect to their ESI response and chromatography.     

Investigation of the formation of poly(ethylene terephthalate) with model molecules: Kinetics and mechanism of the catalytic esterification and alcoholysis reactions. I. Carboxylic acid catalysis (monofunctional reactants)

Monofunctional compounds (benzoic acid, heptyl alcohol, and 2-butoxy-ethanol) were used to investigate the kinetics of the esterification and the alcoholysis reactions. Carboxylic acids (benzoic acid) are the only catalysts present in the reaction medium. The factors which influence the kinetics of the esterification reaction were studied: the nature of the carboxylic acid (substituents on the benzene ring), the nature of the alcohol, the composition of the reaction medium (alcohol alone or with another solvent, ester, or water). The results point out for an acyl type (A_AC2) mechanism. The alcoholysis reaction needs the presence of carboxylic acid as a catalyst to occur significantly. A similar mechanism is proposed for both reactions: nucleophilic attack by the oxygen atom of the alcohol at the ion pair formed by protonation of the acid (esterification reaction) or by protonation of the ester (alcoholysis).     

Mechanism of lactide polymerization in the presence of stannous octoate: The effect of hydroxy and carboxylic acid substances

The effect of hydroxy and carboxylic acid substances on lactide polymerization in the presence of stannous octoate was investigated. A polymerization mechanism was postulated to attempt to explain the controversies existing in the literature and also to explain our experimental observations. Stannous alkoxide, a reaction product between stannous octoate and alcohol, is proposed as the substance initiating the polymerization through coordinative insertion of lactide. Alcohol can affect the polymerization through the reactions of initiator formation, chain transfer, and transesterfication. Carboxylic acid affects the polymerization through a deactivation reaction. Experiments showed that alcohol increased PLLA production rate while carboxylic acid decreased it. Both alcohol and carboxylic acid reduced PLLA final molecular weight. The higher the alcohol concentration, the lower the polymer molecular weight. However, the final molecular weight of PLLA was not sensitive to the carboxylic acid concentration. A polymerization induction period was observed at high carboxylic acid concentration, due to the deactivation reaction caused by carboxylic acid. © 1994 John Wiley & Sons, Inc.     

On-line determination of carboxylic acids, aldehydes and ketones by high-performance liquid chromatography-diode array detection-atmospheric pressure chemical ionisation mass spectrometry after derivatization with 2-nitrophenylhydrazine

2-Nitrophenylhydrazine (2-NPH) is widely used for the derivatization of carboxylic acids, aldehydes and ketones, in industrial and biological samples. These compounds react with 2-NPH to form derivatives, which are separated by high-performance liquid chromatography (HPLC) and detected with diode array detection (DAD). The UV spectra give information about the functionality of the compounds: carboxylic acid or ketone/aldehyde. Most of the eluting compounds in "known" samples are well characterised by the retention time (comparison with those of standards) of the 2-NPH derivative and their UV spectrum. The identification of different unknown 2-NPH derivatives of carboxylic acids, ketones and/or aldehydes, in industrial or biological samples, based on retention time and/or UV spectrum is not sufficient. These unknown 2-NPH compounds can be identified with on-line atmospheric pressure chemical ionisation mass spectrometry (APCI-MS) based on the molecular mass or/and the fragmentation of the derivative. A novel and specific on-line HPLC-DAD-APCI(-)-MS method is described for the determination of carboxylic acids, ketones and aldehydes, after on-line pre-column derivatization with 2-NHP. The fragmentation of different 2-NPH derivatives were investigated and the possibilities of APCI(-)-MS detection were demonstrated by the on-line identification of an unknown derivative, which turned out to be a side product between 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 2-NPH in the presence of high concentrations of a cyclic amide in the sample solution.     

纳米尺度氧化石墨烯层作为高效碳催化剂用于苄醇与芳香醛的绿色氧化

合成了纳米尺度氧化石墨烯(NGO)层,用作碳催化剂高效催化苄醇与芳香醛的氧化反应.对于醇氧化反应,当80℃时H2O2存在下,NGOs(20 wt％)可高效催化醇选择性生成醛,其反应速率和产率取决于醇上取代基的性质.对于4-硝基苄醇,反应24 h后,只有10％可转换为相应羧酸.相反,4-甲氧基苄醇和二苯基甲醇分别反应仅9和3h则可完全转化为对应的羧酸和酮.NGO碳催化剂上芳香醛氧化速率高于醇氧化速率.对于所有的醛,采用7 wt％ NGO作催化剂,在70℃反应2-3 h后,就可完全转化为相应羧酸.我们讨论了NGO催化剂结构对苄醇和芳香醛氧化反应影响的可能机理.     

Synthese von neuen bifunktionellen Maleinimidverbindungen zur Herstellung von Chemoimmunokonjugaten

Summary Bifunctional maleimide compounds are suitable for binding small molecules to carrier proteins in that they bind to the sulfhydryl group of proteins through the double bond of the maleimide group and to molecules of low molecular weight (e.g. anticancer drugs) through a functional groupX. 18 maleimide compounds of the general formula Maleimid-R-X (R=phenylene, benzyl-, methylene-, ethylene, or am-benzoylethylamide group andX=hydroxy-, amino-, hydrazino-, carboxylic acid-, carboxylic anhydride-, carboxylic acid chloride-, carboxylic acid hydrazide-, oxycarbonylchloride-, aldehyde, keto-, orp-toluenesulfonate-group) were synthesized and characterized through¹H- and¹³C-NMR-spectroscopy, elemental analysis, and mass spectrometry.

     

FTIR investigation of interactions in blends of PMMA with a styrene/acrylic acid copolymer and their analogs

Fourier-transform infrared (FTIR) spectroscopy was used to examine the interactions in miscible blends of a styrene (92%)/acrylic acid (8%) copolymer (SAA8) with poly(methyl methacrylate) (PMMA). From the residue or interaction spectra and shifts of carbonyl and carboxylic acid stretching bands, it is concluded that there is a significant specific interaction involving hydrogen bonding between the carbonyl groups of the PMMA and the carboxylic groups of the SAA8. Similar FTIR spectra of some low-molecular-weight liquid analogs for the various monomer units of these polymers do not indicate a comparable interaction. This explains why direct calorimetry with these compounds fails to model correctly the expected exothermic mixing of the blends. Furthermore, the role of the aromatic moiety in the SAA polymer appears to reduce the degree of self-association of the carboxylic acid groups based on results for the model compounds. Coupled with molecular rigidity, the above mechanism makes the carboxylic acid units in SAA8 more available for interaction with the PMMA carbonyls.     

Gas-chromatographic determination of carboxylic acid anhydrides in oxidation products of alcohols and other organic compounds

A procedure was developed for the gas-chromatographic determination of carboxylic acid anhydrides in the composition of oxidation products of organic compounds after their conversion into alkyl formate by formic acid and benzyl alcohol or other primary alcohol introduced into the reaction medium. The reaction proceeds through the mixed anhydride, which is formed in situ from formic acid and the determined anhydride and is predominantly transformed into the corresponding alkyl formate in alcoholysis with alcohol. The potentialities of the procedure were illustrated by the determination of anhydrides in oxidation products of cyclohexane, cyclohexanone, and cyclohexanol.     

Ultratrace determination of highly hydrophilic compounds by 2,2,3,3,4,4,5,5-octafluoropentyl chloroformate-mediated derivatization directly in water

Highly hydrophilic compounds, with multiple carboxylic, hydroxylic, or aminic groups, have been determined at ultratrace level (3–30 fmol injected) in aqueous solution by direct derivatization with 2,2,3,3,4,4,5,5-octafluoropentyl chloroformate, followed by n-hexane extraction and analysis by gas chromatography-electron capture negative ion mass spectrometry (GC-ECNI-MS). The products have high molecular weights, but also high volatility, making their elution from the GC column efficient. The derivatizing agent was synthesized from the corresponding alcohol and phosgene. The derivatization reaction is catalyzed by a pyridine solution of N,N-dicyclohexylcarbodiimide. At 200 °C ion-source temperature, most negative ion mass spectra showed only a weak or no molecular ion, but a controlled and interpretable fragmentation, allowing the derivatives to be easily monitored by high-mass ion chromatograms. Typical distinctive fragments are located in the m/z 500–800 mass range. Optimization of the operating conditions for the derivatization was performed. This was done in order to minimize number and intensity of peaks due to the hydrolysis of chloroformate in the total ion chromatogram. Calibration curves proved linear over two orders of magnitude concentration.     

Derivatization of small biomolecules for optimized matrix-assisted laser desorption/ionization mass spectrometry

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) is a powerful tool for the measurement of low molecular mass compounds of biological interest. The limitations for this method are the volatility of many analytes, possible interference with matrix signals or bad ionization or desorption behavior of the compounds. We investigated the application of well-known and straightforward one-pot derivatization procedures to circumvent these problems. The derivatizations tested allow the measurement and the labeling of alcohols, aldehydes and ketones, carboxylic acids, alpha-ketocarboxylic acids and amines.     

Structural elucidation of monoterpene oxidation products by ion trap fragmentation using on-line atmospheric pressure chemical ionisation mass spectrometry in the negative ion mode.

Based on ion trap mass spectrometry, an on-line method is described which provides valuable information on the molecular composition of structurally complex organic aerosols. The investigated aerosols were generated from the gas-phase ozonolysis of various C(10)H(16)-terpenes (alpha-pinene, beta-pinene, 3-carene, sabinene, limonene), and directly introduced into the ion source of the mass spectrometer. Negative ion chemical ionisation at atmospheric pressure (APCI(-)) enabled the detection of multifunctional carboxylic acid products by combining inherent sensitivity and molecular weight information. Sequential low-energy collision-induced product ion fragmentation experiments (MS(n)) were performed in order to elucidate characteristic decomposition pathways of the compounds. Dicarboxylic acids, oxocarboxylic acids and hydroxyketocarboxylic acid products could be clearly distinguished by multistage on-line MS. Furthermore, sabinonic acid and two C(9)-ether compounds were tentatively identified for the first time by applying on-line APCI(-)-MS(n).     

（R）—N—乙酰四氢噻唑—2—硫酮—4—羧酸与醇的反应

（Ｒ）－Ｎ－乙酰四氢噻唑－２－硫酮－４－羧酸与醇反应，在ＳＯＣｌ２存在下得到乙酸酯及四氢噻唑－２－硫酮－４－羧酸酯；在碳酸钾存在下得到乙酸酯及四氢噻唑－２－硫酮－４－羧酸；在二环己基碳二亚胺（ＤＣＣ）存在下得到缩水产物Ｎ－乙酰四氢噻唑－２－硫酮－４－羧酸酯。     

Chromium(VI) oxide oxidation of non‐ethoxylated and ethoxylated alcohols for determination by electrospray ionization mass spectrometry

A new derivatization procedure to increase the sensitivity of electrospray ionization mass spectrometry (ESI‐MS) to non‐ethoxylated and ethoxylated alcohols was investigated. The analytes were oxidized with chromium(VI) oxide and the resulting carboxylic and ethoxy‐carboxylic acids were isolated by extraction with ethyl acetate; the extracts were alkalinized and infused into the ESI‐MS system working in the negative‐ion mode. The yields of the combined oxidation‐extraction were ca. 100% for non‐ethoxylated fatty alcohols dissolved in acetone and they decreased moderately in samples containing increasing amounts of water (e.g., a 75% yield was obtained with 50% water). Ethoxylated alcohols with more than two ethylene oxide units resulted in yields of ca. 60%. Low limits of detection (LODs) were obtained when the procedure was applied to the analysis of body‐care products and cosmetics containing fatty alcohols, e.g., in a varicose‐vein cream, the LODs were 25 µg cetyl alcohol and 7.5 µg stearyl alcohol (detected as palmitic acid and stearic acid, respectively) per gram of sample. High molecular mass alcohols were also detected in seawater after pre‐concentration by solid‐phase extraction. Thus, the proposed method is particularly valuable for use in industrial samples having complex matrices and in environmental samples and it is competitive with other methods for the analysis of trace amounts of fatty alcohols. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis,characterization and spectral studies of various newer 4‐benzyloxy‐1H‐indole‐2‐carboxylic acid (arylidene)‐hydrazides

4‐Benzyloxyindole‐2‐carboxylic acid hydrazide reacts with aromatic and heterocyclic aldehydes in alcoholic medium in refluxing conditions to give 4‐benzyloxy‐1H‐indole‐2‐carboxylic acid (arylidene)‐hydrazides, important synthetic intermediates for the synthesis of a newer class of pharmacologically active compounds. We describe here the synthesis of various 4‐benzyloxy‐1H‐indole‐2‐carboxylic acid (arylidene)‐hydrazides by conventional as well as microwave irradiation techniques. The structures of these compounds have been confirmed by spectroscopic techniques (FTIR, NMR and MS). Some of the interesting features of the electron impact mass spectral fragmentation pattern of these compounds are also discussed.     

Versatile and practical chiral shift reagent with hydrogen-bond donor/acceptor sites in a macrocyclic cavity

[structure: see text] Bifunctional macrocycle 1 with C2 symmetry was newly synthesized. NMR studies demonstrated that receptor 1 functions as a chiral shift reagent (solvating agent) that is highly effective for a wide range of chiral compounds having a carboxylic acid, oxazolidinone, lactone, alcohol, sulfoxide, sulfoximine, isocyanate, or epoxide functionality. Binding constants were determined to investigate the binding behavior of 1.     

A highly directional fourfold hydrogen-bonding motif for supramolecular structures through self-assembly of fullerodendrimers

Supramolecular dendrimers resulting from the dimerization of fullerene-functionalized dendrons through a quadruple hydrogen-bonding motif were prepared. The synthetic strategy is based on the esterification of a tert-butoxycarbonyl (Boc)-protected 2-ureido-4-[1H]pyrimidinone precursor possessing an alcohol function with fullerodendrons bearing a carboxylic acid unit at the focal point. Subsequent acidic treatment to cleave the protecting group and reaction of the resulting amine with octylisocyanate affords the targeted compounds. As demonstrated by the results of MALDI-TOF mass spectrometry and 1H NMR spectroscopy, both of the 2-ureido-4-[1H]pyrimidinone derivatives form self-assembled dimers spontaneously through hydrogen-bonding interactions, thus leading to supramolecular structures containing two or ten fullerene moieties.     

Characterization of rat liver microsomal and hepatocytal metabolites of brevetoxins by liquid chromatography–electrospray tandem mass spectrometry

Brevetoxins are natural neurotoxins that are produced by “red tide” algae. This class of compounds can cause neurotoxic shellfish poisoning and other health problems. Brevetoxin-2 is the most abundant among the nine brevetoxins that have been characterized, whereas brevetoxin-1 is the most toxic. In this study, brevetoxin-1 and brevetoxin-2 were incubated with rat liver hepatocytes and rat liver microsomes, respectively. After clean-up steps were taken to remove the proteins, samples were analyzed by liquid chromatography (LC) coupled with electrospray mass spectrometry (LC-MS). After incubation of brevetoxin-1, two metabolites were found: brevetoxin-1-M1 (molecular weight = 900 Da), and brevetoxin-1-M2 (molecular weight = 884 Da). The increase in molecular weight combined with evidence from tandem mass spectrometry showing an increased tendency for loss of water molecules, along with considerations of established precedents for chemical transformations led to the conclusion that brevetoxin-1-M1 was formed by converting one double bond in the E or F ring of brevetoxin-1 into a diol. The second metabolite (brevetoxin-1-M2) is proposed to be a hydrolysis product of brevetoxin-1 involving opening of the lactone ring with the addition of a water molecule. The incubation study of the other starting compound, brevetoxin-2, found two metabolites in the LC-ES-MS selected ion chromatogram. Brevetoxin-2-M1 (molecular weight = 912 Da) gave a large [M−H]⁻ peak at m/z 911, and its product ion mass spectrum allowed the deduction that this metabolite was the hydrolysis product of brevetoxin-2 involving conversion of the lactone to a carboxylic acid and an alcohol. The second metabolite (brevetoxin-2-M2, molecular weight = 896 Da) was deduced to have the same structure as that of brevetoxin-3 based on identical chromatographic retention times and similar mass spectra as those obtained for a brevetoxin-3 standard.     

Isomerization studies—I : Conversion of linear acids into their isomeric branched-chain analogues

The transformation of linear saturated carboxylic acid chlorides (i.e., stearoyl chloride) into mixtures of isomeric, highly branched acids, each having the same molecular weight as the starting material, was investigated. The fatty acid backbone was modified in either a two or three step process generally with excellent overall yield. In both procedures, the first step was catalytic decarbonylation of the acid chloride, which yielded a hydrocarbon monoene mixture having one less carbon atom than the starting acid. The monoene mixtures were reconverted to the branched acid derivatives by either the Koch reaction or the hydroformylation oxidative procedure. Products were designated as either dior trisubstituted carboxylic acids, on the basis of mass spectroscopic and GLC data.