Identifizierung organischer Säuren durch thermische Analyse und Bestimmung des Säuregehaltes in Anhydriden

Zusammenfassung Ein thermisches Analysenverfahren wurde ausgearbeitet, das die Identifizierung einiger organischer Säuren nebeneinander und zugleich deren sehr empfindliche Bestimmung in kleinen Einwaagen ermöglicht. Die dazu entwickelte Anlage verwendet einen Gaschromatographendetektor.

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Identification of organic acids through thermoanalysis and determination of the acid content of anhydrides

Summary A thermoanalytic procedure has been developed which permits to identify several organic acids in the presence of one another, and at the same time to determine them in very small samples. The apparatus employs a gaschromatograph-detector.

     

Formic Acid as a Potential Pretreatment Agent for the Conversion of Sugarcane Bagasse to Bioethanol

In recent years, growing attention has been focused on the use of lignocellulosic biomass as a feedstock for the production of ethanol, a possible renewable alternative to fossil fuels. Several pretreatment processes have been developed for decreasing the biomass recalcitrance, but only a few of them seem to be promising. In this study, effect of various organic solvents and organic acids on the pretreatment of sugarcane bagasse was studied. Among the different organic acids and organic solvents tested, formic acid was found to be effective. Optimization of process parameters for formic acid pretreatment was carried out. The structural changes before and after pretreatment was investigated by scanning electron microscopy, X-ray diffraction (XRD), and Fourier transform infrared (FTIR) analysis. The X-ray diffraction profile showed that the degree of crystallinity was more for pretreated biomass than that of untreated. The FTIR spectra shown at the stretching of hydrogen bonds of pretreated sugarcane bagasse arose at higher number. It also revealed that the cellulose content in the solid residue increased because the hemicelluloses fraction in raw materials was released by acid hydrolytic reaction.     

Neue Synthesemethoden 2 Milde Einphasenoxidation von Aldehyden zu Carbonsäuren Kurze Mitteilung

The mild oxidation of aldehydes to carboxylic acids with benzyltriethylammoniumpermanganate in organic solvents at roomtemperature is presented.

     

Dünnschicht-chromatographische Untersuchung von dissoziierenden Verbindungen in programmierter gasphase

Zusammenfassung Der Einfluß der Gasphase auf die dünnschicht-chromatographischen Eigenschaften von organischen Säuren und Basen wurde in einer Vario KS Kammer untersucht. Dampfphasen-Vorbeladungen mit wäßriger Essigsäure- und Ammoniaklösung wurden vorgenommen. In Folge der Vorbeladung stellten sich unterschiedliche pH-Werte auf der DC-Platte ein, wodurch die Trennung der Verbindungen mit ähnlicher Struktur verbessert werden konnte. Die theoretischen Zusammenhänge werden diskutiert und die Bedeutung der Gasphasen-Vorbehandlung gezeigt.

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Thin-layer chromatographic investigation of organic acids and bases in a variable vapour phase

Summary The effect of the vapour phase on the TLC behaviour of organic acids and bases was investigated using a Vario KS chamber. Pre-saturation of the layer was performed with the vapour phase of aqueous acetic acid and ammonia. Pre-saturation resulted in different pH values on the TLC plates and, as a consequence, the separation of compounds of similar structures could be improved. Theoretical correlations are discussed and the importance of presaturation is stated.

     

Application of ion exclusion chromatography (IEC) for the determination of sugar and carboxylic acids in hydrolysates from carbohydrate containing residues

The oxidation of carbohydrate containing biomass residues by nitric acid yields several organic acids, especially sugar acids. To improve existing methods for the separation of such substance combinations by ion exclusion chromatography, the influence of temperature and eluant (proton) concentration on the retention behaviour and separation of 31 analytes belonging to substance groups like sugar acids, lactones, hydroxy-, mono- and polycarboxylic acids was checked with a Merck cation exchange column “Polyspher OA-HY”. By a combination of two Chromatographic parameter sets the Chromatographic versatility could be enhanced. The developed Chromatographic method is a useful tool for the analytical characterisation of organic acids in hydrolysates of biomass residues. Presented on the ANAKON ’95 as poster     

Zur Frage der katalytischen Wirksamkeit organischer Lewissäuren. Die Verätherung von Methanol durch Diazoessigester in Gegenwart organischer Lewissäuren Zur Kenntnis organischer Lewissäuren, 29. Mitt.

Zusammenfassung Organische Lewissäuren zeigen keinerlei Wirksamkeit als saure Katalysatoren. Ihre Reaktion mit Diazoessigester in Methanol nimmt einen komplexen Verlauf; die dabei auftretende Verätherung von Methanol unter Bildung von Methoxyessigester ist auf Allgemeine und Spezielle Brønstedsäurekatalyse durch Folgeprodukte zurückzuführen. Strukturmerkmale, die die Bevorzugung des Lewis- bzw. Brønstedsäurecharakters von Methylen-meldrumsäuren regeln, spielen dabei eine entscheidende Rolle.

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The catalytic activity of organic Lewis acids. Etherification of methanol with ethyl diazoacetate in the presence of organic Lewis acids. Organic Lewis acids, XXIX

Organic Lewis acids are completely without activity as acid catalysts. Their reaction with ethyl diazoacetate in methanol follows a complex path; the etherification of methanol with formation of ethyl methoxyacetate which occurs is due to general and specific Brønsted acid catalysis by secondary products. Structural characteristics which enhance the Lewis or Brønsted acid character of methylene Meldrum's acids play a decisive role.

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Mit 10 Abbildungen

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Herrn Prof. Dr. Dr. h. c.Otto Kratky zum 70. Geburtstag gewidmet. Die Autoren.

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28. Mitt.:Soledad Penades, H. Kisch, K. Tortschanoff, P. Margaretha undO. E. Polansky, Mh. Chem.104, 447 (1973).

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Teil der Diss.R. Neunteufel, Universität Wien 1972.     

Application of ion exclusion chromatography (IEC) for the determination of sugar and carboxylic acids in hydrolysates from carbohydrate containing residues

The oxidation of carbohydrate containing biomass residues by nitric acid yields several organic acids, especially sugar acids. To improve existing methods for the separation of such substance combinations by ion exclusion chromatography, the influence of temperature and eluant (proton) concentration on the retention behaviour and separation of 31 analytes belonging to substance groups like sugar acids, lactones, hydroxy-, mono- and polycarboxylic acids was checked with a Merck cation exchange column “Polyspher OA-HY”. By a combination of two chromatographic parameter sets the chromatographic versatility could be enhanced. The developed chromatographic method is a useful tool for the analytical characterisation of organic acids in hydrolysates of biomass residues. Received: 18 August 1995 / Revised: 26 March 1996 / Accepted: 1 April 1996     

Umsetzung elektrisch neutraler organischer Lewissäuren mit Hydrazin

Zusammenfassung Während verschiedene Basen mit organischen Lewissäuren stabile Anbadone liefern, führt die Umsetzung mit Hydrazin zu Aldazinen bzw. Hydrazonen.

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Reaction of electrically neutral organic lewis acids with hydrazine (organic lewis acids, XIV)

While several bases reacting with organic Lewis-acids form stable anbadons, the reaction with hydrazine leads to aldazines (azines) and hydrazones.

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13. Mitt.:P. Margaretha undO. E. Polansky, Mh. Chem.100, 576 (1969).     

Application of an indicating system of bismuth electrodes for the determination of organic bases and acids in nonaqueous solutions

Summary Tertiary amines and salts of organic acids have been titrated by means of perchloric acid applying a biamperometric indicating system consisting of a polarised or unpolarised pair of bismuth electrodes. Also, mono- and polycarboxylic acids, alone and in mixtures, have been determined with a strong base using the same end-point detection technique. The results obtained are in good agreement with those of potentiometry or catalytic thermometry.

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Anwendung eines Indikationssystems aus Wismutelektroden zur Bestimmung von organischen Basen und Säuren in nichtwäßrigen Lösungen

Zusammenfassung Tertiäre Amine und Salze organischer Säuren werden durch Titration mit einer Lösung von Perchlorsäure quantitativ bestimmt. Das verwendete Indicatorsystem besteht aus einem Paar polarisierter oder nichtpolarisierter Wismutelektroden. Das gleiche System wurde auch angewandt auf die titrimetrische Bestimmung von Mono- und Polycarbonsäuren mit einer starken Base. Die Ergebnisse stimmen gut mit denen der potentiometrischen bzw. katalytisch-thermometrischen Methode überein.

     

Homogeneous Degradation of Cellulose in Its Aqueous Solution at Mild Temperature under Atmospheric Pressure

Degradation of cellulose to chemicals is one of major routes for biomass conversion. Here, a new simple and two-step method has been developed to convert cellulose in its homogeneously alkaline solution to organic acids under atmospheric pressure at mild temperature. At first, cellulose was degraded to small molecular intermediates at 110 ℃ for 3 h under atmospheric pressure, and then it was oxidized with H₂O₂ at 50 ℃ for 4 h. Under the optimal condition, 73.5% conversion of cellulose could be achieved, and the yield of organic acids was 32.8% (formic acid), 11.6% (lactic acid), and 2.3% (oxalic acid), respectively. It is noteworthy that the new strategy reduces energy consumption in the process of reaction, unlike the hydrothermal reaction under high temperature and high pressure.     

Colorimetric studies of vanadium(V) with organic acids

Summary The intense yellow colour developed by adding an excess of organic acids (acetic, succinic, malonic, benzoic, phthalic) to an ammonium metavanadate solution is employed for the colorimetric determination of vanadium. On the other hand, the decrease in the intensity of the colour developed by acetic acid and metavanadate by oxalic and citric acids can be used for an indirect colorimetric determination of these acids.

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Zusammenfassung Die intensive Gelbfärbung, die Ammoniummetavanadat mit organischen Säuren (Essig-, Bernstein-, Malon-, Benzoe-, Phthalsäure) bildet, kann zu einer colorimetrischen Vanadiumbestimmung benutzt werden. Andererseits kann die Schwächung der aus Metavanadat und Essigsäure gebildeten Gelbfärbung durch Oxal- und Citronensäure zu einer indirekten colorimetrischen Bestimmung dieser Säuren herangezogen werden.

     

Quantenchemische Untersuchung von Protonierungs-und Deprotonierungsgleichgewichten

Zusammenfassung Unter Anwendung der Omega-HMO(Pi + Sigma)-Methode wird die Ladungsverteilung in Carbonsäuren, Alkoholen, Chinuclidinen und Phosphonsäuren berechnet. Die Nettoladung der aciden Wasserstoffatome von Carbonsäuren, Alkoholen und Phosphonsäuren zeigt eine lineare Beziehung zu den pK _a-Werten dieser Verbindungen. Die berechnete Nettoladung am Stickstoff-Atom der Chinuclidine kann zu deren Basizität in Beziehung gesetzt werden.

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Quantum chemical treatment of protonation and deprotonation equilibria

The charge distribution of organic acids, alcohols, chinuclidines and phosphonic acids has been calculated by the Omega-HMO(Pi + Sigma) method. A linear correlation was found between the net charge of the acidic hydrogen atoms of organic acids, alcohols and phosphonic acids and the acidity of these compounds. The calculated net charge of the nitrogen atom of chinuclidines is related to their basicity.

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Mit 4 Abbildungen     

Evaluation and Optimization of Organic Acid Pretreatment of Cotton Gin Waste for Enzymatic Hydrolysis and Bioethanol Production

This paper investigates the efficiency of the organic acids on the pretreatment of an industrially generated cotton gin waste for the removal of lignin, thereby releasing cellulose and hemicellulose as fermentable sugar components. Cotton gin waste was pretreated with various organic acids namely lactic acid, oxalic acid, citric acid, and maleic acid. Among these, maleic acid was found to be the most efficient producing maximum xylose sugar (126.05?±?0.74 g/g) at the optimum pretreatment condition of 150 °C, 500 mM, and 45 min. The pretreatment efficiency was comparable to the conventional dilute sulfuric acid pretreatment. A lignin removal of 88% was achieved by treating maleic acid pretreated biomass in a mixture of sodium sulfite and sodium chlorite. The pretreated biomass was further evaluated for the release of sugar by enzymatic hydrolysis and subsequently bioethanol production from hydrolysates. The maximum 686.13 g/g saccharification yield was achieved with maleic acid pretreated biomass which was slightly higher than the sulfuric acid (675.26 g/g) pretreated waste. The fermentation of mixed hydrolysates(41.75 g/l) produced 18.74 g/l bioethanol concentration with 2.25 g/l/h ethanol productivity and 0.48 g/g ethanol yield using sequential use of Saccharomyces cerevisiae and Pichia stipitis yeast strains. The production of bioethanol was higher than the ethanol produced using co-culture in comparison to sequential culture. Thus, it has been demonstrated that the maleic acid pretreatment and fermentation using sequential use of yeast strains are efficient for bioethanol production from cotton gin waste.     

Production of organic acids from biomass resources

Catalytic synthesis of valuable organic acids such as lactic acid, levulinic acid, formic acid, acetic acid, 2, 5-furandicarboxylic acid (FDCA), and sugar acids (e.g. gluconic acid and glucosaminic acid) from renewable carbon resources is of high interest for a sustainable chemical industry in the future. A number of efficient catalytic systems have been recently developed to convert biomass into organic acids. Herein we highlight new strategies and catalysts that are effective for the transformations. The mechanisms and catalyst functions involved in several typical reactions are analyzed for the rational design of more efficient catalytic systems.     

高效液相色谱法同时测定生物质乳酸发酵液中有机酸及糖类化合物

建立了高效液相色谱(HPLC)同时测定生物质乳酸发酵液中有机酸及糖类的分析方法。使用Bio-Rad Aminex HPX-87H色谱柱,以5 mmol/L的H2SO4为流动相,在柱温55 ℃,流速0.6 mL/min条件下,采用示差折光检测器进行检测。结果表明,该方法可在17 min内实现发酵液中各种有机酸和糖类化合物等的完全分离与定量,6种有机酸和3种糖类化合物在0.15～5.19 g/L范围内的线性关系良好,回归方程的线性相关系数在0.9998以上。将该法用于米根霉发酵液的检测,两个水平的加标回收率为96.91%～103.11%,相对标准偏差(n=6)为0.81%～4.61%。该法适用于微生物发酵液中多种有机酸和糖类的快速、高效分离和定量测定。     

Preparation of a graphene oxide/silica composite modified with nitro‐substituted tris(indolyl)methane as a solid‐phase extraction sorbent for the extraction of organic acids

This paper describes the use of graphene oxide/silica modified with nitro‐substituted tris(indolyl)methane as a solid‐phase extraction sorbent for the determination of organic acids. The resultant graphene oxide/silica modified with nitro‐substituted tris(indolyl)methane was characterized by FTIR spectroscopy and adsorption experiments. Solid‐phase extraction parameters such as sorbent type, sample solution pH, sample loading rate, eluent salt concentration, eluent methanol concentration, elution rate, sample loading, and elution volume were optimized. The method showed good precision, accuracy, sensitivity, and linear response for organic acids analysis over a concentration range of 1–100 μg/L for benzoic acid, p‐methoxybenzoic acid, and salicylic acid and 5–100 μg/L for the remaining organic acids (cinnamic acid, p‐chlorobenzoic acid, and p‐bromobenzoic acid) with coefficients of determination (r²) of higher than 0.9957. Limits of detection from 0.50 to 1.0 μg/L for six organic acids were achieved. The developed method was successfully applied to determine organic acids in real samples.     

Unterscheidung von Humins?uren und Ligninsulfons?uren durch zeitaufgel?ste Untergrundsignale in der Graphitrohr-AAS (Graphitrohr-Pyrolyse, UV-Pyrolyse-Spektrometrie)

Summary The computer-time-resolved background measurement in electrothermal AAS (graphite tube-AAS) is employed in order to achieve a differentiation in the substances of organic materials as well as a summary classification by pyrolytic behaviour. By way of example of various humic acids as well as lignin-sulphonic acid the differences in pyrolytic behaviour in UV gas-phase spectrometry is shown.     

Mikrotitration organischer Substanzen als sehr schwache S?uren nach DC-Trennung

Zusammenfassung Eine titerstabile Maßlösung von 0,005 N Kaliumhydroxid in Dimethylsulfoxid wird beschrieben. Da sehr viele organische Verbindungen als sehr schwache Säuren angesehen werden können, war es möglich dieses Reagens zur mikrotitrimetrischen DC-Auswertung einzusetzen. Nach der chromatographischen Trennung wird der betreffende Kieselgelfleck isoliert und die organische Substanz extrahiert. Anschließend wird mit 0,005 N KOH/DMSO potentiometrisch titriert. Damit kann die Bestimmung eines Wirkstoffes in einer Mischung mit hoher Genauigkeit durchgeführt werden. Keinerlei Vergleichssubstanz wird benötigt. Die maximale Abweichung vom Sollwert betrug 1%.

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Microtitrimetric determination of organic compounds as very weak acids after TLC separation

Summary A titer-stable solution of 0.005 N potassium hydroxide in dimethylsulphoxide is described. Because many organic compounds behave as very weak acids, an application of this reagent to the microtitrimetric evaluation of thin-layer chromatograms was possible. After chromatography the spot of silica gel is isolated and the organic compound is rapidly extracted. Then quantitation is carried out by direct potentiometric titration with 0.005 N KOH/DMSO solution. The analysis of an active ingredient in a mixture can readily be achieved with high accuracy. No standard compounds are necessary. Maximum deviation from theoretical values was 1%.

     

The optimization of the conversion of agricultural waste into volatile fatty acids under anaerobic conditions

The selection of a biocatalyst was performed and the first optimal microbial association was obtained. This association was capable of converting products of depolymerization of sawdust, straw, and lignin into volatile fatty acids with an acid-producing activity that was greater by 1.3 times than the initial methane activity. The largest percentages of butyric acid (40%) and ethanol (14%) were obtained from biomass out of straw in concentrations of soluble organic substances from 2.5 to 6.3 g_COD/L. Using biomass from sawdust and lignin at concentrations of organic substances from 4.0 to 8.0 g_COD/L and a duration of the conversion process of up to 18 days we obtained an output of butyric acid that was two times smaller than that on a biomass from straw.     

Auswertungen von Tetraphenyloboratniederschlägen. I

Zusammenfassung Durch starke Säuren werden Alkalitetraphenyloborate in Borsäure und ein Gemisch organischer Spaltprodukte zerlegt. Die entstehende Borsäure läßt sich in bekannter Weise mit 1,1-Dianthrimid photometrisch bestimmen. Eine Arbeitsvorschrift zur indirekten spektralphotometrischen Bestimmung von Kalium, Rubidium und Cäsium wird angegeben. Das Verfahren wurde statistisch und anhand von Beleganalysen geprüft.

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Evaluations of tetraphenyloborate precipitates

Summary The alkali tetraphenyloborates are decomposed by strong acids into boric acid and a mixture of organic fission products. The resulting boric acid can be determined photometrically in known manner with 1,1-dianthrimide. A working procedure for the indirect spectrophotometric determination of potassium, rubidium and cesium is given. The method was tested statistically and with reference to check analyses.