Spectrophotometric determination and kinetic studies of condensation of aromatic aldehydes with 1,3-dimethylbarbituric acid

The condensation reaction of 1,3-dimethylbarbituric acid with aromatic aldehydes in ethanol has been investigated spectrophotometrically at 25–35°C. The reaction follows overall second-order kinetics, first-order each in reactant. From the dependence of the rate constants on temperature, activation parameters have been calculated. The rate of condensation increases with the presence of electron donating groups on the aromatic ring of the aldehyde. The rate-determining step involves dehydration of the aldol intermediate. The reaction was found to be catalyzed by HCl solutions. Based on this reaction, determination of 10 aromatic aldehydes in a concentration range of 0.13–70.25 μg/ml is proposed. The method was applied for determination of barbituric and 1,3-dimethylbarbituric acids also.     

Kinetics of the formation of pantolactone from pantothenates and its quantitative determination

The conditions of hydrolysis and lactonization of the calcium and sodium salts of pantothenic and pantoic acids have been studied. The selected conditions of hydrolysis (t=80°C, C_HCl=13%) led to a 100% yield of -alanine and pantothenates after 60 min from the beginning of hydrolysis, while the formation of pantolactone was complete in 105 min for the calcium salt and in 75 min for the sodium salt. The hydrolysis and lactonization reactions have been performed under the conditions mentioned, and the GLC of the pantolactone formed has permitted the determination of various concentrations of calcium pantothenate. The results obtained from the GLC analysis of pantolactone indicate the possibility of a quantitative determination of salts of pantothenic and pantoic acids. The sensitivity of this method is 0.2–5 nmole.Department of Metabolic Regulation, Academy of Sciences of the Belorussian SSR, Grodno. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 93–95, January–February, 1984.     

Synthesis of bis-α-amino acids through proline catalyzed asymmetric α-amination of higher homologs of Garner's aldehyde

A very convenient synthesis of bis-α-amino acids from the higher homologs of Garner's aldehyde is reported. The key step is proline catalyzed asymmetric amination of the aldehydes using dibenzylazodicarboxylate. The aldehydes used are either commercially available or can easily be prepared from aspartic or glutamic acid. One of the two chiral centers in the bis-amino acids comes from the aldehyde and the other one is generated through the proline catalyzed reaction, which were high yielding and proceeded with very high diastereoselectivity (93–99%). The reported route offers a general method for the synthesis of the title compounds with desired stereochemical outcome.     

Fluorometric determination of aromatic aldehydes with 1,2-Diaminonaphthalene

A new fluorometric method for the determination of aldehydes is presented. 1,2-Diaminonaphthalene reacts with aldehyde in dilute sulphuric acid to give a compound which fluoresces intensely in alkaline medium. The fluorescences produced from aromatic aldehydes in this method are fairly characteristic of individual aldehydes and their intensities are generally higher than those of fluorescences from aliphatic aldehydes. The only interference is from 2-oxo acids. The method may be suitable for the determination of aldehyde in complex samples.     

Addition of aldehydes to alpha-olefins,induced by oxygen in the presence of acetic anhydride

Conclusions A method was developed for synthesizing aliphatic ketones by radical addition of aldehydes to olefins without the addition of peroxide and consisting of bubbling of air through a mixture of aldehyde, olefin, and acetic anhydride at 70–85°.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 1846–1848, October, 1966.     

Determination of water in furfural by infrared spectroscopy

The IR absorption band at 5250 cm^–1 is used to determine 0–5% water in furfural. The accuracy of the determination is not less than 5%. The method is suitable for any kind of furfural. The analytical results are unaffected by the presence of formic, acetic, and pyromucic acids, and methanol and ethanol.     

Analysis of the compounds in the synthesis mixtures of hydroxy acids by a gradient programmed RP-HPLC with UV/vis and RI detectors

Summary A gradient programmed reversed phase high-performance liquid chromatographic (RP-HPLC) method is described for the quantitative determination of some aldehydes, hydroxy aldehydes, unsaturated aldehydes, hydroxy carboxylic acids, carboxylic acids, alcohols and polyols using an ultraviolet and a refractive index detector in series. The sample matrices are synthesis mixtures of hydroxy carboxylic acids. The structures of the hydroxy aldehyde intermediates are determined by¹³C NMR and the influence of sample preparation on analysis results is discussed. The limits of detection and the precision of the method are evaluated.     

Determination of linear aliphatic aldehydes in heavy metal containing waters by high-performance liquid chromatography using 2,4-dinitrophenylhydrazine derivatization

A simple and sensitive method is described for the determination of picomolar amounts of C₁–C₉ linear aliphatic aldehydes in waters containing heavy metal ions. In this method, aldehydes were first derivatized with 2,4-dinitrophenylhydrazine (DNPH) at optimized pH 1.8 for 30 min and analyzed by HPLC with UV detector at 365 nm. Factors affecting the derivatization reaction of aldehydes and DNPH were investigated. Cupric ion, an example of heavy metals, is a common oxidative reagent, which may oxidize DNPH and greatly interfere with the determination of aldehydes. EDTA was used to effectively mask the interferences by heavy metal ions. The method detection limits for direct injection of derivatized most aldehydes except formaldehyde were of the order of 7–28 nM. The detection limit can be further lowered by using off-line C₁₈ adsorption cartridge enrichment. The recoveries of C₁–C₉ aldehydes were 93–115% with a relative standard deviation of 3.6–8.1% at the 0.1 μM level for aldehydes. The HPLC–DNPH method has been applied for determining aldehyde photoproducts from Cu(II)–amino acid complex systems.     

Oxidation of 1-(4-nitrophenyl)-2-formylpyrrole

Pyrrole aldehydes interact with oxidizing agents to yield products which are oxidized to different degrees. Pyrrolecarboxylic acids are formed under the influence of silver oxides, an alkaline solution of permanganate, and 2–10% sulfuric acid [1–3]. With peroxidation of hydrogen, 5-unsubstituted pyrrole aldehydes convert to pyrrolone [4], and pyrrol-2-aldehyde converts to succinimide [5]. Chromacetate and chromium sulfuric acids oxidize pyrrole aldehydes to maleinimides [3].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 495–499, April, 1982.     

Simple and sensitive assay for nucleic acids by use of the resonance light-scattering technique with copper phthalocyanine tetrasulfonic acid in the presence of cetyltrimethylammonium bromide

On the basis of enhancement of resonance light scattering (RLS) of copper phthalocyanine tetrasulfonic acid (CuTSPc) by nucleic acids and cetyltrimethylammonium bromide (CTMAB) under suitable conditions, a new RLS method for determination of nucleic acids in aqueous solutions has been developed. At pH 9.80–10.95 and ionic strength 0.01 mol L^–1 (NaCl), the interaction of copper phthalocyanine tetrasulfonic acid with nucleic acids in the presence of cetyltrimethylammonium bromide results in enhanced RLS signals at 282.0 nm, 383.6 nm, and 616.2 nm in the enhanced regions. It was found that the enhanced RLS intensity at 383.6 nm was proportional to the concentration of nucleic acids within suitable ranges. The limits of detection were 10.6 ng mL^–1 for fish sperm DNA and 32.4 ng mL^–1 for calf thymus DNA when the concentration of copper phthalocyanine tetrasulfonic acid was 2.0×10^–6 mol L^–1. This method is rapid, simple and sensitive. In addition, the reagents used are relatively inexpensive, stable, and easily synthesised. The method can be applied to the determination of nucleic acids in the presence of coexisting substances, and we have applied it to the determination of DNA in synthetic samples, with satisfactory results.     

Fatty aldehydes of the phosphatidylethanolamines of marine invertebrates

The compositions of the fatty aldehydes from the phosphatidylethanolamines of 26 species of marine invertebrates belonging to nine classes of six types have been investigated. It has been shown that for the aldehydes of all the animals investigated a high degree of saturation and the presence of substantial amounts of branched aldehydes and aldehydes with odd numbers of carbon atoms in the chain of the molecule are characteristic. The amounts of the main — 16:0, 18:0, 18:1, and 20:1 — aldehydes changes appreciably according to the systematic position occupied by the animal; the nature of their distribution can serve to a certain extent as a chemotaxonomic marker. The bryozoanBugula neritina differs from all the other animals studied by an unusually high content of the 17:0 aldehyde and the almost complete absence of unsaturated aldehydes.Institute of Marine Biology, Far Eastern Branch, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 621–625, September–October, 1989.     

Determination of uronic acids in natural materials by the decarboxylation method

Summary A preferred variant of the decarboxylation method for the determination of uronic acids is proposed which uses 57% hydriodic acid and the direct nonaqueous titration of the CO₂ formed. The range of concentrations of uronic acids that can be determined is from 2 to 100 µM. The sensitivity of the method is 1.5 µM, its reproducibility 0.6%, and the time of one determination 40–50 min. The proposed variant of the method is applicable to the study of various polysaccharides and other carbohy drate-containing biopolymers.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center of the Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 10–13, January–February, 1976.     

Short-term measurements of acrolein in ambient air

Summary A method has been developed for the determination of acrolein in air samples collected by a high-volume aqueous scrubber. The aldehyde is collected as the bisulfite adduct, which is decomposed before determination of acrolein by DNPH (2,4-dinitrophenylhydrazine) derivatization and HPLC. Approximately 95% of the acrolein reacts with DNPH within 3 h at DNPH:HSO₃ molar ratios of up to 10. The method appears promising for short-term air sampling at 8 L min^–1, enabling the achievement of a detection limit of 0.2 g m^–3 for acrolein.     

Gas chromatographic determination of serum bile acids — Application of a novel extraction procedure

Summary The profile of serum bile acids is a result of their liver metabolism and enterohepatic circulation.In the present work size exclusion chromatography is used for extraction of serum bile acids to optimize the methodology for analyzing serum bile acids by high resolution gas chromatography.Compared to other extraction methods like adsorption-[1–3] or reversed phase chromatography [4,5], this novel technique yielded a satisfactory recovery (75–104%) with high reproducibility. Therefore a reliable determination of serum bile acids is possible.     

PVC Membrane electrode for trinitrobenzenesulfonate and its use for indirect determination of amino acids

A PVC membrane electrode of the conventional type was prepared which is selective for trinitrobenzenesulfonate (TNBS^–). It showed a rapid Nernstian response within the TNBS^– concentration range 1.0 × 10^–5 to 1.0 × 10^–2 M at 25 ± 0.1°C. The electrode was selective, precise (RSD < 0.87% for TNBS^– and < 1.32% for amino acids) and usable within the pH range 2.5–12. The standard electrode potentials,E°, were determined at different temperatures and used to calculate the isothermal temperature coefficient of the cell. Selectivity coefficients for numerous compounds are given. The electrode has been used for the direct determination of trinitrobenzenesulfonic acid in aqueous solutions either by the standard additions method or by potentiometric titration against cetyltrimethylammonium bromide (CTABr) at pH 7. The electrode has been also applied successfully for the indirect microdetermination of neutral, acidic and basic amino acids separately, and as binary or ternary mixtures of neutral amino-acids. Total amino acids were determined in urine samples.     

Individual and simultaneous determination of ephedrine and phenylephrine by use of kinetic methodology

Kinetic methodology was for the first time used to develop a simple photometric method for the determination for ephedrine and phenylephrine using the stopped-flow mixing technique. The method involves oxidation of these compounds and kinetic monitoring of the reactions of the aldehydes formed with 2-methylbenzothiazoline-2-one hydrazone in the presence of iron (III) chloride to give the corresponding coloured formazans. Ephedrine and phenylephrine can be determined simultaneously by applying the proportional-equation method to the reaction rate and absorbance amplitude of the kinetic curves obtained for each analyte. The calibration graph was linear over the range 0.7–70.0 g mL^–1 ephedrine and 1.2–70.0 g mL^–1 phenylephrine. The proposed method was applied to the determination of ephedrine in pharmaceutical samples with a mean recovery of 103.2%. Synthetic mixtures of ephedrine and phenylephrine in ratios between 3:1 and 1:5 were satisfactorily resolved.     

Voltammetric Determination of Maleic and Fumaric Acids at an In Situ Renewed Graphite Electrode

It was shown that a graphite electrode renewed by cutting a thin surface layer immediately before each measurement can be used for the voltammetric determination of maleic and fumaric acids. The mechanical renewal of the electrode by polishing did not give a reliable signal. The relative standard deviation in the determination of maleic and fumaric acids at the in situ renewed graphite electrode was 3–6%, and the detection limits for both acids were 0.4 mg/L. The deaeration of the solutions is not needed before the determination, which increases the rapidity of the method.     

Phospholipid and fatty acid composition of Echinodermata. I. ClassOphiuroidea

The phospholipid compositions of five species of marine ophiuroids belonging to the classOphiuroidea have been investigated. It has been shown that the phosphatidylethanolamines contain almost solely ether bonds in the first position of the glycerophospholipids. The amount of the plasmalogen form in the phosphatidylethanolamines averages 89.8% (82.3–96.2%) and the amount of the alkyl form 9.8% (3.8–17.7%). The compositions of the fatty acids, fatty aldehydes, and alkyl ethers in the two main classes of phospholipids — phosphatidylethanolamine and phosphatidylcholine — have been studied. The main acids found were eicosatetraenoic and eicosapentaenoic, the total amount of which was 53%. It has been shown that the ophiuroids can be used as promising objects for the investigation of the metabolism of alkoxylipids and for their preparative isolation.Volga Basin Ecological Institute of the USSR Academy of Sciences, Tol'yatti. Translated from Khimya Prirodnykh Soedinenii, No. 5, pp. 547–551, September–October, 1986.     

Photometrische Bestimmung von Benzylhydrazin und Phenelzin

Zusammenfassung Glutacondialdehyd, hergestellt aus Pyridylpyridiniumdichlorid und Natronlauge, reagiert, wenn er im Überschuß vorliegt, in saurer Lösung mit den Monoaminoxydasehemmern Benzylhydrazin und Phenelzin unter Bildung roter Kondensationsprodukte. Diese Farbreaktion bildet die Grundlage der photometrischen Bestimmungsverfahren, bei denen 0,6–100 nMol/ml der Hydrazinderivate bestimmt werden können. Bei 2 nMol/ml betragen die Variationskoeffizienten 3,2 Rel-% für Benzylhydrazin und 5,2 Rel-% für Phenelzin.

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Photometric determination of benzylhydrazine and phenelzine

Benzylhydraine and phenelzine both of which are inhibitors of monoaminoxidase reactions form red condensation products in their reaction with glutacondialdehyde. The latter compound which was prepared from pyridylpyridinium dichloride and sodium hydroxide has to be in excess concentration. This colour reaction is used in a photometric method to determine 0.6 to 100 nmole/ml of the hydrazine derivatives. The variation coefficients at 2 nmole/ml are 3.2 and 5.2% rel. for benzylhydrazine and phenelzine, respectively.

     

Triflylpyridinium Enables Rapid and Scalable Controlled Reduction of Carboxylic Acids to Aldehydes using Pinacolborane

Building up new and efficient methods for the controlled conversion of carboxylic acids to aldehydes is important. Herein, we report a rapid, modular and scalable method for the conversion of carboxylic acids to aldehydes using pinacolborane at ambient temperature, in which a triflylpyridinium reagent is used. The conversion of carboxylic acid to intermediate acylpyridinium by triflylpyridinium is new. A binary pyridine-coordinated boronium complex is generated after reduction. The unprecedented reduction of the acylpyridinium by HBpin opens up a practically direct synthesis of aldehydes from carboxylic acids. Theoretical studies indicate that the reduction of acylpyridinium requires a lower activation free energy than that of the product aldehyde. The synthetic advantage of this protocol is further highlighted by the scalable synthesis of aldehyde via continuous flow process. Configuration retention for chiral acids are presented in those syntheses.