The direct micro determination of oxygen in organic material

A procedure is described in which interferences caused by hydrogen and sulphur are eliminated. These occur when petroleum hydrocarbons or sulphur containing materials are analysed. Copper oxide, in conjunction with the gravimetric determination of carbon dioxide, has been found preferable to the iodine pentoxide procedure. The replacement of iodine pentoxide by copper oxide has also simplified the maintenance of the apparatus without any loss of applicability to organic compounds in general. Activated copper is used to absorb sulphur compounds. Details of the modified procedure are included.     

Four-component benzyne coupling reactions: a concise total synthesis of dehydroaltenuene B

A four-component coupling reaction of 3,5-dimethoxybenzyne with 2-methyl-2-cyclohexenylmagnesium chloride, carbon dioxide, and iodine was utilized as a key step in the first total synthesis of dehydroaltenuene B.     

Simple spectrophotometric and titrimetric methods for the determination of sulfur dioxide.

The proposed work describes a simple spectrophotmetric as well as a titrimetric method to determine sulfur dioxide. The spectrophotometric method is based on a redox reaction between sulfur dioxide and iodine monochloride obtained from iodine with chloramine-T in acetic acid. The reagent iodine monochloride oxidizes sulfur dioxide to sulfate, thereby reducing itself to iodine. Thus liberated iodine will also oxidize sulfur dioxide and reduce itself to iodide. The obtained iodide is expected to combine with iodine to form a brown-colored homoatomictriiodide anion (460 nm), which forms an ion-pair with the sulfonamide cation, providing exceptional color stability to the system under an acidic condition, and is quantitatively relatd to sulfur dioxide. The system obeys Beer's law in the range 5 - 100 microg of sulfur dioxide in a final volume of 10 ml. The molar absorptivity is 5.03 x 10(3) l mol(-1)cm(-1), with a relative standard deviation of 3.2% for 50 microg of sulfur dioxide (n = 10). In the titrimetric method, the reagent iodine monochloride was reduced with potassium iodide (10%) to iodine, which oxidized sulfur dioxide to sulfate, and excess iodine was determined with a thiosulfate solution. The volume difference of thiosulfate with the reagent and with the sulfur dioxide determined the sulfur dioxide. Reproducible and accurate results were obtained in the range of 0.1 - 1.5 mg of sulfur dioxide with a relative standard deviation of 1.2% for 0.8 mg of sulfur dioxide (n = 10).     

Deprotonation and regioselective addition of 2H-pyrazolo[3,4-c]quinolines to electrophiles

The deprotonation and regioselective reaction of 2H-pyrazolo[3,4-c]quinolines with a variety of electrophiles is described. Electrophiles include benzaldehyde, DMF, carbon dioxide, and iodine. This method provides a direct route to a class of pharmacologically interesting compounds.     

Studies in oxidation-reduction reactions: Oxidation with chloramine-b indirect determinations

Chloramine-B has been used as an oxidizing agent in hydrochloric acid medium for the indirect volumetric estimations of hydrogen peroxide, lead dioxide, manganese dioxide, selenium dioxide, sodium formate, sodium sulphide, sodium metavanadate, potassium iodate and copper sulphate using iodine monochloride as a catalyst and pre-oxidiser. Chloroform is used as an indicator. It is coloured pink owing to the liberation of iodine during the titration and becomes light pale yellow at the end-point because of the formation of iodine monochloride.     

Sodium meta-vanadate as volumetric reagent : Iodine monochloride method (Indirect determinatios)

Sodium meta-vanadate has been used as an oxidizing agent in hydrochloric acid medium for the indirect volumetric determination of hydrogen peroxide, lead dioxide, manganese dioxide, selenium dioxide, potassium persulphate, copper sulphate, sodium formate and sodium sulphide using iodine monochloride as a catalyst, pre-oxidizer and an indicator. Chloroform is coloured pink owing to the liberation of iodine during the titration and becomes light pale yellow at the end-point owing to the formation of iodine monochloride.     

Separation with Supercritical Gases: Practical Applications

Extraction with supercritical gases combines, to a certain extent, the characteristics of both distillation and extraction; the term “destraction” is therefore proposed for this method of separation. The principles of the method are illustrated in this article by a series of color photographs comparing extraction and destraction. Of the practical uses of this new method may be mentioned the separation of cod-liver oil into 50 fractions, each differing in saponification value and iodine number, by means of supercritical ethane and, in particular, the decaffeination of raw coffee with supercritical carbon dioxide.     

Neue Methode zur gleichzeitigen Mikrobestimmung von Kohlenstoff und Jod in organischen Substanzen

Zusammenfassung Eine neue Methode zur gleichzeitigen Mikrobestimmung von Kohlenstoff und Jod in organischen Verbindungen wird beschrieben. Sie beruht auf der Verbrennung der Substanz im Sauerstoffstrom in Gegenwart einer Bariumchromatfüllung bei 600° C und auf der Titration des Jods und des Kohlendioxids.Das Jod wird zuerst in einem mit Trockeneis gekühlten Rohr abgeschieden und dann mit Natronlauge gelöst und nachLeipert maßanalytisch bestimmt, während das Kohlendioxid in Dimethylformamid in Gegenwart von Monoäthanolamin absorbiert und mit Tetra-n-butylammoniumhydroxid automatisch titriert wird. Die Dauer der Bestimmung beträgt 18 bis 20 Minuten. Die Resultate sind für beide Elemente sehr genau und reproduzierbar.

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Summary A new method is described for the simultaneous microdetermination of carbon and iodine in organic materials. It is based on combustion of the sample in a stream of oxygen in the presence of a barium chromate filling at 600° C and the titration of the iodine and the carbon dioxide. The iodine is first precipitated in a tube cooled with dry ice and then dissolved in caustic soda and determined titrimetrically afterLeipert. The carbon dioxide is absorbed in dimethylforrnamide in the presence of monoethanolamine and titrated automatically with tetra-n-butylammonium hydroxide. The determination occupies about 18–20 minutes. The results for both elements are very precise and reproducible.

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Herrn Prof. Dr.Hans Lieb zum 80. Geburtstag gewidmet.     

Volumetric studies in oxidation-reduction reactions: Oxidation with chloramine-t. indirect determinations

Chloramine-T has been used as an oxidizing agent in hydrochloric acid medium for the indirect volumetric determination of hydrogen peroxide, lead dioxide, selenium dioxide, sodium formate, potassium meta-periodate, potassium permanganate and potassium dichromate using iodine monochloride as a catalyst, prcoxidizer and an indicator. Chloroform is coloured pink owing to the liberation of iodine during the titration and becomes very pale yellow at the end-point because of the formation of iodine monochloride.     

Tandem radical decarboxylation-oxidation of amino acids: A mild and efficient method for the generation of N-acyliminium ions and their nucleophilic trapping

A convenient methodology for the synthesis of 2-substituted pyrrolidines from alpha-amino acids is described. A number of cyclic and acyclic alpha-amino acid derivatives have been prepared in order to test the scope and diastereoselectivity of this method. These substrates were treated with iodosylbenzene or (diacetoxyiodo)benzene (DIB) and iodine in order to generate the corresponding carboxyl radical, which evolves by loss of carbon dioxide to produce a carbon radical which in turn undergoes oxidation to an N-acyliminium ion. This postulated intermediate could be trapped inter- or intramolecularly by oxygen, nitrogen and carbon nucleophiles. In the case of carbon nucleophiles, a Lewis acid is required for the concomitant carbon-carbon bond formation. High yields and modest diastereoselectivities were obtained. The present methodology was applied to the synthesis of omega-amino aldehydes or hemiaminals 8-14, 2-aminopyrrolidine derivative 15, aminolactone derivative 16, and azasugar analogues 17 and 18. When carbon nucleophiles were used, alkaloid precursors such as 2-allyl- or 2-alkylpyrrolidines 19-23 and 25 were obtained.     

The direct determination of oxygen in organic compounds : Investigation of some sources of error in the schütze-unterzaucher carbon reduction method

Experience with the Schütze carbon reduction method in the UNTERZAUCHER modification showed (1) an inconveniently high blank value and (2) the necessity of an extra correction in the analysis of substances low in oxygen content (e.g., hydrocarbon oils). These drawbacks could be eliminated by changing the volumetric iodine finish to a gravimetric carbon dioxide one and intensifying the purification of the transport gas. Although a blank remains, it is sufficiently small not to interfere with routine determinations; its influence on the results varies from 0.2 to 0.04 per cent of oxygen when sample intakes from 35 to 200 mg are employed. Some more factors governing the accuracy of the method are discussed.     

Determination of chlorine dioxide in water by gas chromatography-mass spectrometry

A sensitive gas chromatographic method has been established for the determination of chlorine dioxide in water. With weak basic conditions (pH 9.0), chlorine dioxide reacts with iodide to form iodine, which reacts with 2,6-dialkylphenol to form 4-iodo-2,6-dialkylphenol. The volatile organic derivative was extracted with ethyl acetate, and then measured by gas chromatography-mass spectrometry (GC-MS). The reaction of the active proton of 2,6-dialkylphenols (2,6-dimethylphenol, 2,6-di-isopropylphenol and 2,6-di-tert-butylphenol) with iodine was tested, and compared to each other in terms of reactivity and stability of the derivatives. 2,6-dimethylphenol showed rapid reaction with iodine, and its derivative was stable for 2 weeks. The detection limit of chlorine dioxide in water was about 1.0 ng/mL, and the calibration curve showed good linearity with r2 = 0.998. The existent concentration of chlorine dioxide in water was calculated from multiplying the concentration calculated from the calibration curve of 4-iodo-2,6-dimethylphenol by 0.544. The method was sensitive, reproducible and simple enough to permit the reliable analysis of chlorine dioxide at the low ng/mL level in water.     

Reaction rates between water and the Karl Fischer reagent

Reaction rates between water and the Karl Fischer reagent have been determined by potentiometric measurement for various compositions of the Karl Fischer reagent. The study has been made with an iodine complex concentration of 0.3-1.2 mM and sulphur dioxide complex at 0.01-0.5M. The concentration of excess of pyridine had no measurable effect on the rate of the main reaction. The reaction was found to be first-order with respect to iodine complex, to sulphur dioxide complex, and to water. The rate constant was (1.2+/-0.2) x 10(3) 1(2). mole(-2). sec(-1). In an ordinary titration it is therefore essential to keep the sulphur dioxide concentration high for the reaction to go to completion within a reasonable time. The extent of side-reactions was found to be independent of the iodine concentration at low concentrations. The side-reactions increased somewhat with increasing sulphur dioxide pyridine concentrations and decreased to about 60% when the temperature was lowered from 24 degrees to 7 degrees.     

Complexes in polymers III: Addition reactions of trans-Ir(PPh3)2(CO)Cl embedded in polystyrene with hydrogen,oxygen, sulfur dioxide,carbon monoxide and gaseous iodine and of (η-C5H5)Ru(η4-1,5-cyclooctadiene)Cl in polystyrene with carbon monoxide

The addition rections of trans-Ir(PPh₃)₂(CO)Cl embedded in films of polystyrene (PS) with hydrogen, oxygen, sulfur dioxide, carbon monoxide and gaseous iodine were monitored by infrared spectroscopy and found to be similar to those occurring in toluene. While the reaction with iodine was rapid at the surface of the film as determined by attenuated-total-reflectance infrared spectroscopy, the reaction was much slower in the body of the film, as shown by transmission infrared spectroscopy. No such difference was observed for oxygen. The complex CpRu(COD)Cl (Cp = η-C₅H₅, COD = 1,5-cyclooctadiene) in PS readily undergoes ligand substitution by carbon monoxide (CO and ¹³CO) to give CpRu(CO)₂Cl and CpRu(¹³CO)₂Cl embedded in PS, respectively.     

Stannometry volumetric determination of iron(iii), vanadate,dichromate, iodate,bromate, ferricyanide ions and iodine

A generally applicable reductive method was elaborated by means of which numerous substances can be determined having oxidation potentials exceeding 0.3 V. The 0.1 N stannous chloride standard solution can be stored for some months, with a very slight decrease in titre, by using an automatic equipment for the supplying with carbon dioxide of the storage flask and burette. The procedure has so far been employed for the determination of ferric-, ferrous-, dichromate-, vanadate-, bromate-, iodate- and ferricyanide ions, furthermore of iodine. The advantage of the method is — in addition to the simplicity of the realization — that in the given ranges the experimental error never exceeds 0.5%, remaining usually under this limit.     

Halogen-Mediated Membrane Transport: An Efficient Strategy for the Enhancement of Cellular Uptake of Synthetic Molecules

The poor uptake of fluorescent probes and therapeutics by mammalian cells is a major concern in biological applications ranging from fluorescence imaging to drug delivery in living cells. Although gaseous molecules such as oxygen and carbon dioxide, hydrophobic substances such as benzene, and small polar but uncharged molecules such as water and ethanol can cross the cell plasma membrane by simple passive diffusion, many synthetic as well as biological molecules require specific membrane transporters and channel proteins that control the traffic of these molecules into and out of the cell. This work reports that the introduction of halogen atoms into a series of fluorescent molecules remarkably enhances their cellular uptake, and that their transport can be increased to more than 95 % by introducing two iodine atoms at appropriate positions. The nature of the fluorophore does not play a major role in the cellular uptake when iodine atoms are present in the molecules, as compounds bearing naphthalimide, coumarin, BODIPY, and pyrene moieties show similar uptakes. Interestingly, the introduction of a maleimide-based fluorophore bearing two hydroxyethylthio moieties allows the molecules to cross the plasma and nuclear membranes, and the presence of iodine atoms further enhances the transport across both membranes. Overall, this study provides a general strategy for enhancing the uptake of organic molecules by mammalian cells.     

重量法测定灰岩中的二氧化碳

采用重量法对灰岩中的二氧化碳进行测定。首先用酸分解试样,在载气作用下,产生的二氧化碳被吸收液完全吸收,最后用重量法间接求出二氧化碳的含量。实验结果准确度高,矿石中的硫不干扰测定,可测定0.1%以上的二氧化碳。不经过复杂的气体净化步骤,操作准确、简单、易行,可用于灰岩中二氧化碳的测定。     

Volumetric method for the estimation of tin(II)

Summary A rapid and easy volumetric method for the estimation of tin(II) has been proposed using copper sulphate solution. The method consists of liberating iodine from an excess of potassium iodide solution by the addition of a known volume of a standard copper sulphate solution and to this, adding a known volume of stannous chloride solution. The remaining iodine in the solution is titrated against a standardized solution of sodium thiosulphate. Carbon dioxide atmosphere is not essential during the titration. However, freshly boiled conductivity water cooled and stored under carbon dioxide atmosphere should be used for making up the solutions.

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Zusammenfassung Zinn(II) kann volumetrisch auf schnelle und einfache Art bestimmt werden, wenn man durch Zugabe einer bekannten Menge Kupfersulfatlösung zu überschüssiger Kaliumjodidlösung Jod in Freiheit setzt, die Zinn(II)-probelösung zugibt und überschüssiges Jod mit Thiosulfatlösung zurücktitriert. Es ist nicht erforderlich, die Titration in C0₂-Atmosphäre durchzuführen, jedoch soll zur Herstellung der Lösungen ausgekochtes und unter CO₂ aufbewahrtes Leitfähigkeitswasser verwendet werden.