2-methylimidazole as a reagent for the photometric determination of maleic anhydride

The formation of molecular complexes of maleic anhydride with some substituted imidazoles in acetonitrile, dimethylformamide, and dimethyl sulfoxide was studied. The selection of 2-methylimidazole as a reagent for the photometric determination of maleic anhydride in the dimethyl sulfoxide medium was substantiated using kinetic and spectrometric techniques.     

Maleic anhydride as a reagent for the determination of hydroxyl groups in organic compounds

The reaction of esterification by maleic anhydride in methyl ethyl ketone in the presence of triethylamine is proposed for the determination of alcohol hydroxyl groups. The equivalent amount of maleic anhydride that entered into the reaction is determined spectrophotometrically by the reaction with 2-methylimidazole. In the determination of hydroxyl groups in epoxy-dian resins, maleic anhydride is determined by the potentiometric titration with alkali after hydrolysis with water by the first potential jump.     

Room temperature-stable electride as a synthetic organic reagent: application to pinacol coupling reaction in aqueous media

Room temperature-stable inorganic electride [Ca(24)Al(28)O(68)](4+)4e(-) was employed for a pinacol coupling reaction in aqueous media. Ca-Al-O gel formed by the destruction of the crystal structure of an electride by water media played a key role in transferring the electron to electrophilic aldehydes. Aromatic aldehydes reacted smoothly with moderate to high yields.     

Resorcinol as a reagent for zinc

The use of the zinc-ion-catalyzed autoxidation or hydrogen peroxide oxidation of resorcinol (1,3-dihydroxybenzene) to determine zinc concentration has been examined. The nature of the reaction products involved, the conditions of reagent concentration, pH, and reaction time have been specified. The procedure will yield results with a relative average deviation of 10% over the concentration range of 0.9 ppm to approximately 8 ppm. It is an inexpensive and convenient reagent and procedure.     

Thenoyltrifluoroacetone as a reagent for cobalt

Summary An indirect method is proposed for the determination of cobalt (II) with 2-thenoyltrifluoroacetone at the milligram level. The orange cobalt-TTA chelate can be quantitatively precipitated over the p_H range 4.0–8.0. It is dissolved in acid and estimated as cobalt sulphate. Cobalt(II) can be estimated in presence of silver, mercury(II), strontium, iron(III), chromium (III), thorium, zirconium, uranium, citrate and tartrate. The method is reproducible to within ±1 per cent.     

"GaI": a versatile reagent for the synthetic chemist

The current renaissance in main group chemistry has been fuelled by the remarkable array of fundamentally interesting yet synthetically applicable low oxidation state p-block compounds that have appeared over the last decade. Their syntheses generally require the ready availability of low oxidation state element halide precursors. In the case of gallium this is provided by the simple to prepare reagent, "GaI", which since it was first reported in 1990, has been utilised in areas as varied as organic synthesis and gallium cluster construction. This article tracks the history of this extraordinary material and highlights its synthetic diversity; hopefully allowing the reader to envisage its application to aspects of their own research fields.     

A new reagent pair sodium percarbonateacetic anhydride for epoxidation of olefins

A new convenient method for epoxidation of olefins by sodium percarbonate — acetic anhydride is reported. It is found that the epoxides in 60–80% yields can be obtained in 18–24 h without ultrasonication. However, higher yields (some nearly quantitative) can be reached only within 1–3 h under ultrasonication. A comparison between the ultrasonicated epoxidations by use of sodium percarbonate and sodium perborate is also made. The experimental results have revealed that ultrasonication plays a main role in accelerating the interaction of both sodium percarbonate and sodium perborate with acetic anhydride, but it does not alter the mechanism of these two epoxidations.     

Morin as a spectrophotometric reagent for gold

A reaction of morin with gold(III) in a hydrochloric acid medium has been studied. A redox reaction occurring in the examined system has been identified. The oxidized form of morin (λ_max at 291 nm), being the product of the reaction, has been used as the basis of the spectrophotometric method for the determination of gold. Gold can be determined in the concentration range of 0.2–12 μg mL⁻¹ (RSD in the range of 0.89–2.38%). The molar absorptivity at 291 nm is equal to 2.02 × 10⁴ L mol⁻¹. cm⁻¹. The developed method was applied to the determination of gold (0.04%) in a cosmetic cream. Published in Russian in Zhurnal Analiticheskoi Khimii, 2006, Vol. 61, No. 2. pp. 129–133. The text was submitted by the authors in English.     

Thiodiglycolic acid as a reagent for zirconium

Thiodiglycolic acid is shown to be a suitable precipitating reagent for zirconium. The analysis is completed by igniting the precipitate and weighing the ZrO₂. Several metal ions do not interfere. Interference due to cerium(IV) is avoided by reducing it initially to cerium(III). Estimation of zirconium can be carried out in presence of thorium. The composition of the Complex is slightly variable but corresponds to zirconyl thiodiglycolate: O =

     

Calmagite as a spectrophotometric reagent for aluminium

Calmagite is proposed as a sensitive spectrophotometric reagent for aluminium, (570mmu) = 42000. After aqueous phase reaction at pH 8.6, the metal-reagent complex is extracted into chloroform by formation of an ion-association complex with a quaternary ammonium salt. The method is free from interference by common anions, and cationic interferences may be eliminated by the use of cyanide and EDTA as masking agents.     

Equilibrated radical polymerization of acrylic propionic anhydride as a mono-ene counterpart of acrylic anhydride

Radical polymerization of acrylic propionic anhydride (APA) as a mono-ene counterpart of acrylic anhydride (AA) was investigated in order to obtain supporting evidence for a previously proposed mechanism based on polymerization equilibrium for the cyclopolymerization of AA. The deviation from first-order dependence of the rate of polymerization R_p on monomer concentration was enhanced by a decrease in monomer concentration. The Arrhenius plot of lnR_p vs. 1/T was clearly curved in a highly dilute system. These results suggest increased significance of the depropagation reaction equilibrated with propagation under polymerization conditions favorable to five-membered ring formation in cyclopolymerization of AA. Under these conditions, the disproportionation reaction of APA became important and the liberated AA was incorporated into the polymer chain through copolymerization with APA, resulting in poly(APA-co-AA) having five-membered anhydride units.     

Use of biguanide sulphate as a reagent

Summary The paper introduces biguanide acid sulphate, C₂N₅H₇ · H₂SO₄ · 1,5H₂O, as a primary standard acidimetric reagent. The reagent has several advantages over some of the primary standard acidimetric reagents commonly used. It is economic.     

Acetic anhydride at 100 K: the first crystal structure determination

Acetic anhydride (ethanoic anhydride), (CH₃CO)₂O, is a widely used acetylation reagent in organic synthesis. The crystal and molecular structure, as determined by single‐crystal X‐ray analysis at 100 K, is reported for the first time. A crystal of the title compound (m.p. 200 K) suitable for X‐ray diffraction was grown from the melt at low temperature. The title compound crystallizes in the orthorhombic space group Pbcn, with Z = 4. In the crystal, the molecule adopts an exact C₂‐symmetric conformation about a crystallographic twofold axis. The molecules are densely packed. Two of the methyl H atoms form short intermolecular contacts to a neighbouring carbonyl O atom, which can be viewed as weak hydrogen bonds.     

Monohalomethyllithium XCH2Li: stabilization of a potential synthetic reagent

The preparation of monohalomethyllithium XCH₂Li is achieved by Bromine-lithium exchange from the corresponding Bromohalomethane in the presence of $\text{one equivalent of lithium bromide}$ at ?110° in THF-Ether-Pentane solutions. This reagent, on coupling with various carbonyl compounds leads to halohydrins, epoxides and α-halomethyl ketones with high yields.     

A facile and efficient synthetic method for 4-phenylethynylphthalic anhydride

A novel approach to the synthesis of 4-phenylethynylphthalic anhydride has been described.The target compound was synthesized by Pd/Cu catalyzed Sonogashira coupling reaction between phenylacetylene and 4-bromophthalic acid which was for the first time employed as start material,followed by dehydration of 4-phenylethynylphthalic acid.Compared with traditional synthetic routes,this method provides several advantages such as readily available raw materials,convenient manipulation and high yield.The product...     

Sodium alizarin-3-sulphonate as a chromophoric reagent

Summary A method for the colorimetric determination of hexavalent tungsten with Alizarin Red S has been described. The composition of the coloured chelate is MKe₂ and the wave length of maximum absorption is 470 nm. The colour reaction is almost instantaneous. The coloured complex conforms to Beer's Law over tungsten concentration of 0.37 to 13.3 ppm. The suitable p_H for the measurement is 3.5 to 5.8 and temperature has no effect on the intensity of the colour. The sensitivity is 0.037 g/cm² (Sandell) and 0.37 g/cm² (practical) based on an absorption of 0.01 unit. The interference of added foreign ions has also been investigated and most of the common ions are found to interfere and should, therefore, be removed before determination of tungsten is made.

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Zusammenfassung Es wird eine Methode zur colorimetrischen Bestimmung von Wolfram(VI) mit Alizarinrot S beschrieben. Die Zusammensetzung des Farbkomplexes ist MeAliz₂, das Absorptionsmaximum liegt bei 470 nm. Die Farbreaktion verläuft fast augenblicklich und gehorcht dem Beer'schen Gesetz im Bereich von 0,37–13,3 ppm Wolfram. Der günstigste p_H-Bereich liegt zwischen 3,5 und 5,8. Die Temperatur ist ohne Einfluß auf die Farbintensität. Die Empfindlichkeit beträgt 0,037 g/cm² (Sandell) bzw. praktisch 0,37 g/cm² (Absorption 0,01 Einheiten). Da die meisten Fremdionen stören, müssen sie vor der Bestimmung abgetrennt werden.

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Part I: Banerji, S. K., and A. K. Dey: Z. analyt. Chem. 179, 30 (1961).