Complex formation in concentrated sulfuric acid between boric acid and quinalizarin or alizarin

The complex formation in concentrated sulfuric acid between boric acid and quinalizarin (1,2,5,8-tetrahydroxyanthraquinone) or alizarin (1,2-dihydroxyanthraquinone) was studied by spectrophotometry. Both systems contained only one species, viz. a complex between one boric acid and one hydroxyanthraquinone molecules. The reactions of boric acid with hydroxyanthraquinones are discussed and compared with the reaction of boric acid with 1,1'-dianthrimide.     

Complex formation in concentrated sulfuric acid between selenium(iv) and 1,1'-dianthrimide

The complex formation in concentrated sulfuric acid between selenium(IV) and 1,1'-dianthrimide (Di) was studied by spectrophotometry, infrared spectroscopy and chemical analysis. The system was found to contain two species, a Se₂Di complex and aselenium-1,2,7,8-diphthaloylcarbazole complex. The primary complex reaction was assumed to be the formation of the Se₂Di compound; unter certain experimental conditions one selenium atom is split off, resulting in the irreversible formation of a carbazole bond. The selenium-1,2,7,8-diphthaloylcarbazole was prepared in the solid state.     

Complex formation in concentrated sulfuric acid between 1,1'-dianthrimide and germanium(IV) or tellurium(IV)

The complex formation in concentrated sulfuric acid between I,I'-dianthrimide (Di) and germanium or tellurium (IV) was studied by spectrophotometry. The systems contained only one species, GeDi or TeDi; the stability constants in 93.2% sulfuric acid were calculated to be 221 and 228, respectively.     

An investigation of the applicability of 2,2'-dianthrimide in spectrophotometry: The determination of selenium(IV)

2,2'-Dianthrimide was studied as an analytical reagent and compared with the properties of 1,1'-dianthrimide. While 1,1'-dianthrimide reacts with B, Ge, Se and Te, 2,2'-dianthrimide was found to react only with selenium(IV).A straight line calibration curve is obtained up to 50 μg of selenium under the optimum conditions but the value of 2,2'-dianthrimide as a reagent for selenium(IV) is reduced by the high absorption of the reagent itself.     

A qualitative and quantitative color reaction for pyridoxal with sulfuric acid

The carbonyl-phenol-acid reaction system yields color reactions with phenols, carbonyl compounds (aldehydes and ketones), and inorganic acids. 'I'o test for one of the components of this reaction system, the remaining two components constitute the specific reagents.The four related compounds, pyridoxine, pyridoxamine, pyridoxal, and pyridoxic acid each possess a phenolic hydroxyl. Pyridoxal possesses an aldehyde group in addition to the phenolic hydroxyl. Pyridoxal yields an intense yellow color on treatment with concentrated sulfuric acid. Pyridoxine, pyridoxamine and pyridoxic acid prove not to be chromogenic on treatment with concentrated sulfuric acid. Pyridoxal can therefore be differentiated by means of the sulfuric acid reaction from the other three compounds related to vitamin B₆.The colored product obtained by the interaction of pyridoxa1 and concentrated sulfuric acid yields a characteristic absorption spectrum and follows the Beer-Lambert law in the concentrations of pyridoxal tested (l0—100 μg).     

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.

     

Kinetics and Substrate Selectivity of the Oxidation of Saturated Hydrocarbons by Adamantyl Cations in Sulfuric Acid

It was shown that at 70 °C sulfuric acid ([H₂SO₄] > 85 wt.%) solutions of 1-hydroxyadamantane and the solutions obtained in the reaction of adamantane with concentrated sulfuric acid oxidize saturated hydrocarbons (RH). Data on the kinetics, selectivity, kinetic isotope effect, and the effect of the acidity of the medium on the oxidation rate of RH indicate cleavage of the C—H bond in the substrate at the rate-determining stage and the direct participation of adamantyl carbocations.     

Selective dimerization of α-methylstyrene catalyzed by a solid acid

A novel solid acid prepared from concentrated sulfuric, boric and phosphoric acid is a highly selective catalyst for the dimerization of α-methylstyrene at room temperature to generate 4-methyl-2,4-diphenyl-1-pentene.     

Chemical properties of ylidene derivatives of azines. 4. Structures of the products of protonation and transformation of dihydroazinylidenecyanoacetic esters in concentrated sulfuric acid

It was demonstrated by UV and ¹³C NMR spectroscopy that in concentrated sulfuric acid ylidene derivatives of dihydropyridine (Ia) and dihydropyridazine (IIa) have aromatic structures Ib and IIb, while derivatives of dihydropyrimidines IIIa and IVa, dihydropyrazine Va, and dihydro-s-triazine VIa retain ylidene structures IIIb–VIb, respectively, which determines their greater stability in these solutions. When solutions of Ib–VIb in 95% H₂SO₄ were allowed to stand, they were converted to the corresponding azinylmalonic ester monoamides or azinylacetamides, depending on the reaction temperature.See [1] for communication 3.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 960–966, July, 1990.     

Oxidation of aliphatic alcohols by a system containing Na2S2O8 and a metal chloride

Conclusions The oxidation of primary aliphatic alcohols by the Na₂S₂O₈-alkali metal chloride system in water in the presence of sulfuric acid gives 1,1-dialkoxy-2-chloroalkanes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1932–1934, August, 1988.     

Spectrophotometric determination of formaldehyde with chromotropic acid in phosphoric acid medium assisted by microwave oven

In the present study, a spectrophotometric method for the determination of formaldehyde by using chromotropic acid was devised, in which the use of potentially hazardous and corrosive concentrated sulfuric acid was eliminated and advantageously replaced by a mixture of H₃PO₄ and H₂O₂. The reaction between formaldehyde and chromotropic acid (CA) in a concentrated phosphoric acid medium was accelerate by irradiating the mixture with microwave energy for 35 s (1100 W), producing a violet-red compound (λ_max=570 nm). Beer's Law is obeyed in a concentration range of 0.8-4.8 mg l⁻¹ of formaldehyde with a good correlation coefficient (r=0.9968). The proposed method was applied in the analysis of formaldehyde in commercial disinfectants. Recoveries were within 98.0-100.4%, with standard deviations ranging from 0.03 to 0.13%.     

Dipotassium maleate with boric acid

In the title compound, poly[(μ₃‐boric acid)‐μ₄‐maleato‐dipotassium], [K₂(C₄H₂O₄){B(OH)₃}]_n, there are two independent K⁺ cations, one bonded to seven O atoms (three from boric acid and four from maleate), and the other eight‐coordinate via three boric acid and four maleate O atoms and a weak η¹‐type coordination to the C=C bond of the maleate central C atoms. Hydrogen bonding links the boric acid ligands and maleate dianions, completing the packing structure.     

Spectrophotomftric determination of germanium with 1.1'-dianthrimide

In conc. sulfuric acid a coloured complex is formed between germanium and 1.1'-dianthrimide, which has an absorption maximum at 660 mμ, and can be used for the spectrophotometric determination of germanium. The method is applicable at concentrations up to at least 6 mg Ge per 100 ml. Among the more common ions serious interference is caused by boron and fluoride. Thc interference from fluoride is probably due to attack on the glass and release of boron.     

Acidity function of concentrated solutions of 12-tungstophosphoric acid

Conclusions The authors have measured the Hammett acidity functions H₀ of concentrated solutions of H₃PW₁₂O₄₀ in water, aqueous dioxane, and acetic acid. In these solvents the acidity of H₃PW₁₂O₄₀ is higher than those of sulfuric and hydrochloric acids.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 492–493, March, 1982.     

Investigation of the electrochemical behaviour of lead dioxide in aqueous sulfuric acid solutions by using the in situ EQCM technique

The charge-discharge characteristics and the aging mechanism of PbO₂ layers in contact with sulfuric acid solutions of different concentrations (1.5–5.0 M) were studied by using combined cyclic voltammetry and electrochemical quartz crystal microbalance (EQCM) techniques. For this purpose, thick lead dioxide layers were electrodeposited on gold substrate from aqueous solutions of Pb(NO₃)₂ dissolved in nitric acid. Based on the electrochemical and the mass change responses, it was found that in more concentrated solutions of H₂SO₄, the main reduction reaction was the transformation of lead dioxide to lead sulfate. However, in less concentrated sulfuric acid media, the transformation of lead dioxide to lead(II) ion became the main reaction. These Pb²⁺ ions transformed into lead sulfate crystals later by a chemical reaction. Because the electrochemical oxidation of lead sulfate is less favourable in sulfuric acid medium of higher concentrations, thus, PbO₂ layers cannot be tested by continuous cyclization, which is necessary to study their aging parameters. Therefore, a delay step before each cyclic voltammogram was applied while the non-conductive lead sulfate dissolves or alternatively, by applying a pre-oxidation step prior to each cyclic voltammetry experiment to produce electrochemically significant amount of lead dioxide which can be reduced during the following negative potential sweep.

     

Novel transformations of nitraminodiol diacetates

A novel scission reaction of nitraminodiol diacetates of the formula AcO[CH₂N(NO₂) _x CH₂OAc (x = 1–4) in concentrated sulfuric acid to form formaldehyde, nitramide, and 2-nitro-2-azapropane-1,3-diol disulfate was found.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya. No. 3, pp 761–762, March, 1996.     

Water Mediated Domino Knoevenagel‐Michael‐cyclocondensation Reaction of Malononitrile,Various Aldehydes and Barbituric Acid Derivatives Using Boric Acid Aqueous Solution System Compared with Nano‐titania Sulfuric Acid

Nano‐titania sulfuric acid (TSA) and boric acid [B(OH)₃] were efficiently utilized for domino Knoevenagel‐Michael‐cyclocondensation reaction of malononitrile, various aldehydes and barbituric acid derivatives to synthesis of pyrano[2,3‐d]pyrimidine diones. It is interesting that in boric acid aqueous solution system, H⁺ which abstracted from water by the interaction with B(OH)₃, efficiently catalyzed the reaction.     

Manganese Complexes with Octaphenyltetraazaporphine: Acid–Base Interactions and Kinetic Stability in Proton-Donor Solvents

Complexes of manganese(III) and manganese(V) with octaphenyltetraazaporphine (H₂OPTAP) were synthesized. Acid–base interactions of these complexes in the CH₂Cl₂–CF₃COOH system and kinetics of their dissociation in concentrated sulfuric acid, as well as kinetics of octaphenyltetraazaporphine destruction in sulfuric acid solutions were studied by spectrophotometric methods. Acid–base interactions in CH₂Cl₂–CF₃COOH were shown to involve two macrocyclic meso-nitrogen atoms in succession. Concentration stability constants of the acid forms obtained pK ₁ = 0.29 ± 0.01 and pK ₂ = –0.62 ± 0.08 for (chlorine)manganese(III)octaphenyltetraazaporphine ((Cl)MnOPTAP); pK ₁ = 0.99 ± 0.02 and pK ₂ = – 0.70 ± 0.03 for (nitrido)manganese(V)octaphenyltetraazaporphine ((N)MnOPTAP). The rate of dissociation of the complexes in 94–98% H₂SO₄ does not depend on the acid concentration. The manganese(V) complex is three times as stable as the manganese(III) complex.     

Sulfuric acid breakdown of fluorite in the presence of silica

We study the reaction of CaF₂ with concentrated sulfuric acid in the presence of silica at 120 and 140°C using fluorite mineral, fluorite concentrate, and mica-fluorite ore samples. When steam is fed to the reaction mixture, fluorosilicic acid is formed and then distilled off, materially influencing the fluoride ion recovery. Addition of quartz makes the reaction to proceed in the kinetic area and increases the fluoride ion recovery, while the presence of mica-bound SiO₂ displaces the reaction to the diffusion area and decreases the fluoride ion recovery. We have found that rare alkali metals are concentrated as hexafluorosilicates in the insoluble residue during the sulfuric acid breakdown of fluorite in the presence of SiO₂.     

Carbon-13 kinetic isotope effects in the decarbonylations of lactic acid containing13C at the natural abundance level

The¹³C kinetic isotope fractionation in the decarbonylation of lactic acid of natural isotopic composition by sulfuric acid has been studied in the temperature range of 20–80°C. The¹³C₍₁₎ isotope separation in the decarbonylation of lactic acid by concentrated sulfuric acid depends strongly on the temperature above 40°C. Below this temperature the¹³C isotope effect in the decarbonylation of lactic acid by concentrated sulfuric acid is normal similarly as has been found inthe decarbonylation of lactic [1-¹⁴C] acid. The experimental values of k(¹²C)/k(¹³C) ratios of isotopic rate constants for¹²C and¹³C are close to, but slightly higher than theoretical¹³C-kinetic isotope effects calculated (neglecting tunneling) under the asumption that the C₍₁₎-OH bond is broken in the rate-controlling step of the dehydration reaction. Dilution of concentrated sulfuric acid with water up to 1.4 molar (H₂O)/(H₂SO₄) ratio caused the increase of the¹³C isotope fractionation from 1.0273 found in concentrated sulfuric acid at 80.5°C to 1.0536±0.0008 (at 80.6°C). A discussion of the abnormally high temperature dependence of¹⁴C and¹³C isotope fractionation in this reaction and the discussion of the problem of relative¹⁴C/¹³C kinetic isotope effects is given.