Spectrophotometric determination of trace amounts of thallium with 7-(4,5-dimethylthiazolyl-2-azo)-8-hydroxyquinoline-5-sulphonic acid

A new reagent, 7-(4,5-dimethylthiazolyl-2-azo)-8-hydroxyquinoline-5-sulphonic acid, has been examined to evaluate its usefulness as a spectrophotometric reagent for thallium(III). A purple-red complex is formed in aqueous solution at pH 4-5 in the presence of cetylpyridinium chloride and the stoichimetric ratio is 1:2 (Tl:reagent). The apparent stability constant is 1.5 x 10(11). The effect of diverse ions has been studied and a method for determining trace amounts of thallium is proposed.     

Synthesis of 1-Acetamido-2-acetyladamantane

The triple bond of 2-ethynyl-2-adamantanol virtually did not hydrolyze under Kucherov reaction conditions in aqueous ethanol and methanol. In aqueous acetic acid arose a mixture of 2-acetyl-2-adamantanol and its acetate. In good yield the 2-acetyl-2-adamantanol was obtained by Kucherov reaction in aqueous THF. This alcohol with acetonitrile under conditions of Ritter's reaction (catalysis with sulfuric acid) afforded a mixture of 1-acetamido-2-acetyl-, 1-acetamido-4-cis- and 1-acetamido-4-trans-acetyladamantanes in 8:1:1 ratio.     

Studies with dithizone : Part 26. The interaction of thallium(III) with solutions of dithizone in organic solvents

The strong oxidising capacity of thallium(III) dominates its reaction with solutions of dithizone (H₂Dz) in organic solvents. When carbon tetrachloride is used as solvent, the unstable thallium(III) complex Tl(HDz)³ is found in the organic phase but it very quickly disproportionates to the thallium(I) complex [Tl(HDz)], and bis-1,5-diphenylformazan-3-yl-disulphide. This reaction is notably faster in chloroform, in which thallium(I) dithizonate is the first identifiable product. In contact with an acidic aqueous phase, thallium(I) dithizonate is reverted to regenerate dithizone in the organic phase and Tl⁺ ions appear in the aqueous phase. Organic solutions of the disulphide disproportionate spontaneously by first-order kinetics to give an equimolar mixture of dithizone and the mesoionic compound, 2,3-diphenyl-2,3-dihydrotetrazolium-5-thiolate: this change is much slower in carbon tetrachloride than in the more polar chloroform and is catalysed by both Tl⁺ and Tl³⁺. If thallium(III) is present in excess, the mesoionic compound is the principal oxidation product of the dithizone although a dication may also be formed. The mesoionic compound does not react with thallium(I) but forms a water-soluble 2:1 complex with thallium(III); partition of this complex into the organic phase is uninfluenced by chloride ions. Because of the large number of competing reactions, the composition of the reaction mixture at any stage of the reaction between thallium(III) and dithizone depends on the relative concentrations of the components, the order in which they are brought together, the time elapsed after mixing, the pH of the aqueous phase, and the nature of the organic solvent.     

The Reaction of Norbornene with Lead Tetraacetate and Thallium Trinitrate. Preliminary communication

The reaction of norbornene with lead tetraacetate is found to be much more complex than previously reported. In acetic acid and in benzene, the syn-7-norbornenyl, 3-nortricyclyl, and syn and anti-7-acetoxy-exo-2-norbornyl acetates were characterized. In methanol, the isolated products represented most of those expected from the competition of methanol and acetate in the neutralization of the intermediate carbocations. The reaction of norbornene with thallium trinitrate in the above solvents yielded very complex mixtures besides the above mentioned products which were formed in about 50% yield.     

Synthesis of an Isostegane from Matairesinol

In a recent communication,¹ we reported that the inclusion of boron trifluoride etherate in a thallium(III) trifluoroacetate (TTFA)-induced oxidative aryl-benzyl coupling reaction dramatically altered its outcome in that demethylation of a-phenyl methyl ether no longer accompanied the cyclization. A preliminary investigation also revealed that use of the combined reagents improved the yield of the dibenzocyclooctadiene obtained from a non-phenolic aryl-aryl coupling of a 1,4-diaryl substituted butane.²     

Synthesis, Properties, and Crystal Structures of Benzene-1,2-dithiolato Complexes of Thallium(I) and -(III)

The syntheses, molecular structures and properties of homoleptic 1,2-S(2)C(6)H(4) complexes of thallium(I) and thallium(III) with four-coordinated metal centers are described. Anaerobic treatment of TlCl, TlNO(3), or Tl(2)CO(3) with solutions of sodium methanolate and 1,2-(HS)(2)C(6)H(4) in methanol gave after metathesis with [NEt(4)]Br yellow solutions of [NEt(4)](2)[{Tl(1,2-(&mgr;-S)(2)C(6)H(4))}(2)] ([NEt(4)](2)1). Yellow single crystals were obtained from saturated acetone solutions at -10 degrees C and the crystal data for [NEt(4)](2)1 are monoclinic, P2(1)/c, with Z = 2, a = 7.440(1) ?, b = 16.373(3) ?, c = 13.201(2) ?, and beta = 97.08(1) degrees. Complex 1(2)(-)(), the first structurally characterized homoleptic ionic thiolate complex of thallium(I), contains rectangular bipyramidal [TlS(4)Tl] cages with the four sulfur atoms defining the equatorial plane and the two thallium atoms in axial positions. The S(2)C(6)H(4) fragments are almost coplanar with the S(4) plane. In the crystal lattice, nearly linear Tl.Tl chains align along the a-axis (offset ca. 3.0 degrees ) with the ligand planes parallel to the bc-plane. Within and between dimers short Tl.Tl distances are observed (Tl.Tl' within a dimeric unit, 3.5116(4) ?; Tl.Tl between dimeric units, 3.9371(3) ?) with the distance between dimeric units being the shortest contact between anions-Tl.S distances between dimeric units are longer than 5.8 ?. Aerobic treatment of TlCl, TlNO(3), or Tl(2)CO(3) with solutions of sodium methanolate and 1,2-(HS)(2)C(6)H(4) in methanol and metathesis with [NEt(4)]Br led to [NEt(4)][Tl(1,2-S(2)C(6)H(4))(2)] ([NEt(4)]2). Yellow single crystals were obtained from saturated acetone solutions at 0 degrees C and the crystal data for [NEt(4)]2 are orthorhombic, Pnn2, with Z = 2, a = 11.449(2) ?, b = 10.060(2) ?, c = 9.950(2) ?. Complex 2(-) is the first homoleptic four-coordinate thiolate of thallium(III) and contains the unusually short Tl-S distance of 2.469(4) ?. In solution, ion pairing results in chemical and magnetic inequivalence of the S(2)C(6)H(4) ligands. Although both preparations employ the reaction of thallium(I) salts with 1,2-(NaS)(2)C(6)H(4) in a 1:2 stoichiometry, complex 1(2)(-) is probably not an intermediate to the formation of 2(-). Exposing anaerobically prepared solutions of 1(2)(-) to air results in a series of color changes in the solution over a 20 min period; however, 2(-) could not be observed by NMR spectroscopy.     

Synthons for biologically active compounds on the basis of naphthalene ozonolysis products

Ozonolysis of naphthalene in aqueous methanol, followed by the reduction of peroxy compounds thus formed with potassium iodide in the presence of acetic acid, gave 3-methoxy-2-benzofuran-1(3H)-one. In the absence of water, the product was methyl o-formylbenzoate. The latter was used as a synthon for the preparation of aromatic analogs of (2E)-2,6-dimethyloct-2-ene-1,8-diol ethers which are effective juvenoids.     

稀土噻吩甲酰三氟丙酮喹啉螯合物的振动光谱

本文测定了系列稀土螯合物(TTA)_4LnQH的振动光谱, 讨论了螯合物的结构, 低波数谱带和Ln-O振动。     

Development of new isothiocyanate-based chiral derivatizing agent for amino acids

Summary (1S,2S)-1,3-Diacetoxy-1-(4-nitrophenyl)-2-propylisothiocyanate [(S,S)-DANI] has been developed as a new chiral derivatizing agent for resolution of compounds containing an amino group. The reagent is readily available in both enantiomeric forms. Its applicability was demonstrated by the resolution of representative α-amino acids. The diastereomeric thiourea derivatives produced were separated by reversed-phase (C₁₈) high-performance liquid chromatography, with mixtures of 0.1% aqueous trifluoroacetic acid (pH∼2) and methanol as eluents.     

Degradable dendritic polymers — A template for functional pores and nanocavities-

Degradable dendrimers are prepared as a template to create utrasmall cells when they get embedded in a polymer resin and to obtain well-defined cavities with particular chemical groups at their walls if the endgroups remain attached to the matrix. In a first approach cascade: (13-oxa-1-methylsilaundecenylidene): undecene was synthesised by the polyaddition reaction of methyl-di-undecenoxysilane as basic repeat unit. A multimodal weight distribution was found which appeared to be selfcontrolled to a limited molecular weight. Degradation was done with dry methanol and methanol with aqueous hydrochloric acid. In the case of dry methanol, the degradation products yielded only low molecular weight compounds while siloxane bonds were formed in the case the degradation was performed with methanol and aqueous hydrochloric acid. In order to create films with nanocavities, the degradable dendritic macromolecules were embedded in a methacrylate resin. Hole formation was illustrated by transmission electron microscopy for the case of 0.5 wt.-%, 5 wt.-% and 30 wt.-% of dendrimer content. However, aggregation of the dendritic molecules during the curing of the methacrylate resin could not be avoided. In order to suppress aggregation, cascade: (1-methylsilapropylidene): propene with methacrylate endgroups have been prepared which can be covalently linked to the embedding resin molecules. In a first approach the compatibility with the methacrylate resin was indicated by the optical transparency, while microscopy techniques were not capable to resolve the fine structure.     

Kinetics of the oxidation of cyclohexene by thallium(III) acetate

The kinetics of the reaction by which thallium(III) acetate oxidizes cyclohexene in glacial acetic acid medium, has been studied by UV spectrophotometric observation at 30°C. The consumption of thallium(III) acetate follows a second-order rate law exhibiting first-order dependence on each of thallium(III) acetate and cyclohexene; however, the first-order dependence on cyclohexene disappears at high cyclohexene concentrations as pseudo-first-order conditions prevail above 0.2 M cyclohexene. A steady-state model of the following form is proposed: where Tl, Cy, and Com are units of Thallium(III) acetate, cyclohexene, and a reaction complex. The value of k₂ has been evaluated as 0.00027 and (k_?1 + k₂) as 0.0385k₁. For low thallium(III) acetate concentrations the reaction kinetics follow the rate law: where α = the excess concentration of cyclohexene over thallium(III) triacetate. For thallium(III) acetate concentrations above 0.02 M, double salt formation of thallium(III) acetate with product thallium(I) acetate removes thallium(III) acetate from the reaction and a modified rate law is observed. Runge–Kutta numerical solutions to the differential equations provide confirmation that the rate expressions are valid in predicting the observed concentrations of thallium(III) acetate.     

质谱中若干金属配合物及簇合物的碎片重组反应

在质谱实验中,我们发现了与一般单分子分解反应相悖的四种类型碎片产物的重组反应物即(Ⅰ)裂解碎片的自组合产物如S_8~+及不同聚合度的聚硫离子;(Ⅱ)裂解碎片之间的相互组合物如[Fe(S_2CNC_4H_8)_3]~+和[Fe(S_2CNEt_2)_3]~+;(Ⅲ)裂解碎片的阴离子和阳离子部分碎片间的组合物如[Fe_2S_2(NO)_4(CH_3)_2]~+;(Ⅳ)歧化反应产物Cp_3Yb~+和YbL_3~+(Cp=C_5H_5),L=β-二酮)。本文阐述了这种重组反应或离子—分子反应在质谱条件下产生的可能性及其理论根据。     

Anhydro base of 4-(3-indolyl)pyrimidine

The reaction of 4-(3-indolyl)pyrimidine methiodide with alkali gives a stable anhydro base, which reacts under mild conditions with methyl iodide to give 1-methyl-4-(1-methyl-3-indolyl)pyrimidinium iodide. On the basis of the calculated molecular diagrams of both compounds it was concluded that they have high reactivities. The reaction of the anhydro base with an aqueous methanol solution of KOH, concentrated NH₄OH, hydrazine hydrate, and a mixture of malonic acid dinitrile with triethylamine leads to 3-acetylindole, 4-(3-indolyl)pyrimidine, 3(5)-(3-indolyl)pyrazole, and 2-amino-3-cyano-6-(3-indolyl)pyridine, respectively. 1-Methyl-4-(1-methyl-3-indolyl)pyrimidinium iodide under the same conditions gives similar compounds that contain a methyl group attached to the indole nitrogen atom. The structures of the synthesized compounds were confirmed by their IR, UV, PMR, and mass spectra.See [1] for our preliminary communication.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 212–218, February, 1982.     

Structure and dynamics of binary and ternary lanthanide(III) and actinide(III) tris[4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione] (TTA) complexes. Part 2, the structure and dynamics of binary and ternary complexes in the Y(III)/Eu(III)-TTA-tributylphosphate (TBP) system in chloroform as studied by NMR spectroscopy

The stoichiometric reaction mechanisms, rate constants and activation parameters for inter- and intramolecular ligand exchange reactions in the binary Y/Eu(TTA)(3)(OH(2))(2)-HTTA and the ternary Y/Eu(TTA)(3)(OH(2))(2)-TBP systems have been studied in chloroform using (1)H and (31)P NMR methods. Most complexes contain coordinated water that is in very fast exchange with water in the chloroform solvent. The exchange reactions involving TTA/HTTA and TBP are also fast, but can be studied at lower temperature. The rate constant and activation parameters for the intramolecular exchange between two structure isomers in Y(TTA)(3)(OH(2))(2) and Y(TTA)(3)(TBP)(OH(2)) were determined from the line-broadening of the methine protons in coordinated TTA. The rate equations for the intermolecular exchange between coordinated TTA and free HTTA in both complexes are consistent with a two-step mechanism where the first step is a fast complex formation of HTTA, followed by a rate determining step involving proton transfer from coordinated HTTA to TTA. The rate constants for both the inter- and intramolecular exchange reactions are significantly smaller in the TBP system. The same is true for the activation parameters in the Y(TTA)(3)(OH(2))(2)-HTTA and the ternary Y/Eu(TTA)(3)(TBP)(OH(2))-HTTA systems, which are ΔH(≠) = 71.8 ± 2.8 kJ mol(-1), ΔS(≠) = 62.4 ± 10.3 J mol(-1) K(-1) and ΔH(≠) = 38.8 ± 0.6 kJ mol(-1), ΔS(≠) = -93.0 ± 3.3 J mol(-1) K(-1), respectively. The large difference in the activation parameters does not seem to be related to a difference in mechanism as judged by the rate equation; this point will be discussed in a following communication. The rate and mechanism for the exchange between free and coordinated TBP follows a two-step mechanism, involving the formation of Y(TTA)(3)(TBP)(2).     

On the peroxyl scavenging activity of hydroxycinnamic acid derivatives: mechanisms, kinetics, and importance of the acid-base equilibrium

The peroxyl radical scavenging activity of four hydroxycinnamic acid derivatives (HCAD) has been studied in non-polar and aqueous solutions, using the density functional theory. The studied HCAD are: ferulic acid (4-hydroxy-3-methoxycinnamic acid), p-coumaric acid (trans-4-hydroxycinnamic acid), caffeic acid (3,4-dihydroxycinnamic acid), and dihydrocaffeic acid (3-(3,4-dihydroxyphenyl)-2-propionic acid). It was found that the polarity of the environment plays an important role in the relative efficiency of these compounds as peroxyl scavengers. It was also found that in aqueous solution the pH is a key factor for the overall reactivity of HCAD towards peroxyl radicals, for their relative antioxidant capacity, and for the relative importance of the different mechanisms of reaction. The H transfer from the phenolic OH has been identified as the main mechanism of reaction in non-polar media and in aqueous solution at acid pHs. On the other hand, the single electron transfer mechanism from the phenoxide anion is proposed to be the one contributing the most to the overall peroxyl scavenging activity of HCAD in aqueous solution at physiological pH (7.4). This process is also predicted to be a key factor in the reactivity of these compounds towards a large variety of free radicals.     

Influence of thallium(I) and thallium(III) on parameters of oscillating chemical reaction in a bromate-cerium(III,IV)-malonic acid-sulfuric acid system

The influence of thallium(I) and thallium(III) on the parameters of the Belousov-Zhabotinskii oscillating chemical reaction in the bromate-cerium(III, IV)-malonic acid-sulfuric acid system was studied. As a result of the addition of thallium(I) and thallium(III), the oscillation parameters change in the same way, which cannot be explained by the complexation of these ions with the bromide only. It was found that during the oscillating reaction, thallium(I) can be oxidized by bromine-containing compounds and thallium(III) reduced by the transformation products of malonic and bromomalonic acids. A scheme of action of a thallium(III)/thallium(I) two-electron redox pair in the oscillating chemical reaction studied has been proposed.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 23, No. 1, pp. 106–111, January–February, 1987.     

Determination of bromine in organic compounds by high-performance liquid chromatography

A method is proposed for the determination of bromine in organic compounds (which may also contain chlorine and iodine) by oxygen-flask combustion of the compound followed by pre-column reaction of bromide with acetanilide and 2-iodosobenzoic acid to form 4-bromoacetanilide which is then chromatographed on an ODS column with a mobile phase of methanol: water, 65:35 v/v, detection at 240 nm, and 4-N-acetylaminotoluene as internal standard. The method is rapid and precise (RSD 相似文献   

Hydride shift in the solvolysis of 5-substituted PGi1 derivatives

Silver ion mediated solvolysis of 5-iodo-PGI₁ derivatives as well as the reaction of PGF₂ methylester with thallium triacetate in acetic acid were studied with the aid of deuterium isotope labelling. In protic solvents (methanol, acetic acid) high retention (70–90%) of the deuterium label is compatible with a vicinal hydride shift whereas in non-protic solvents (e.g. pyridine) elimination occurs.     

两种异金属链状配位聚合物的合成和晶体结构

在甲醇溶液中,将K2NiL·H2O和M(OAC)2(M = Co,Zn)按1:1的摩尔比进行组装反应,得到了镍、钴和镍、锌两种异金属一维链状配位聚合物,其化学组成分别为{[Ni2Co2L2(H2O)2]·CH3OH·3H2O}n（1）和{[Ni2Zn2L2 (H2O)2]·2CH3OH·H2O}n（2）,（H4L=2-羟基-3-[(E)-({2-(2-羟基苯甲酰胺基)乙基}亚氨基)甲基]苯甲酸,OAC- = CH3COO-）。通过IR谱,元素分析的方法对其进行了表征,利用X-射线单晶衍射方法对其晶体结构进行了测定,结构分析表明：它们都是由不对称四核单元组成链状配位聚合物。     

Regiochemical Control and Suppression of Double Bond Isomerization in the Heck Arylation of 1-(Methoxycarbonyl)-2,5-dihydropyrrole

Arylation of 1-(methoxycarbonyl)-2,5-dihydropyrrole under standard Heck reaction conditions produces a mixture of compounds. The olefin undergoes two types of palladium-catalyzed reactions: (a) arylation to provide C-3 arylated derivatives and (b) competing double bond isomerization. Addition of silver carbonate and thallium acetate fully suppressed the isomerization, and good yields of C-3 substituted compounds were achieved after arylation with aryl halides. With regard to aryl triflates as arylating agents, addition of lithium chloride was necessary to promote the Heck reaction. This additive excluded the use of silver and thallium salts, but high regioselectivity and good yields could be obtained by employing tri-2-furylphosphine as ligand. Arylation was rendered both regioselective and enantioselective (58% ee) with 1-naphthyl triflate as substrate utilizing a (R)-BINAP/thallium acetate combination. The C-3 arylated enamides were converted further into the corresponding 3-arylpyrrolidines.