Exchange constants of Al(III) and Fe(III) on Dowex 50W-X8

The exchange constants tor Al³⁺ and Fe³⁺ ions on the cation-exchange resin Dowex 50W-X8 (H⁺-form) are reported. A batch method of equilibrium at room temperature was used to determine these constants, which are Al³⁺ + 3HR AIR₃ + 3H⁺, K = 1·66 Fe³⁺ + 3HR FeR₃ + 3H⁺, K = 2·19 R denoting the resin.     

The Behaviour of Some Phenolic Acids and Aldehydes on Thin Layers of Silica Gel Impregnated with Fe(III)

Abstract

The behaviour of phenolic aldehydes and acids commonly found in lacustrine sediments as degradation products of lignine was tested by thin layer chromatography on silica gel plates plain and impregnated with Fe(III) in different solvent systems. The differences expressed as R_i values can be used as one of the parameters in the identification of some phenolic aldehydes or acids.     

高效液相色谱法分析矿泉水中酚类化合物

用带荧光检测器的高效液相色谱法同时测定了矿泉水中的苯酚、甲酚、双酚Ａ、双酚Ｆ、４－叔丁酚、双酚Ａ二环氧甘油醚和双酚Ｆ二环氧甘油醚等,水样经液－固萃取浓缩后再进行分析,检测限可达０．１～０．２μｇ／Ｌ。重复测定的标准偏差为１．１２％～１３．２１％,水样测定的回收率为８１％～１０５％。     

Variable Dimensionality of Europium(III) and Terbium(III) Coordination Compounds with a Flexible Hexacarboxylate Ligand

A reaction between 4,4′,4″-(benzene-1,3,5-triyltris(oxy))triphthalic acid (H₆L) and lanthanide(III) nitrates (Ln = Eu³⁺, Tb³⁺) in water under the same conditions gave a molecular coordination compound [Tb(H_4.5L)₂(H₂O)₅]∙6H₂O in the case of terbium(III) and a one-dimensional linear coordination polymer {[Eu₂(H₃L)₂(H₂O)₆]∙8H₂O}_n in the case of europium(III). The crystal structures of both compounds were established by single-crystal X-ray diffraction, and they were further characterized by powder X-ray diffraction, thermogravimetric analysis and infrared spectroscopy. The compounds demonstrated characteristic lanthanide-centered photoluminescence. The lanthanide-dependent dimensionality of the synthesized compounds, which are the first examples of the coordination compounds of hexacarboxylic acid H₆L demonstrates its potential as a linker for new coordination polymers.     

An Application of the Ligand Exchange Chromatography to the Analysis of Some Protein Components

Abstract

The resolution of a mixture containing some α-aminoa-cids, theirβ-isomers and dipeptides is realized on column by the ligand-exchange (LE) chromatography. The support used is a chelating exchanger bounded with a copper(II)- or a nichel(II)-ammonia complex.     

硫酸锌结晶水合物用作气相色谱固定相测定酚类化合物

采用硫酸锌结晶水合物作气相色谱固定相,加入己二酸二胆甾醇酯作改性剂,将富集后的酚类样品进行了有效的分离。平均回收率为９８．８９％～１０１．９２％,变异系数为１．１％～４．１％。     

Adducts of Niobium (V) and Tantalum (V) Halides. XV. Ligand Exchange of the Adducts with Some Phosphoryl Compounds

The ligand exchange MX₅·L + *L?MX₅·*L + L for the octahedral adducts MX₅·L, in an inert solvent (CH₂Cl₂ or CHCl₃) with neutral ligands, proceeds via a dissociative D mechanism when M = Nb, X = Cl and L = phosphoryl compound. A dissociative interchange I_d mechanism is suggested when M = Nb or Ta, and X = F. A first order rate law and positive values for ΔS* (+4 to +14 cal K^?1 mol^?1) are observed for the exchanges on the pentachloride adducts. However, a second order rate law and large negative values for ΔS* (-15 to -24 cal K^?1 mol^?1) are found for the intermolecular neutral ligand exchange (measured by ¹H-NMR.) and for the intramolecular fluorine exchange (measured by ¹⁹F-NMR.) reactions on the pentafluoride adducts. The fluorine exchange is 2 to 5 times faster than the ligand exchange. The exchanges, on the pentachloride and on the pentafluoride adducts, are slowed down with increasing donor strength of the phosphoryl compound.     

Retention Mechanism of Phenolic Compounds in Subcritical Water Chromatography

The transfer enthalpies and entropies of hydroxyl and nitryl in different mobile phase systems were compared by van't Hoff curve. Results suggest that the presence of acetonitrile and methanol in the mobile phase may decrease the interaction of solute and stationary phase with respect to subcritical water, thereby reducing the contribution of enthalpy to the retention. Retention mechanisms of phenolic compound appear to be more similar in subcritical water and water/methanol systems on the PRP-1 column. Hydrogen bond in subcritical water system plays a very important role in the retention of the phenols.     

Studies on the Air Oxidation of Some Arsenic(III) Compounds

The air oxidation of As(III) oxides [(PhAsO) _x and Ph₂As-O-AsPh₂] and thioesters [Ph-As(SPh)₂, Ph₂As-SPh Me-As(SPh)₂, Me₂As-SPh], in chloroform and in methanol was studied. The air oxidation in chloroform was faster probably because the solubility of dioxygen is greater than in methanol, and it is favored by the electron-withdrawing phenyl groups bound to As(III). The products obtained were the arsonic or arsinic acids and diphenyl disulfide. In one case, diphenyl disulfide and thiophenol were produced. The results can be rationalized by assuming first hydrolysis of the As(III) compounds to arsonous or arsinous acids followed by their oxidation to arsonic and arsinic acids, which should involve the binding of dioxygen to As(III). The other hypothesis assumes first the binding of dioxygen to As(III) of these oxides and thioesters followed by the decomposition of the adducts. The binding of the ground state dioxygen to As(III) may have biochemical implications for toxicity or chemotherapy of arsenic(III) compounds.     

Some Aspects of Chiral Separations in Planar Chromatography Compared with HPLC

JPC – Journal of Planar Chromatography – Modern TLC - The paper reviews the latest achievements in chiral separation by planar chromatography (PC) since 2001. The emphasis is on...     

Two Novel Zinc Compounds with in situ Formation of Dimethylamine Ligand

The investigation of the supramolecular interactions between the zinc chloride salts and the crown ether in tetrahydrofuran （THF） with the diffusion of in situ formed DMA （DMA = dimethylamine） ligand leads to two novel zinc-DMA compounds, [（H3O）·（18C-6）][ZnCl3（DMA）] 1 and [（HDMA）·（18C-6）][ZnCl3（DMA）] 2 （18C-6 = 18-crown-6）, whose emissions fall into the blue-emission field. Crystal data for compound 1： monoclinic, space group P21/c, a = 8.753（1）, b = 14.538（2）, c = 19.969（3）A, β = 110.121（7）°, V = 2386.2（5）A^3, T = 293（2） K, Z = 4, Mr = 500.14, Dc= 1.392 g/cm^3,μ = 1.395 mm^-1, F（000） = 1048, S = 1.006, R = 0.0611 and wR = 0.1755 for 3676 observed reflections with I 〉 2σ（I） and 235 parameters. For 2： triclinic, space group P1^-, a = 9.2672（4）, b = 11.8778（2）, c = 13.3846（1） A, a = 67.09（1）, β = 75.54（2）, ）,γ = 81.32（2）°, V = 1311.74（6） A^3, T = 293（2） K, Z = 2, Mr = 527.21, Dc = 1.335 g/cm^3,μ = 1.271 mm^-1, F（000） = 556, S = 1.006, R = 0.0393 and wR = 0.1034 for 3839 observed reflections with I〉 2σ（I）.     

Hydrophilic-Interaction Planar Chromatography of Some Water-Soluble Co(III) Complexes on Different Adsorbents

JPC – Journal of Planar Chromatography – Modern TLC - The chromatographic behavior of twelve neutral, mixed cobalt(HI) complexes of the uns-cis-edda-type has been investigated in six...     

Some aspects of the solvent extraction of Fe(II) and Fe(III) from an aqueous acidic medium containing Cr(III)

The separation of Fe(II) and Fe(III) from an aqueous acidic sulphate medium containing Cr(III) was investigated. It was found that the Fe(II) and Fe(III) can be removed from the aqueous phase using Aliquat 336 thiocyanate as solvent extractant. The Fe(II) is extracted as the Fe(NCS)₄²⁻ species while Fe(III) is extracted as Fe(NCS)₅²⁻ species. The effects of pH, extractant concentration and thiocyanate added to the aqueous phase were investigated.     

Some physical and chemical properties of Fe(II)X,Fe(II)Y and Fe(III)Y zeolites

Fe(II)Y, Fe(III)Y and Fe(II)X zeolites of high iron content have been prepared by replacing the sodium ions with Fe²⁺ or Fe³⁺ by means of an ion-exchange procedure. Chemical, TG, DT and X-ray analyses of these zeolites have been made and the IR spectra recorded. The results of physical-chemical analyses are discussed in terms of unit-cell composition and mechanical and thermal stability of the crystal framework.     

Studies on the Efficiency of Iron Release from Fe(III)-EDTA and Fe(III)-Cit and the Suitability of These Compounds for Tetracycline Degradation

Iron ions can be used to degrade tetracycline dispersed in nature. Studies of absorption and fluorescence spectra and quantum chemistry calculations showed that iron is more readily released from Fe(III)-citrate than from Fe(III)-EDTA, so Fe(III)-citrate (Fe(III)-Cit) is more suitable for tetracycline (TC) degradation. At 30 °C, a severe degradation of TC by Fe(III)-Cit occurred as early as after 3 days of incubation in the light, and after 5 days in the dark. In contrast, the degradation of TC by Fe(III)-EDTA proceeded very slowly in the dark. By the fifth day of incubation of TC with Fe(III)-Cit in darkness, the concentrations of the former compound dropped by 55% and 75%, at 20 °C and 30 °C, respectively. The decrease in tetracycline concentrations caused by Fe(III)-EDTA in darkness at the same temperatures was only 2% and 6%, respectively. Light increased the degradation rates of TC by Fe(III)-EDTA to 20% and 56% at 20 °C and 30 °C, respectively. The key role of the light in the degradation of tetracycline by Fe(III)-EDTA was thus demonstrated. The TC degradation reaction showed a second-order kinetics. The rate constants of Fe(III)-Cit-induced TC degradation at 20 °C and 30 °C in darkness were k = 4238 M⁻¹day⁻¹ and k = 11,330 M⁻¹day⁻¹, respectively, while for Fe(III)-EDTA were 55 M⁻¹day⁻¹ and 226 M⁻¹day⁻¹. In light, these constants were k = 15,440 M⁻¹day⁻¹ and k = 40,270 M⁻¹day⁻¹ for Fe(III)-Cit and k = 1012 M⁻¹day⁻¹ and 2050 M⁻¹day⁻¹ at 20 °C and 30 °C; respectively. A possible reason for the higher TC degradation rate caused by Fe(III)-Cit can be the result of its lower thermodynamical stability compared with Fe(III)-EDTA, which we confirmed with our quantum chemistry calculations. Two quantum chemistry calculations showed that the iron complex with EDTA is more stable (the free energy of the ensemble is 15.8 kcal/mol lower) than the iron complex with Cit; hence, Fe release from Fe(III)-EDTA is less effective.     

The Flipping of CO Ligand Groups in Metal Carbonyl Compounds and its Frequency in Fe(CO)5

It has been proven qualitatively by a number of authors using variable temperature NMR experiments that most metal carbonyl complexes are nonrigid. A quantitative determination of the ligand exchange frequency v_e is often achieved by a line shape analysis or by measurement of the transverse relaxation time T₂ using the Carr-Purcell method. In the case of a “very fast” exchange, however, both methods prove unsuccessful. It is shown in this study that a simultaneous fit of IR or Raman spectra on the one hand and NMR spectra on the other can make possible the determination of v_e for the “very fast” exchange and can also facilitate the determination of v_e in “slow” and “medium” exchange cases considerably. The ligand exchange frequency thus found for Fe(CO)₅, 1.1 × 10¹⁰s^?1, is unexpectedly high; comparison with variable temperature measurements on solid Fe(CO)₅, yields similar energy barriers. A mechanism of exchange closely related to the “Berry mechanism” is proposed. Finally the consequences of this surprisingly large ligand exchange rate are discussed with respect to IR band assignments for molecular “fragments” M(CO)^x (where x=coordination number, and M is a transition metal, typically lanthanoid or actinoid).     

Adsorption behavior of Fe(II) and Fe(III) ions on thiourea cross-linked chitosan with Fe(III) as template

A new type of thiourea cross-linked chitosan with Fe(III) as template (TCCTS template) was synthesized. The adsorption of Fe(II) and Fe(III) on this TCCTS template was studied. The factors affecting adsorption such as pH and contact time were considered. The results showed that the optimum pH value for adsorption was pH = 5.0 and the adsorption equilibrium time was about 60 min. The adsorption isotherms and kinetics were investigated, and the equilibrium data agreed very well with the Langmuir model and the pseudo second-order model could describe adsorption process better than the pseudo first-order model. Results also showed that TCCTS template was a favourable adsorbent for Fe(II) and Fe(III) in aqueous solution.     

Synthesis and Physicochemical Properties of Terbium(III) and Gadolinium(III) Coordination Compounds with Some Alkyloxybenzoic Acids

Russian Journal of General Chemistry - New coordination compounds of terbium(III) and gadolinium(III) with alkoxybenzoic acids and 1,10-phenanthroline were prepared by the electrochemical synthesis...     

超声波提取-气相色谱法测定油田区土壤中21种酚类化合物

采用超声波提取—气相色谱法测定油田区土壤中21种酚类化合物,主要研究了提取时间及净化条件等对测定结果的影响.对比了加压流体萃取与超声波提取方式对回收率的影响,结果表明:超声波提取法回收率优于加压流体萃取法,其中2,4-二硝基酚和4-硝基酚两种化合物比加压流体萃取法回收率提高了30%.以10.0 g土壤样品计,酚类化合物的检出限为0.01～0.05 mg/kg,样品加标回收率为81.5%～110%,精密度为2.6%～11%.经有证标准物质验证,相对误差为2.6%～14%.试验结果表明,超声波提取法适合于油田区土壤中21种酚类化合物的测定.