A new tetrahedrally distorted copper(II) complex derived from disulphide coupled N-(2-ethanethiol)salicylideneimine

Copper(II) acetate reacts with N-(2-ethanethiol)salicylideneimine forming an ONNO chelate of α,α′-(diethylenedisulphide)-N,N′-disalicylideneimine with an uncoordinated disulphide. This copper(II) complex can also be obtained in higher yield if the thiol is first oxidized to disulphide with iodine. The geometry about copper(II) is distorted from planar to a flattened tetrahedron.     

Reactivity of some cuprous salts towards tenmembered macrocyclic disulphides: A new route to the synthesis of Cu(II)-thiolates

Cuprous ion is found to be quite reactive towards disulphide present in a macrocycle. Thus, when [Cu(MeCN)₄] BF₄ or [Cu(MeCN)₄]ClO₄ is allowed to reflux in acetonitrile with a ten-membered macrocycle containing two amino nitrogens and one disulphide donor in an atmosphere of nitrogen, electron transfer takes place from the metal centre to the disulphide group. As a result, copper is oxidised to the + 2 state and the disulphide reduced to thiolates. The thiolates then bind the Cu(II) and form discrete and neutral CuN₂S₂ complexes. Syntheses of two new CuN₂ S₂ complexes have been achieved following this route. The reactions take place smoothly and give the desired product in excess of 25% yield with respect to the macrocycle. Electronic absorption spectral results are consistent with a nearly square planar geometry. Each of the two complexes isolated exhibits quasireversible Cu(II)/Cu(I) couple with E_f near — 0.3 V vs SCE. Both the complexes are further characterised by room temperature magnetic susceptibility, EPR spectroscopy at 298 and 77 K and elemental analyses.     

Characterization of the antioxidative activity of novel nontoxic neuropeptides by using capillary electrophoresis

In the present study, we have monitored the oxidation process of novel nontoxic neuropeptides and determined its rate constants, which describe the antioxidative potential of the peptides. A capillary electrophoretic method was implemented which ensures the simultaneity of analysis of reactants and products in a short time of analysis. The rate constants of oxidation of the four novel peptides, 4-methoxy-L-tyrosinyl-gamma-L-glutamyl-L-cysteinyl-glycine (UPF1), D-serinyl-gamma-L-glutamyl-L-cysteinyl-glycine (UPF6), 4-methoxy-L-tyrosinyl-alpha-L-glutamyl-L-cysteinyl-glycine and D-serinyl-alpha-L-glutamyl-L-cysteinyl-glycine, designed by us, were compared with those of oxidation of glutathione (reduced glutathione) by using capillary electrophoresis. The second-order rate constants were similar for all peptides if the oxidation was carried out with hydrogen peroxide (k(II) = 0.208 - 0.236 x 10(3)/M.min). The rate constants were also determined for the mixtures of peptides. When the oxidation is caused by hydroxyl radical (OH*), the gamma-glutamate containing peptides (UPF1 and UPF6) exhibited two to four times higher antioxidative activity (k(II) = 4.428 and 2.152 x 10(3)/M.min, respectively). The results suggest that the antioxidative potential of the peptides studied is not determined by the formation of disulphide bridge alone.     

Direct oxidimetric determination of thiocarbonate sulphur with ferricyanide, using iron(II)-dimethylglyoxime or sodium nitroprusside as indicator

Direct determination of 15-50 mg of thiocarbonate sulphur can be achieved by a one-step titration with potassium ferricyanide, using iron(II)-dimethylglyoxime or sodium nitroprusside as indicator. Only one sulphur atom of the thiocarbonate ion undergoes oxidation to elemental sulphur, the other two separating as carbon disulphide.     

A polarographic study of the redox and complex-forming reactions of penicillamine, N-acetylpenicillamine and copper (I) or (II)

Polarographic methods are used to study the redox and complexation reactions between copper(II) or (I) and penicillamine, N-acetylpenicillamine or the oxidation product, dithiobisvaline. The formation of a 1:1 copper(I) complex between penicillamine and copper(I) was proved, and the stability of the complex measured. Copper(II) oxidizes the sulphur compound to the disulphide and the copper(I) formed then forms a complex with the sulphur amino-acid. The greater stability of the non-acetylated copper(I) complex suggests that RSCu(I) contains a chelate ring with participation of the free amino group. The disulphide can only form a complex with copper(II) and the stability of this complex is low. The results suggest that the copper(I) chelate is the form in which copper is eliminated during treatment with penicillamine.     

New tests for the detection of azide

Two new, simple, reliable, and specific colour tests are described for the detection of azide. In one, the azide is heated with allyl isothiocyanate and water to form 1-allyl-2-tetrazoline-5-thione in solution; the latter gives a yellow precipitate on treatment with bismuth nitrate solution. Pyridine enhances the intensity of the colour. The allyl isothiocyanate can be produced in situ by treating allylamine with carbon disulphide, diethylamine and hydrogen peroxide. In the other test the azide is heated with carbon disulphide, water and acetone, resulting in the formation of 1,2,3,4-thiatriazoline-5-thione which gives a yellow precipitate with Cu(II) or Bi(III). Pyridine again enhances the colour. The method is applicable to 5-10 mg of soluble azides, but insoluble azides cannot be tested. CN(-), SCN(-), and other common anions do not interfere. Only S(-2) interferes by masking the colour (black CuS or Bi(2)S(3) is precipitated). NO(2)(-) in larger amounts interferes in the second test.     

Preconcentration of copper,cadmium, mercury and lead from sea and tap water samples on a dithiocarbamatecellulose derivative

Ethylenediamine, 2,2'-diaminodiethylamine, and triethylenetetramine (trien) were introduced onto microcrystalline cellulose after tosylation. Dithiocarbamate (DTC) groups were introduced by reaction with carbon disulphide. The metal uptake behaviour of these amine- and dithiocarbamate-cellulose derivatives were compared for Cu(II), Cd(II), Pb(II), Hg(II), Co(II), and U(VI). The trien—DTC-cellulose was used to preconcentrate Cu(II), Cd(II), Hg(II), and Pb(II) from sea and tap water.     

Effect of solute-co-ordinating solvent interactions and temperature on the EPR and electronic spectra of bis(dithiophosphato)copper(II)

The self-redox reaction proceeding between two molecules of the complex bis(disubstituted-dithiophosphato)copper(II), CuII(R2-dtp)2, is studied by EPR and UV-VIS spectroscopy in DMFA, DMSO and pyridine. The effect of temperature and disulphide concentration in the solutions is also evaluated. The EPR spectra show that the g-values of CuII(R2-dtp)2 increase when it is dissolved in co-ordinating solvents, whereas the copper hyperfine splitting decreases compared to the corresponding values in non-co-ordinating solvents. Under the same conditions, a hypsochromic shift is observed in the maximal absorption at 420 nm of the electronic spectra which corresponds to the ligand-to-metal charge-transfer (LMCT) transition of the complex. The results are explained with the formation of axial or equatorial adducts between CuII(R2-dtp)2 and the co-ordinating solvents used. On the other hand, the molar absorptivity of the LMCT band and the intensity of the EPR spectrum increase strongly with the nature of the used co-ordinating solvent, the time after dissolution and the quantity of added disulphide. Both also depend on the size and shape of remote ligand substituents and they increase in the order Me < Et < i-Pr. Beer's law is not obeyed immediately after dissolution of copper bis-dithiophosphate complexes. However, after standing for 24 h in the dark, DMFA solutions exhibit linear absorption/concentration dependence with approximately 70% higher molar absorptivity. An additional increase of the LMCT band and EPR intensity is found after heating the solution up to 50 degrees C for a short time, as well as after addition of the corresponding disulphide of dithiophosphate [(RO)2P(S)S-S(S)P(RO)2] to the CuII(R2-dtp)2 solution. As a result, the molar absorptivity value at the maximum of the LMCT band of Cu[(i-PrO)2-dtp]2 increases from 7.9 x 10(3) m(-1) dm3 cm(-1) immediately after dissolution to 2.9 x 10(4) m(-1) dm3 cm(-1). In DMSO and pyridine, the intensity of both the EPR signal and LMCT band of CuII(R2-dtp)2 continuously decrease after the preparation of the solutions. A small increase is only observed immediately after the addition of the corresponding disulphide of dithiophosphate. While DMFA forms stable adducts with Cu[(i-PrO)2-dtp]2, adduct formation with DMSO and pyridine destroys the initial complex.     

The electrochemical synthesis ofO-ethylxanthato- andN,N′-dimethyldithiocarbamato-complexes of oxovanadium(IV), manganese (III), zinc(II), silver(I) and cadmium(II)

Summary A direct electrochemical synthetic method has been developed to effect the one-step preparation of metal xanthates and dithiocarbamates by the oxidation of the metal in an organic solution of the dixanthogen or thiuram disulphide. Results are reported for the metals: oxovanadium(IV), manganese(III), zinc(II), silver(I) and cadmium(II).     

Some Reactions of 5-(3 or 4-Pyridyl)-1,3,4-Oxadiazoles with Amines and Hydrazines

2-Amino-and 2-hydrazino-5-(3 or 4-pyridyl)-1, 3, 4-oxadiazoles [II_i-k] have been prepared by racting 2-chloro derivatives with the corresponding amines or hydrazines, the 2-hydrazino (II_i-k) compounds that obtained were heated with carbon disulphide and alcoholic potassium hydroxide where 5-(3 or 4-pyridyl)-1,3,4-oxadiazolo (2,3-C)-1,2,4-triazole 5-thione (III_a-c) were obtained, the given structures were biologically screened.     

Estimation of mercaptans with 1-chlorobenzotriazole

A simple but accurate potentiometric method for the estimations of mercaptans in 0.01M perchloric acid has been developed, based on their oxidation with 1-Chlorobenzotriazole. Quantitative oxidation solely to the disulphide stage is ensured by using critical amounts of methanol, acetonitrile and potassium iodide. Chloride, mercury(II) and copper(II) interfere. A back-titration procedure can also be used. The oxidation products have been identified.     

Polycondensed heterocycles. III. Synthesis of 5,11-dioxo-1,2,3,1 1a-tetrahydro-5H,11H- and 5-oxo-2,3,11,1 1a-tetrahydro-1H,5H-pyrrolo[2,1-c][1,4]benzothiazepine

The syntheses of 5,11-dioxo-1,2,3,11a-tetrahydro-5H11H- and 5-oxo-2,3,11,11a-tetrahydro-1H,5H-pyrrolo-[2,1-c][1,4]benzothiazepine 10 and 11 have been studied. The former was obtained by intramolecular cyclization with CDI of N-(2-mercaptobenzoyl)-L-proline 19 , prepared on one hand by demethylation of N-(2-methylthiobenzoyl)-L-proline t-butyl ester 15 , obtained via the Pummerer rearrangement of the corresponding sulphoxide 17 and successive alkaline hydrolysis, and by deprotection of the mercapto ester 18 with TFA or trimethylsilyl iodide. The ester 15 was achieved by reaction of o-(methylthio)benzoic acid 12 with L-proline t-butyl ester or by treatment of the corresponding acid chloride 13 with L-proline and successive esterification of N-(2-methylthiobenzoyl)-L-proline 16 . On the other hand the proline 19 was also obtained by reduction with sodium dithionite of (S)-bis[2-[[2-(hydroxycarbonyl)-1-pyrrolidinyl]carbonyl]phenyl] disulphide 20 , prepared by condensation of bis(2-chlorocarbonylphenyl) disulphide 14 with L-proline. The reduction of (S)-bis[2-[[2-(chloromethyl)-1-pyrrolidinyl]carbonyl]phenyl] disulphide 28 with sodium borohydride in boiling ethanol afforded directly the benzothiazepinone 11 in 85% yield. The disulphide 28 was synthesized treating the corresponding alcohol 24 or N-(2-mercaptoben-zoyl)-L-prolinol 25 with thionyl chloride. Compound 25 was obtained by demethylation of the corresponding methylthio ether 26 oxidized to sulphoxide 27 via the Pummerer rearrangement. The acid chloride 14 by condensation with (S)-2-(chloromethyl)pyrrolidine hydrochloride gave disulphide 28 as well. The acid chlorides 13 and 14 by reaction with L-prolinol provided respectively alcohols 26 and 24 . Attempts to cyclodehydrate the mercapto alcohol 25 , obtained also by reduction of disulphide 24 , failed.     

GC-MS法测定大蒜中的挥发性物质

大蒜(AlliumsatiuvmL.)是多年生草本百合科植物大蒜的鳞茎,按皮的颜色不同可分为紫皮蒜和白皮蒜两种。大蒜原产于意大利的西西里岛,约在两千多年前传入我国。大蒜不仅是极佳的调味食品,而且还有很好的药用功能。近年来,科学家研究证明,大蒜是一种健康食品,有助人体防病保健、延年益寿,是药食兼优的佳品,对人体具有多种药用价值。大蒜具有一种强烈的蒜臭气味,这种特殊的气味由许多复杂的硫化物组成。这类有机硫化物可促进消化,健胃整肠,强化抗菌作用,消肿止痛,改善机体机能的功能,大蒜中还含有乙烷硫代磺酸乙酯和二烯丙基三硫化物等,能阻断强烈致癌物质亚硝胺类在胃部的形成和积累,可预防胃癌、食道癌、肝癌、鼻咽癌的发生。本试验采用"同时蒸馏-萃取方法"(simultaneousdistillationandextraction,SDE)提取白皮和紫皮大蒜的挥发性成分,经GC-MS分析,确定了化合物的化学组成和相对百分含量。     

Polarographic study of bis(2-pyridyl)disulphide di-N-oxide and bis(2-quinolyl)disulphide di-N-oxide in aqueous ethanol

The polarographic reduction of bis(2-pyridyl)- and of bis(2-quinolyl)disulphide di-N-oxide in aqueous alcohol yields aryl mercaptans. The electrode reaction is kinetically controlled by an initial one-electron transfer step, and values for the transfer coefficients and the specific heterogeneous rate constants for the forward reactions are presented. The polar N-oxide function in the alpha-position withdraws electrons from the disulphide bond, making the half-wave potential less negative than that of the diphenyl disulphide. The pk(a) values of the mercapto compounds formed have been evaluated and the low values obtained for the heterocyclic N-oxides are further evidence for tautomerism in these compounds.     

1,3-二联苯基-2，4-二吡啶基环丁烷的结构与光化学性质

通过反-1-(4-联苯基)-2-(4-吡啶基)乙烯(EI)在稀硫酸中的光二聚反应合成了r-1,c-2,t-3,t-4-1,3-双(4-联苯基)-2,4-二(4-吡啶基)环丁烷(II).用X射线衍射法测定了其结构.晶体II为单斜晶系,空间群为P2     

Analytical applications of graphite electrode modified with Bis(diisopropyloxithiophosphon)Disulphide

A modified graphite electrode was produced by adsorption the bis(diisopropyloxythiophosphone)disulphide {(i-PrO-)(2)P(S)S-}(2) under vacuum. Its electrochemical characteristics in flowing stream were described. The modified electrode has been used for simultaneous determination of Cu(II), Ag(I) by flow injection anodic stripping voltammetry.     

A thermogravimetry/differential thermal analysis,evolved gas analysis and pyrolysis/gas chromatography—mass spectrometry study of tetrakis (diethyldithiocarbamato)tin(IV)

The thermal decomposition of tetrakis(diethyldithiocarbamato)tin(IV) has been studied by TG/DTA, EGA and P/GC-MS techniques. From the P/GC-MS analysis, it is apparent that the denticity of the dithiocarbamate ligand influences the mechanism of decomposition. Initially, the monodentate ligands decompose by a radical mechanism to form tetraethylthiuramdisulphide which decomposes further into carbon disulphide and diethylamine. The intermediate formed, bis(diethydithiocarbamato)tin(II), decomposes in two different ways. The bidentate ligands decompose with the liberation of carbon disulphide and tetraethylthiourea, whereas the monodentate ligands, formed as a result of the high temperatures, decompose to produce S-ethyl N,N-diethyldithiocarbamate and ethylisothiocyanate. The overall thermal decomposition mechenism of tetrakis(diethyldithiocarbamato)tin(IV) is complex and the primary decomposition involved both ionic and radical recombination reactions.     

Oxidation of l-cysteine,mercaptoacetic acid and β-mercaptoethylamine by 12-tungstocobaltate(III)

The stoichiometries and kinetics of the reactions of 12-tungstocobaltate(III) with L-cysteine, mercaptoacetic (thioglycollic) acid and β-mercaptoethylamine have been investigated in aqueous perchloric acid solution over a wide concentration range and at an ionic strength of 1.0 mol dm^?3 (NaClO₄). One mole each of the thiols is required to reduce 12-tungstocobaltate(III) to 12-tungstocobaltate(II) ions, with the disulphide of the thiol as the other product. The rates of reactions decrease with increasing acidity and there is no evidence for the formation of an intermediate complex of significant stability. The reactions are interpreted in terms of an outer-sphere mechanism.     

Divalent transition metal complexes

4-(4-ethoxy-phenylhydrazono)-1-phenyl-3-methyl-1H-pyrazolin-5(4H)-one (5a) (H-EMPhP) as ligand and its Cu(II), Co(II) and Ni(II) complexes 4(a-c) were synthesized and characterized by their thermal and spectral properties. The azocoupling product (H-EMPhP), able of azo-hydrazone tautomerism 5(a-d), act as a bidentate ligand involving in coordination the azogroup nitrogen of its common anion (7) and the oxygen atom that is bound to the pyrazole ring of the mentioned anion (7).     

Alkyl and cyclic substituted thiuram disulphides as ligands. titanium(iv), vanadium(iv), and oxovanadium(iv) complexes

Summary Titanium(IV) hexacoordinate thiuram disulphide complexes of the type [TiX₄R₂NC(S)SSC(S)NR₂}] (X=Cl or Br; R=Me, Et, piperidinyl or morpholinyl) have been prepared by reaction between TiX₄ (X=Cl or Br) and the thiuram disulphide. Similar reactions with VOCl₃ lead to reduction of vanadium(V) and give rise to the oxovanadium(IV) pentacoordinate complexes [VOCl₂{R₂NC(S)SSC(S)NR₂}]. However, the reactions of these same thiuram disulphide ligands with [VCl₂(THF)₂] (THF=tetrahydrofuran) cause oxidation of vanadium and to the reduction of the disulphide to the corresponding dithiocarbamate [R₂NCS₂]^–, resulting in new dichlorobis (dithiocarbamate)vanadium(IV) complexes [VCl₂-(R₂NCS₂)₂]. All the compounds have been characterized by elemental analyses, i.r., visible and e.p.r. spectra. Both thiuram disulphides and dithiocarbamate ligands exhibit bidentate