Xanthate Compounds Research Articles

Decarboxylative Xanthylation under Photocatalytic Conditions.

Xanthates are widely used in organic synthesis for the construction of various molecules and have numerous applications as bioactive compounds. Here, we present their preparation via a straightforward photocatalytic decarboxylative xanthylation process involving readily available oxime esters and xanthate dimers. This approach provides access to a wide variety of xanthate compounds in moderate to good yields, including xanthates derived from relevant pharmaceutical and bioactive molecules.

Awaruite (Ni3Fe), a new large nickel resource: Electrochemical characterization and surface composition under flotation-related conditions

Awaruite is a native nickel–iron alloy (Ni3Fe), found in serpentinized ultramafic rocks, that has gained interest as a possible source of nickel. FPX Nickel is advancing a very large awaruite deposit in central British Columbia, Canada, on which this work is based. To date there is limited information available regarding the flotation conditions to selectively concentrate awaruite from gangue minerals in serpentinite ores. The aim of this work was to investigate the floatability of awaruite in different solution conditions with a xanthate collector. Awaruite readily floated in acidic solution with a xanthate collector but not in neutral and alkaline solutions. Voltammograms on awaruite indicated that the alloy shows an active passive transition behaviour in acidic solution and passive behaviour in neutral and alkaline solutions. The passivation layer formed in neutral and alkaline solutions showed to inhibit the interaction between xanthate and awaruite surface. Infrared spectra on awaruite showed the presence of xanthate compounds attached to the surface in acidic condition at potentials higher than the reversible potential of xanthate/dixanthogen. Based on experimental results, it was postulated that xanthate chemisorbs on awaruite and then it oxidizes to form dixanthogen. Also, it was demonstrated that when passivated, awaruite quickly activates in acidic solution, good flotation performance was achieved with 10 min of conditioning, and similar performance was obtained after 30 min of conditioning. This work serves as a confirmation that is possible to float awaruite using xanthate, a well-known collector that offers selectivity over oxides and silicate minerals, which are the main gangue minerals in serpentinite ores.

Inverse gas chromatography analysis of minerals: Pyrite wettability

Inverse gas chromatography (IGC) is a powerful technique for characterizing the physicochemical properties of a wide variety of materials. The behaviour of minerals in the flotation process is directly related to their wettability, which can be described by surface free energy. In this work, the adsorption of copper and xanthate on hydrophilic pyrite, prepared under different conditions, was studied using X-ray photoelectron spectroscopy (XPS) and IGC. Microflotation experiments were also conducted to determine flotation recovery. The XPS analyses confirmed the presence of copper (I) and xanthate compounds on the surface of treated samples. The surface energy and work of adhesion to water decreased, while the flotation recovery increased due to treatment.IGC has been shown to have the capability of characterizing mineral surfaces, pre- and post-treatment. It enabled the observation of the changes in physicochemical properties of pyrite surface due to surface modification at different conditions. Moreover, combining the microflotation recovery of the samples with IGC results confirmed the correlation between surface energy and flotation response.

Soluble Xanthate Compounds for the Solution Deposition of Metal Sulfide Thin Films

AbstractA series of soluble metal ethylxanthate compounds was synthesised as precursors for metal sulfide thin films to be deposited using solution‐based techniques. Initially, a range of air‐ and moisture‐stable organic ethylxanthate (EtXn) salts were synthesised (cation=Me4N (1), Et4N (2), Pr4N (3), Ph4P (4), guanidinium (5), NMeH3 (6), NMe2H2 (7), NMe3H (8), NH4 (9)). Thermogravimetric analysis (TGA) was used to examine their decomposition profiles, which in turn informed the decision of which counter cation was best suited for inclusion in the metal xanthate compounds. Periodic NMR spectroscopy studies and single‐crystal X‐ray diffraction (SXRD) were used to determine the role protic ammonium counter cations play in the detrimental conversion of xanthates to dithiocarbamate anions. The organic salts 1 and 4 were used to form the metal ethylxanthate compounds (Me4N)[M(EtXn)x] (x=3 for M=Cd (10 Cd), Ni (10 Ni), Zn (10 Zn); x=4 for M=La (11 La)) and (Ph4P)[M(EtXn)3] (M=Cd (12 Cd), Ni (12 Ni), Zn (12 Zn)). Solubility studies on these compounds were performed using a range of solvents to demonstrate the viability of using these compounds for solution‐based deposition methods for thin‐film formation. TGA of the metal xanthate compounds was used to examine their thermal‐decomposition profiles and the product resulting from thermolysis was found to be the respective metal sulfide. In addition, the coproducts of thermal decomposition were analysed by headspace gas‐chromatography mass spectrometry (HS GC–MS) to probe the decomposition mechanism of the precursors. In situ variable‐temperature synchrotron XRD studies on both bulk and thin‐film samples of 10 Cd and 12 Cd were used to examine metal sulfide crystalline phase formation. Decomposition of both precursors was found to give CdS in a hexagonal phase, with the addition of CdCl2 found to aid in increasing the crystallite size during crystallisation.

FTIR studies of xanthate adsorption on chalcopyrite, pentlandite and pyrite surfaces

The Fourier transform infrared (FTIR) spectra of sodium butyl xanthate, dibutyl dixanthogen, metal xanthate compounds and surfaces of chalcopyrite, pentlandite and pyrite treated with sodium butyl xanthate solution were systematically studied. The products of xanthate adsorpted on the three different minerals were characterized by comparing their FTIR spectra to those of dixanthogen and metal xanthate. Both metal xanthate and dixanthogen are formed on the surfaces of these minerals. However, the relative proportions of metal xanthate to dixanthogen on the minerals are different. In the cases of chalcopyrite and pentlandite, the quantity of metal xanthate is larger than that of dixanthogen. For pyrite, on the contrary, the quantity of dixanthogen is much greater than that of ferric xanthate. Therefore, the formation of dixanthogen is more essential for the flotation of pyrite.

Characterisation and Thermal Decomposition Behaviour of Xanthate Compounds

Zinc methyl xanthate [Zn(mext)2], zinc ethyl xanthate [Zn(ext)2], zinc isopropyl xanthate [Zn(ipxt)2], zinc butyl xanthate [Zn(bxt)2], and zinc ethylene glycol xanthate [Zn(egxt)2] were prepared in the laboratory. The reaction temperature, reaction time, and yield were optimised. The thermal decomposition behaviour of these xanthates was studied using thermogravimetric analysis (TGA) and differential thermal analysis (DTA) techniques.

The role of alkyl chain length in the inhibitory effect n-alkyl xanthates on mushroom tyrosinase activities.

Sodium salts of four n-alkyl xanthate compounds, C2H5OCS2Na (I), C3H7OCS2Na (II), C4H9OCS2Na (III), and C6H13OCS2Na (IV) were synthesized and examined for inhibition of both cresolase and catecholase activities of mushroom tyrosinase (MT) in 10 mM sodium phosphate buffer, pH 6.8, at 293 K using UV spectrophotometry. 4-[(4-Methylbenzo)azo]-1,2-benzendiol (MeBACat) and 4-[(4-methylphenyl)azo]-phenol (MePAPh) were used as synthetic substrates for the enzyme for catecholase and cresolase reactions, respectively. Lineweaver-Burk plots showed different patterns of mixed, competitive or uncompetitive inhibition for the four xanthates. For the cresolase activity, I and II showed uncompetitive inhibition but III and IV showed competitive inhibition pattern. For the catecholase activity, I and II showed mixed inhibition but III and IV showed competitive inhibition. The synthesized compounds can be classified as potent inhibitors of MT due to their Ki values of 13.8, 11, 8 and 5 microM for the cresolase activity, and 1.4, 5, 13 and 25 microM for the catecholase activity for I, II, III and IV, respectively. For the catecholase activity both substrate and inhibitor can be bound to the enzyme with negative cooperativity between the binding sites (alpha > 1) and this negative cooperativity increases with increasing length of the aliphatic tail of these compounds. The length of the hydrophobic tail of the xanthates has a stronger effect on the Ki values for catecholase inhibition than for cresolase inhibition. Increasing the length of the hydrophobic tail leads to a decrease of the Ki values for cresolase inhibition and an increase of the Ki values for catecholase inhibition.

Impact of copper and lead on the activation of pyrite in the presence of thiol collectors

Lead and copper activation onto pyrite in the presence of thiol collectors was examined by means of cyclic voltammetry and micro-flotation techniques. Di-isobutyl dithiophosphinate (Aerophine 3418A) and alkyl thionocarbamate (AERO 3894) were employed as lead and copper collectors, respectively. Otherwise, isopropyl xanthate was also used as a collector of both lead and copper. The results revealed that, in the presence of non-conventional collectors, the increment in pyrite recovery owing to the activation by copper and lead species was noticeably smaller than that exhibited by the use of xanthate (IPX) under the same conditions. The electrochemical response of activated pyrite suggests the formation of copper and lead xanthate compounds and the increase in the peak could be attributed to the formation of dixanthogen. The voltammograms of pyrite stayed un-affected regardless of the activation by lead or copper.

Spectroelectrochemical investigations of the interaction of ethyl xanthate with copper, silver and gold: I. FT-Raman and NMR spectra of the xanthate compounds

Raman and 13C NMR spectroscopies have been applied to characterise the ethyl xanthate compounds of potassium, sodium, copper, silver, and gold, and diethyl dixanthogen in order to provide a basis for investigating the interaction of ethyl xanthate with metal surfaces. Spectra for the various species in the solid state obtained by both techniques are interpreted in terms of molecular conformation and differences in atomic environments in the crystal structure. Spectra for potassium ethyl xanthate in aqueous solution provide evidence of hydrophobic interaction between the hydrocarbon moiety and water. Raman spectroscopy provides an effective means of distinguishing between dixanthogen and metal xanthates.

The surface and solution chemistry of pyrite flotation with xanthate in the presence of iron ions

The effects of the surface and solution chemistry of the Fe(II) and Fe(III) ions on the flotation of both ore- and coal-pyrite with xanthate have been systematically investigated based on flotation results, zeta potential measurements and thermodynamic calculations. It was found that the presence of ferrous and ferric ions in solution significantly depresses ore-pyrite flotation in the pH range of 6–9.5. The effect of ferrous ions is stronger than that of ferric ions. Coal pyrite was found to be nonfloatable above pH 6 due to the large amounts of ferrous ions resulted from pyrite oxidation. The results of thermodynamic calculations have been found to be in good agreement with the experimental results, indicating that the formation of ferric hydroxyl xanthate compounds are responsible for the reduced floatabilities of pyrites when pH is greater than 6.

Electroluminescent ZnS:Mn films prepared at 220–450°C using complex compounds with sulphur-containing ligands

A method of preparation of manganese-doped ZnS electroluminescent films is proposed using the decomposition in vacuum of volatile complex dithiocarbamate and xanthate compounds. The composition and structure of the films were studied by chemical, electron paramagnetic resonance (EPR) and X-ray phase analyses. It was shown that the crystal structure of the films depends on the class of precursor and the presence of dopant. Using the EPR method, it was found that, at manganese concentrations of about 1% or less, the dopant is incorporated into the ZnS lattice as single non-interacting ions. The electroluminescence maximum was observed at λ = 580 nm; the luminance was about 1500 cd m −2 at a voltage of about 190 V and a frequency of 5 kHz.

Mechanisms of pyrite flotation with xanthates

Thermodynamic equilibrium calculations have been carried out for the Fe-S-X-CO 3 2−-H 2O systems, where X denotes xanthates. The results were interpreted by means of dominance and distribution diagrams to study the stability of Fe(III)-xanthate compounds under different chemical conditions. Selected electrochemical studies on the pyrite/ethyl xanthate systems are compared with the results obtained by flotation and infrared spectroscopic techniques, and are correlated with the thermodynamic studies to elucidate the mechanisms involved in the flotation of pyrite with xanthates as collectors. Contrary to previous studies, our studies show that dixanthogen is not the sole species responsible for the flotation behavior of pyrite. The thermodynamic stability studies demonstrate that insoluble Fe(III)-xanthate compounds can be formed under normal flotation conditions. The results of pyrite flotation with ethyl xanthate indicate that the formation of ferric dihydroxy ethyl xanthate on pyrite surfaces can either improve or deteriorate the floatability of pyrite, depending on the concentration of ethyl xanthate. Good flotation can be obtained when ethyl xanthate ions and/or diethyl dixanthogen are coadsorbed on ferric dihydroxy ethyl xanthate sites. Electrochemical measurements in the pyrite/ethyl xanthate systems show that the open-circuit potentials of pyrite electrodes in ethyl xanthate solutions are essentially independent of the solution pHs, and furthermore, are within the stability regions of Fe(III)-ethyl xanthate compounds. This also indicates that the pyrite surfaces may be covered by Fe(III)-ethyl xanthate compounds. FTIR spectroscopic studies confirmed the formation of Fe(III)-xanthate compounds on the pyrite surfaces. The Fe(III)-xanthate compounds are strongly bonded to the pyrite surface. Above the Fe(III)-xanthate compound layer, dixanthogens and xanthate ions are co-adsorbed probably as multiple layers.

Interference of xanthate compounds with phorbol ester TPA-induced changes of phospholipid metabolism: inhibition of prostaglandin production

Mecanisme d'action sur la lignee cellulaire HeLa, de l'inhibition de l'activite cancerigene du phorbol acetate-13, myristate-14, par MW 266 et MW 158, deux derives xanthates

Synergistic antiviral effect of xanthates and ionic detergents

Xanthate compounds have been shown to exhibit antiviral activity against various DNA and RNA viruses under acidic pH conditions. It is now possible to utilize the unique broad range antiviral spectrum of these compounds under physiological pH conditions (pH 7.4) by simultaneous administration of certain ionic detergents. When used in conjunction with tricyclodecan-9-yl-xanthate (D609), sodium deoxycholate, sodium dodecylsulfate and certain fatty acids, which have no antiviral activity of their own, inhibit the replication of various DNA and RNA viruses (such as herpes simplex, vesicular stomatitis and Coxsackie B 4) in vitro at pH 7.4. Among saturated fatty acids of various chain lengths there was a marked size restriction in that the efficiency of undecanoic acid (11 C atoms) was three orders of magnitude greater than that of shorter (6 C atoms) or longer (18 C atoms) monocarbonic acids. Dose-response kinetics revealed a synergistic interaction between the xanthate and the monocarbonic acid. A dose that inhibited the replication of herpesvirus by a factor of 1000 still permitted mitotic activity in uninfected growing control cultures.

An XPS—AES study of gaseous xanthates and related sulfur-containing compounds

Core XPS spectra for carbon, oxygen, and sulfur and KLL Auger spectra for sulfur in CH 3OCS 2CH 3, (CH 3OCS 2) 2, CS 2, and OCS have been measured and relaxation shifts determined for the sulfur atoms by combining the S 1 s measurement with the S KLL ( 1 D 2) measurement. Relaxation shifts of the sulfur atoms were also estimated from CNDO results for the neutral and core-ionized molecules using the equivalent cores approximation. The results are in qualitative agreement with the measurements, but exaggerate the relaxation by about 100%. The results show that the bonding of the (CH 3O-) group in the two xanthate compounds is very similar. The ionization energies of the S and -S- atoms within the xanthate molecules differ from each other by 1.5 eV; this difference arises almost entirely from the initial-state charge distribution rather than from final-state relaxation. However, the ionization energies of similarly bonded sulfur atoms are nearly the same. The effect of the oxygen atom on the bonding of the carbon and -S- atoms in the (-CS 2-) group in the xanthate compounds is to increase the (C 1 s-S 2 p 3 2 ) ionization energy difference from the value reported for aliphatic disulfides.

DNA and RNA virus species are inhibited by xanthates, a class of antiviral compounds with unique properties.

Various DNA and RNA virus species are inhibited by xanthate compounds at concentrations that leave the mitotic activity of uninfected cells unimpaired. The concentration of tricyclodecan -9-yl- xanthogenate that reduces the yield of herpes simplex virus types 1 and 2 by 50% is between 4.5 and 33 microM. The replication of DNA viruses such as simian virus 40 can be blocked at the DNA and RNA level both early and late after infection. The xanthates are not incorporated into nucleic acids. Episomal bovine papilloma virus DNA replication and transcription are also inhibited in transformed cells. The treated cells revert to the normal phenotype by acquisition of contact inhibition and a flat morphology.

Use of thin films in ultraviolet studies of cellulose xanthate

AbstractA procedure for the study of the chemistry of viscose based on ultraviolet measurements of a film of cellulose xanthate has been developed. To illustrate the range of usefulness of the technique, spectra of various compounds formed with cellulose xanthate, including metal salts, organic derivatives, and an acid form, the influence of solvation on several cellulose xanthate compounds, and formation and decomposition curve of cellulose xanthate derivatives are presented. Possible applications of the technique include a study of the acid decomposition of cellulose xanthate, the influence of additives, new derivatives, and the xanthation mechanism. It is also probable that the method can be used in the study of other systems where fast reaction mechanisms are involved and suitable absorption characteristics are present.