Sulfur Derivatives Research Articles

Electrochemical Oxidation of Dibenzothiophene in Acetonitrile and Acetonitrile-Water Mixtures

Crude oil is basically formed of a mixture of many hydrocarbons containing a wide variety of heteroatoms like sulfur and nitrogen. The content of sulfur in crude oil can vary from 0.05% to 10% [1]. This percentage is low; however, this amount is particularly important due to environmental implications [2, 3]. The major sulfur compounds present in crude oil are thiophenes, benzothiophenes, dibenzothiophenes, which are carcinogens. For that reason, the hydrodesulfurization [4], which is the method used in refineries, does not remove all the sulfur compounds, mainly dibenzothiophene and derivatives. To reach this objective, several methods have been proposed to remove the sulfur compounds by converting them into hydrogen sulfide or more polar compounds [5]. For that reason, it has been of interest to explore the electro-oxidative behavior of these compounds to convert them to more polar compounds that are easier to extract with water as solvent [6]. It is known that refractory organosulphur compounds such as dibenzothiophene (DBT) can be oxidized to dibenzothiophenesulfoxide (DBTO) and dibenzothiophenesulfone (DBTO2), that can be removed by physical methods such as extraction and adsorption using polar solvents. Therefore, in this work the electrochemical oxidation of a model sulfur aromatic compound such as dibenzotiophene (DBT) was studied in acetonitrile in the presence of low ( < 0.1 M ) and high ( > 1 M) content of water on carbon electrodes. This study is focused to obtain mechanistic information about the products formed. Cyclic voltammetry of DBT in acetonitrile in the presence of < 0.1 M water on glassy carbon electrode showed three chemically irreversible anodic peaks. The first and second peaks involve a global transfer of one electron which allows respectively the formation of sulfoxide and sulfone derivatives as well as the release of one equivalent of protons, according to the global proposed reaction. DBT – e- + H2O = DBTO + H+ + 1/2H2 When water was added to the acetonitrile solution ( >1 M ), the voltammetric pattern was maintained, however the global mechanism giving rise to the sulfoxide and sulfone derivatives was modified to two electrons with the release of two equivalents of protons. DBT – 2e- + H2O = DBTO + 2H+ The proton formation was confirmed by cyclic voltammetry using acetate ions as proton probe while the products dibenzothiophene sulfoxide and dibenzothiophene sulfone were prepared by constant potential electrolysis and characterized by HPLC-MS-TOF and 1H and 13C NMR experiments. The analysis of the variation of the peak potential and half-peak width with the scan rate was used to establish the relevant role of water on the reaction mechanism, which changes from an ECCCC to an ECCEC pathway when water is present in excess According to the above mentioned results, different oxidation products can be formed depending on the electrolysis conditions and for this reason, this work deals with the anodic oxidation process of DBT in acetonitrile to determine how the intermediates and the composition of the electrolyte solution govern the formation of the oxygenated products. Cyclic voltammetry, sampled current chronoamperometry, coulometry, preparative electrolysis, chromatography coupled with mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy were used as analytical techniques Acknowledgements The authors acknowledge CONACYT for financial support through the project 221548. E.M.A also acknowledges B.R. Díaz and G. Cuellar for their assistance in some electrochemical, NMR and MS analysis respectively.

Extreme variation of sulfur isotopic compositions in pyrite from the Qiuling sediment-hosted gold deposit, West Qinling orogen, central China: an in situ SIMS study with implications for the source of sulfur

High spatial resolution textural (scanning electron microscope (SEM)), chemical (electron microprobe (EMP)) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS)), and sulfur isotopic (secondary ion mass spectrometry (SIMS)) analyses of pyrite from the Qiuling sediment-hosted gold deposit (232 ± 4 Ma) in the West Qinling orogen, central China were conducted to distinguish pyrite types and gain insights into the source and evolution of sulfur in hydrothermal fluids. The results reveal an enormous variation (−27.1 to +69.6 ‰) in sulfur isotopic composition of pyrite deposited during three paragenetic stages. Pre-ore framboidal pyrite, which is characterized by low concentrations of As, Au, Cu, Co, and Ni, has negative δ34S values of −27.1 to −7.6 ‰ that are interpreted in terms of bacterial reduction of marine sulfate during sedimentation and diagenesis of the Paleozoic carbonate and clastic sequences, the predominant lithologies in the deposit area, and the most important hosts of many sediment-hosted gold deposits throughout the West Qinling orogen. The ore-stage hydrothermal pyrite contains high concentrations of Au, As, Cu, Sb, Tl, and Bi and has a relatively narrow range of positive δ34S values ranging from +8.1 to +15.2 ‰. The sulfur isotope data are comparable to those of ore pyrite from many Triassic orogenic gold deposits and Paleozoic sedimentary exhalative (SEDEX) Pb-Zn deposits in the West Qinling orogen, both being hosted mainly in the Devonian sequence. This similarity indicates that sulfur, responsible for the auriferous pyrite at Qiuling, was largely derived from the metamorphic devolatization of Paleozoic marine sedimentary rocks. Post-ore-stage pyrite, which is significantly enriched in Co and Ni but depleted in Au and As, has unusually high δ34S values ranging from +37.4 to +69.6 ‰, that are interpreted to result from thermochemical reduction of evaporite sulfates in underlying Cambrian sedimentary rocks with very high δ34S values. The variations in Au content and sulfur isotopic compositions across a single ore-stage pyrite grain may reflect displacement of indigenous groundwater with low δ34S values by auriferous metamorphic fluids with high δ34S values. The very low-grade metamorphism of the host rocks and the metamorphic derivation of sulfur for the ore pyrite indicate that the Qiuling sediment-hosted gold deposit is an epizonal manifestation of an orogenic gold system in the West Qinling orogen.

Facile Synthesis of 2,4-Disubstituted Thiooxazoles and 2,4-Disubstituted Oxazole Sulfonyl Chlorides via Acyl Isothiocyanates and TMS-Diazomethane

An expedient method for the direct conversion of acyl isothiocyanates to 2,4-disubstitued thiooxazoles and 2,4-disubstituted oxazole sulfonyl chlorides is described. The method takes advantage of an early observation by Sheehan and the reaction of diazomethane with isocyanates to form oxazolones. However, in this case an acyl isothiocyanate is utilized as well as the readily available TMS-diazomethane to provide access to the desired 4-substituted sulfur derivatives. The 2,4-disubstituted oxazole systems synthesized represent novel thiooxazoles and oxazole sulfonyl chlorides not previously described.

A mitochondria-targeted ratiometric fluorescent probe to monitor endogenously generated sulfur dioxide derivatives in living cells

Sulfur dioxide (SO2) can be endogenously produced by enzymes in mitochondria during oxidation of H2S or sulphur-containing amino acids, and plays important roles in several physiological processes. However, the design and synthesis of fluorescent probes which can detect mitochondrial SO2 and its derivatives in living cells still remain unresolved. Herein, we report the preparation of a lipophilic cationic dye 1 (Mito-Ratio-SO2), which targets the mitochondria in living cells and is sensitive to the presence of SO2 derivatives. The ratiometric probe Mito-Ratio-SO2 displays a 170 nm blue-shift in emission with two well-resolved emission bands upon addition of sulfite. Mechanistic studies indicate that three probe-SO2 adducts coexist after reaction, as supported by liquid chromatography and density function theory investigations. Importantly, the ratiometric probe is highly selective for sulfite over other bio-species including H2S. Fluorescence co-localization studies indicate that the probe localizes solely in the mitochondria of HeLa cells. Last but not least, fluorescent imaging of HeLa cells successfully demonstrates the detection of intrinsically generated intracellular SO2 derivatives in living cells.

Electron ionization mass spectral studies of phenoxide derivatives of mustards: Implications for analysis to support chemical weapons convention

Mass spectrometric (MS) analytical features of phenoxide derivatives of sulfur and nitrogen mustards were described. Electron ionization (EI) mass spectra of title chemicals with possible fragmentation routes were investigated via analysis of fragment ions of deuterated analogs, MS–MS experiments and density functional theory calculations. EI-MS and EI-MS/MS analysis revealed phenoxide, ethane, CO, CS and H2S exclusions, α-cleavages, retro Diels–Alder cycloaddition, hydrogen rearrangements and a previously unknown intramolecular Claisen-type rearrangement. The results would be valuable during toxic chemical destruction monitoring in support of chemical weapons convention (CWC) and for the verification of state-parties activities, based on CWC context.

Semi-synthesis of new antimicrobial esters from the natural oleanolic and maslinic acids

In this article, we report an effective procedure for the selective isolation of oleanolic acid 1 and maslinic acid 2 (3.4 and 8.5mg/g DW, respectively) from pomace olive (Olea europaea L.) using an ultrasonic bath, and the synthesis of a series of new triterpenic acid esters. The compounds were characterized by their spectral data and were evaluated for their antimicrobial activity. Among the compounds tested, those having sulfur and chlorine atoms were found to be antibacterial. They showed activity against two Gram-positive bacteria Staphylococcus aureus and Enterococcus faecalis and two Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa (MICs within a range of 5–25μg/mL). The fungus Penicillium italicum was found to be the most sensitive to both sulfur derivatives: (3β)-3-((thiophene-2-carbonyl)oxy)-olean-12-en-28-oic acid (1a) (IZ=22mm) and (2α,3β-2,3-bis((thiophene-2-carbonyl)oxy)olean-12-en-28-oic acid (2a) (IZ=24mm).

Sulfur Derivatives of the Natural Polyarsenical Arsenicin A: Biologically Active, Organometallic Arsenic–Sulfur Cages Related to the Minerals Realgar and Uzonite

(±)-Arsenicin A (AsA), (±)-1, the first natural polyarsenical to be isolated, has the adamantane-type structure of the mineral arsenolite (As4O6), in which three of the oxygen atoms have been replaced by methylene groups to give an organometallic, arsenic–oxygen cage of C2 symmetry. Heating of a benzene solution of AsA with aqueous sodium sulfide produces, by reductive desulfurization of the intermediate sulfur analog (±)-2, the monosulfide cage (±)-4, which contains two As–As bonds and which has a C2-chiral cage structure related to the mineral realgar (α-As4S4). At room temperature the reaction affords a chiral disulfide derivative that exists as a pair of separable diastereomers, (±)-3a and (±)-3b, each of which contains a single As–As bond and is structurally related to the mineral uzonite (As4S5). The crystal structures of the monosulfide (±)-4 and the diastereomeric disulfides (±)-3a and (±)-3b have been determined. As for AsA, the sulfur derivatives exhibit strong UV absorptions and can be resolved on a Chiralpak IA column. The monosulfur cage (±)-4 is considerably more potent and more selective than AsA and the current “arsenical gold standard”, arsenic(III) oxide as Trisenox, against the acute promelocytic leukemia cells (NB4) and certain solid cancer cell lines.

FTIR micro‐reflectance absorption spectroscopic analysis of chemisorbed reaction films for tribological applications

AbstractChemisorbed reaction films (CRFs) were prepared by using iron (Fe) particles (100–200 mess size) and thio (sulfur) derivatives of ethyl octadecenoate and methyl 12‐hydroxy octadecenoate in the light viscosity paraffin liquid medium. The reaction was conducted in a simulated condition of tribo‐chemical situation. CRFs were obtained in solid amorphous phase. The CRFs were examined for elemental composition and layer analysis using C‐H‐N‐O‐S analyzer and Fourier transform infrared spectroscopy micro‐reflectance absorption spectroscopic technique. Further, the CRFs were isolated into organic solvent soluble fractions using polar solvents of increasing polar strength. Their elemental analyses were studied, and chemical constitutions were known. Friction coefficient and wear scar diameter were evaluated by high frequency reciprocating rig, PLINT TE‐77 machine. Thermal stability was studied using thermogravimetric analysis technique in nitrogen environment. These studies inferred that CRFs appeared varying in its composition, luster, phase, chemical structure and thermal stability. Nonetheless, these were also found anomalous in elemental distribution throughout the layer structure of the CRFs. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Synthetic approaches for sulfur derivatives containing 1,2,4-triazine moiety: their activity for in vitro screening towards two human cancer cell lines.

A series of sulfur 1,2,4-triazine derivatives were prepared and evaluated as anticancer compounds for two human breast cancer cell lines (MCF-7, MDA-MB-231) with some of them acting as low micromolar inhibitors. Evaluation of the cytotoxicity using a 3-(4,5-dimethylthiazol-2-yl)-3,5-diphenyltetrazolium bromide (MTT) assay, the inhibition of [(3)H]thymidine incorporation into DNA, and collagen synthesis inhibition demonstrated that these products exhibit cytotoxic effects on these breast cancer cell lines in vitro. The most effective were disulfide and sulfenamide compounds with two valence sulfur atoms. A structure-activity relationship study was performed using X-ray analysis and theoretical calculations at an ab initio density functional theory (DFT) level.

Structural Elucidation of Sulfur Derivatives of Benzimidazoles by Density Functional Calculations, and Vibrational and NMR Spectral Analyses

The room temperature structural as well as vibrational (IR and Raman) and NMR (1H and 13C) spectral studies have been performed on 1-methyl-benzimidazole-2-thione, 2-(methylthio)benzimidazole, and 1-methyl-2- mercaptobenzimidazole tautomers at B3LYP/6-311++G** level of theory. 1-methyl-benzimidazole-2-thione is the most stable tautomer with significant energetic separations than the other two tautomers and with too high transition barriers to the other tautomers. This suggests that 1-methyl-benzimidazole-2-thione is the main species at the room temperature. Comparison of experimental and calculated room temperature vibrational and NMR spectra suggests the presence of the 2-(methylthio)benzimidazole and 1-methyl-2-mercaptobenzimidazole tautomers in the solid and solution phases as minor species.

Regenerable antioxidants-introduction of chalcogen substituents into tocopherols.

To improve the radical-trapping capacity of the natural antioxidants, alkylthio-, alkylseleno-, and alkyltelluro groups were introduced into all vacant aromatic positions in β-, γ- and δ-tocopherol. Reaction of the tocopherols with electrophilic chalcogen reagents generated by persulfate oxidation of dialkyl dichalcogenides provided convenient but low-yielding access to many sulfur and selenium derivatives, but failed in the case of tellurium. An approach based on lithiation of the appropriate bromo-tocopherol, insertion of chalcogen into the carbon-lithium bond, air-oxidation to a dichalcogenide, and final borohydride reduction/alkylation turned out to be generally applicable to the synthesis of all chalcogen derivatives. Whereas alkylthio- and alkylseleno analogues were generally poorer quenchers of lipid peroxyl radicals than the corresponding parents, all tellurium compounds showed a substantially improved radical-trapping activity. Introduction of alkyltelluro groups into the tocopherol scaffold also caused a dramatic increase in the regenerability of the antioxidant. In a two-phase lipid peroxidation system containing N-acetylcysteine as a water-soluble co-antioxidant the inhibition time was up to six-fold higher than that recorded for the natural antioxidants.

Selective, highly sensitive fluorescent probe for the detection of sulfur dioxide derivatives in aqueous and biological environments.

On the basis of a unique nucleophilic addition reaction, a novel water-soluble broadly emitting (500-700 nm) fluorescent Probe 1 was developed for the rapid detection of SO2 derivatives in aqueous media. The positively-charged benzopyrylium moiety in Probe 1 provides both excellent water solubility, making this probe applicable in 100% aqueous environments, and the ability to function as a fluorescence quencher of the coumarin moiety. Probe 1 generates a nearly instantaneous strong fluorescence signal in response to SO2 derivatives having an 8.3 nM detection limit for bisufite. The resulting Probe 1-sulfite adduct emits in the green/red spectral region (λ(max) = 585 nm) with a large Stokes shift (139 nm). The probe exhibits excellent selectivity toward SO2 derivatives over other potential interfering agents including reactive sulfur-containing species. Importantly, we demonstrate that Probe 1 can be used for the real-time sensing and bioimaging of SO2 derivatives in living cells.

Synthetic, Structural, and Spectroscopic Studies of Sterically Crowded Tin–Chalcogen Acenaphthenes

A series of sterically encumbered peri-substituted acenaphthenes have been prepared containing chalcogen and tin moieties at the close 5,6-positions (Acenap[SnPh3][ER], Acenap = acenaphthene-5,6-diyl, ER = SPh (1), SePh (2), TePh (3), SEt (4); Acenap[SnPh2Cl][EPh], E = S (5), Se (6); Acenap[SnBu2Cl][ER], ER = SPh(7), SePh (8), SEt (9)). Two geminally bis(peri-substituted) derivatives ({Acenap[SPh2]}2SnX2, X = Cl (10), Ph (11)) have also been prepared, along with the bromo–sulfur derivative Acenap(Br)(SEt) (15). All 11 chalcogen–tin compounds align a Sn–CPh/Sn–Cl bond along the mean acenaphthene plane and position a chalcogen lone pair in close proximity to the electropositive tin center, promoting the formation of a weakly attractive intramolecular donor–acceptor E···Sn–CPh/E···Sn–Cl 3c-4e type interaction. The extent of E→Sn bonding was investigated by X-ray crystallography and solution-state NMR and was found to be more prevalent in triorganotin chlorides 5–9 in comparison with triphenyltin derivatives 1–4. The increased Lewis acidity of the tin center resulting from coordination of a highly electronegative chlorine atom was found to greatly enhance the lp(E)−σ*(Sn–Y) donor–acceptor 3c-4e type interaction, with substantially shorter E–Sn peri distances observed in the solid state for triorganotin chlorides 5–9 (∼75% ∑rvdW) and significant 1J(119Sn,77Se) spin–spin coupling constants (SSCCs) observed for 6 (163 Hz) and 8 (143 Hz) in comparison to that for the triphenyltin derivative 2 (68 Hz). Similar observations were observed for geminally bis(peri-substituted) derivatives 10 and 11.

Synthesis and structure of sulfur derivatives from 2-aminobenzimidazole.

The reactions of the benzimidazole nitrogen atoms and the exocyclic amino group of 2-aminobenzimidazole with CS2 in NaOH basic medium followed by methylation with methyl iodide was explored. With careful control of the stoichiometric quantities and addition sequences, this set of reactions allows the selective functionalization of the benzimidazole ring with N-dithiocarbamate, S-methyldithiocarbamate or dimethyl- dithiocarboimidate groups. The products were characterized by 1H-, 13C-NMR spectroscopy and three of them by X-ray diffraction analysis. The preferred isomers, tautomers and conformers were established.

Synthesis and cytotoxicity of allobetulin derivatives

The synthesis and screening of antitumor activity in vitro (cytotoxicity) of various oxygen, nitrogen, sulfur and platinum-containing derivatives of allobetulin, including different arrangements of the double bonds in the A and B rings, penta- and hexacyclic ring A, 21-acetyl-20,28-epoxy-18α,19βH-ursane-isomeric cycle E, was carry out. (3R,5R)-19β,28-Epoxy-4,5-seco-18α-olean-3(5)-ozonide and 2,3-indolo-21β-acetyl-20β,28-epoxy-18α, H-19β-ursane showed significant cytotoxic activity against melanoma MeWo and Leukemia SR cells, appropriately. (3S,5S)-Diastereomer of the first compound showed no cytotoxicity.

Geology and fluid characteristics of the Ulu Sokor gold deposit, Kelantan, Malaysia: Implications for ore genesis and classification of the deposit

The Ulu Sokor gold deposit is one of the most famous and largest gold deposits in Malaysia and is located in the Central Gold Belt. This deposit consists of three major orebodies that are related to NS- and NE-striking fractures within fault zones in Permian-Triassic meta-sedimentary and volcanic rocks of the East Malaya Block. The faulting events represent different episodes that are related to each orebody and are correlated well with the mineralogy and paragenesis. The gold mineralization consists of quartz-dominant vein systems with sulfides and carbonates. The hydrothermal alteration and mineralization occurred during three stages that were characterized by (I) silicification and brecciation; (II) carbonatization, sericitization, and chloritization; and (III) quartz–carbonate veins.Fluid inclusions in the hydrothermal quartz and calcite of the three stages were studied. The primary CO2–CH4–H2O–NaCl fluid inclusions in stage I are mostly related to gold mineralization and display homogenization temperatures of 269–389°C, salinities of 2.77–11.89wt.% NaCl equivalent, variable CO2 contents (typically 5–29mol%), and up to 15mol% CH4. In stage II, gold was deposited at 235–398°C from a CO2±CH4–H2O–NaCl fluid with a salinity of 0.83–9.28wt.% NaCl equivalent, variable CO2 contents (typically 5–63mol%), and up to 4mol% CH4. The δ18OH2O and δD values of the ore-forming fluids from the stage II quartz veins are 4.5 to 4.8‰ and −44 to −42‰, respectively, and indicate a metamorphic–hydrothermal origin. Oxygen fugacities calculated for the entire range of T-P-XCO2 conditions yielded log fO2 values between −28.95 and −36.73 for stage I and between −28.32 and −39.18 for stage II. These values indicate reduced conditions for these fluids, which are consistent with the mineral paragenesis, fluid inclusion compositions, and isotope values.The presence of daughter mineral-bearing aqueous inclusions is interpreted to be a magmatic signature of stage IIIa. Combined with the oxygen and hydrogen isotopic compositions (δ18OH2O=6.8 to 11.9‰, δD=−77 to −62‰), these inclusions indicate that the initial fluid was likely derived from a magmatic source. In stage IIIb, the gold was deposited at 263° to 347°C from a CO2–CH4–H2O–NaCl fluid with a salinity of 5.33 to 11.05wt.% NaCl equivalent, variable CO2 contents (typically 9–15mol%), and little CH4. The oxygen and hydrogen isotopic compositions of this fluid (δ18OH2O=8.1 to 8.8‰, δD=−44 to −32‰) indicate that it was mainly derived from a metamorphic–hydrothermal source. The CO2–H2O±CH4–NaCl fluids that were responsible for gold deposition in the stage IIIc veins had a wide range of temperatures (214–483°C), salinities of 1.02 to 21.34wt.% NaCl equivalent, variable CO2 contents (typically 4–53mol%), and up to 7mol% CH4. The oxygen and hydrogen isotopic compositions (δ18OH2O=8.5 to 9.8‰, δD=−70 to −58‰) were probably acquired at the site of deposition by mixing of the metamorphic–hydrothermal fluid with deep-seated magmatic water and then evolved by degassing at the site of deposition during mineralization. The log fO2 values from −28.26 to −35.51 also indicate reduced conditions for this fluid in stage IIIc. Moreover, this fluid had a near-neutral pH and δ34S values of H2S of −2.32 to 0.83‰, which may reflect the derivation of sulfur from the subducted oceanic lithospheric materials.The three orebodies represent different gold transportation and precipitation models, and the conditions of ore formation are related to distinct events of hydrothermal alteration and gold mineralization. The gold mineralization of the Ulu Sokor deposit occurred in response to complex and concurrent processes involving fluid immiscibility, fluid–rock reactions, and fluid mixing. However, fluid immiscibility was the most important mechanism for gold deposition and occurred in these orebodies, which have corresponding fluid properties, structural controls, geologic characteristics, tectonic settings, and origins of the ore-forming matter. These characteristics of the Ulu Sokor deposit are consistent with its classification as an orogenic gold deposit, while some of the veins are genetically related to intrusions.

Steam and gas emission rate from La Soufriere volcano, Guadeloupe (Lesser Antilles): Implications for the magmatic supply during degassing unrest

Since its last magmatic eruption in 1530AD, La Soufrière andesitic volcano in Guadeloupe has displayed intense hydrothermal activity and six phreatic eruptive crises. Here we report on the first direct quantification of gas plume emissions from its summit vents, which gradually intensified during the past 20years. Gas fluxes were determined in March 2006 and March 2012 by measuring the horizontal and vertical distributions of volcanic gas concentrations in the air-diluted plume and scaling to the speed of plume transport. Fluxes in 2006 combine real-time measurements of volcanic H2S concentrations and plume parameters with the composition of the hot (108.5°C) fumarolic fluid at exit. Fluxes in 2012 result from MultiGAS analysis of H2S, H2O, CO2, SO2 and H2 concentrations, combined with thermal imaging of the plume geometry and dynamics. Measurements were not only focused on the most active South crater (SC) vent, but also targeted Tarissan crater and other reactivating vents. We first demonstrate that all vents are fed by a common H2O-rich (97–98mol%) fluid end-member, emitted almost unmodified at SC but affected by secondary shallow alterations at other vents. Daily fluxes in 2012 averaged 200tons of H2O, 15tons of CO2, ~4tons of H2S and 1ton of HCl, increased by a factor ~3 compared to 2006. Even though modest, such fluxes make La Soufrière the second most important volcanic gas emitter in the Lesser Antilles arc, after Soufriere Hills of Montserrat. Taking account of other hydrothermal manifestations (hot springs and diffuse soil degassing), the summit fumarolic activity is shown to contribute most of the bulk volatile and heat budget of the volcano. The hydrothermal heat output (8MW) exceeds by orders of magnitude the contemporaneous seismic energy release. Isotopic evidences support that La Soufrière hydrothermal emissions are sustained by a variable but continuous heat and gas supply from a magma reservoir confined at 6–7km depth. By using petro-geochemical data for La Soufrière magma(s) and their dissolved volatile content, and assuming a magmatic derivation of sulfur, we estimate that the volcanic gas fluxes measured in 2012 could result from the underground release of magmatic gas exsolved from ~1400m3d−1 of basaltic melt feeding the system at depth. We recommend that fumarolic gas flux at La Soufrière becomes regularly measured in the future in order to carefully monitor the temporal evolution of that magmatic supply.

DFT study of sulfur derivatives of cumulenes and their protonated forms of interstellar interest and calculations of dissociation energies of protonated forms (SC(CH)C(n-2)S)(+) (n = 3-8).

A theoretical study of the sulfur cumulenes SCnS (n = 3-8), CnS ( n = 1-8) and of their protonated forms (SCnS)H(+) and (CnS)H(+) that might exist in the interstellar environment, has been carried out by means of the standard B3LYP/6-311G** method. The geometries and relative energies of singlet and triplet states according to the number of carbons have been computed. Like neutral species, we have found that the ground state of the most stable protonated forms (SC(CH)Cn-2S)(+) and ((HC)Cn-1S)(+), alternates between a triplet state for the even series and a singlet state for the odd series. We provided the data needed to simulate infrared and microwave spectra (vibration frequencies, dipole moments, and rotational constants) for each protonated species (SCnS)H(+) and (CnS)H(+) and for each neutral CnS species. The computing of dissociation energies of the most stable protonated forms (SC(CH)Cn-2S)(+) (n = 3-8) has shown that the lowest values are obtained for the dissociation of compounds with an even number of carbons, in their triplet state, which produce the observed fragments CS and C3S. The dissociation of even protonated forms requires less energy than for the odd protonated forms.

Functionalisation of Imidazolin-2-imine to Corresponding Phosphinamine, Chalcogenide (O, S, Se, Te), and Borane Compounds

1,3-Di-tert-butyl-imidazolin-2-ylidine-1,1-diphenylphosphinamine (2) was prepared from 1,3-di-tert-butyl-imidazolin-2-imine (1) and chlorodiphenylphosphine. Compound 2 was treated further with elemental sulfur, selenium, and tellurium to afford the corresponding chalcogenide derivatives, 1,3-di-tert-butyl-imidazolin-2-ylidine-P,P-diphenyl-phosphinothioicamide (4), 1,3-di-tert-butyl-imidazolin-2-ylidine-P,P-diphenyl-phosphinoselenoicamide (5), and 1,3-di-tert-butyl-imidazolin-2-ylidine-P,P-diphenyl-phosphinotelluroicamide (6) in good yield. 1,3-Di-tert-butyl-imidazolin-2-ylidine-P,P-diphenylphosphinicamide (3) was obtained by dissolving compound 2 in hydrochloric acid solution in THF. The corresponding borane adduct, 1,3-di-tert-butyl-imidazolin-2-ylidine-P,P-diphenyl-phosphinaminoborane (7) was isolated by the reaction of compound 2 and sodium borohydride in good yield. The molecular structures of compounds 2 and 4–7 were established by X-ray diffraction analyses. To analyse the electronic structure of chalcogenides of imidazolin-2-imine ligands, the protonation energies of the oxygen, sulfur, and selenide derivative of ligand 2 were calculated by means of density functional theory. Finally, the charge distribution in compounds 3, 4, and 5 were determined using natural bond orbital analysis.

Comparative study on intestinal metabolism and absorption in vivo of ginsenosides in sulphur‐fumigated and non‐fumigated ginseng by ultra performance liquid chromatography quadruple time‐of‐flight mass spectrometry based chemical profiling approach

Our previous study indicated that sulphur-fumigation of ginseng in post-harvest handling processes could induce chemical transformation of ginsenosides to generate multiple ginsenoside sulphur derivatives. In this study, the influence of sulphur-fumigation on intestinal metabolism and absorption in vivo of ginsenosides in ginseng was sequentially studied. The intestinal metabolic and absorbed profiles of ginsenosides in rats after intra-gastric (i.g.) administration of sulphur-fumigated ginseng (SFG) and non-fumigated ginseng (NFG) were comparatively characterized by a newly established ultra performance liquid chromatography quadruple time-of-flight mass spectrometry (UPLC-QTOF-MS/MS) with electrospray ionization negative (ESI-) mode. A novel strategy based on the characteristic product ions and fragmentation pathways of different types of aglycones (saponin skeletons) and glycosyl moieties was proposed and successfully applied to rapid structural identification of ginsenoside sulphur derivatives and relevant metabolites. In total, 18 ginsenoside sulphur derivatives and 26 ginsenoside sulphur derivative metabolites in the faeces together with six ginsenoside sulphur derivatives in the plasma were identified in the SFG-administrated group but not in the NFG-administrated group. The results clearly demonstrated that the intestinal metabolic and absorbed profiles of ginsenosides in sulphur-fumigated and non-fumigated ginseng were quite different, which inspired that sulphur-fumigation of ginseng should not be recommended before the bioactivity and toxicity of the ginsenoside sulphur derivatives were systematically evaluated.