Capillary electrophoretic separation of polycyclic aromatic sulfur heterocycles

Capillary electrophoresis (CE) was used to separate polycyclic aromatic sulfur heterocycles (PASHs), a class of compounds that occurs in fossil fuels and refined products of petroleum. An electric charge was introduced into the compounds through methylation or phenylation of the sulfur atom. Separations of standard PASHs that are expected to be present in industrially desulfurized fuels showed that CE possessed a higher resolution than reversed phase liquid chromatography. The CE method can separate all the monomethylbenzothiophenes; this is not achieved in capillary gas chromatography. A linear relationship was found between migration time and the calculated volume of the compounds. The PASHs in deeply desulfurized diesel were separated after preconcentration, and the electropherogram was compared with the chromatograms from GC and HPLC. Finally, derivatized PASHs are often enantiomeric and the enantiomers can be separated if a suitable cyclodextrin is added to the running buffer.     

Thermochemical sulfate reduction a review

The high concentrations of hydrogen sulfide found in many oil and gas fields is thought to arise from the oxidation of petroleum hydrocarbons by sulfate—a reaction that reduces the value of the resource. This review, undertaken in order to better understand the geochemistry of TSR reaction in oil field sediments, covers the relevant information on thermochemical sulfate reduction (TSR) to 1991. The theoretical and experimental aspects of TSR reactions (including sulfur and carbon isotope studies) are reviewed and their significance to the geochemical system discussed. The present review agrees with previous suggestions that biochemical reduction of sulfate dominates in sedimentary environments below 120°C, and supports the possibility that reactive sulfur species will oxidize certain organic molecules at meaningful rates in geochemically reasonable reaction periods at temperatures above 175°C. We conclude that under typical petroleum reservoir reaction conditions, both elemental sulfur and polysulfides are capable of oxidizing some organic molecules under basic conditions. But that sulfate alone will not react unless lower oxidation state sulfur is present. The possible interaction of low-valence-state sulfur with sulfate to form TSR active oxidants is examined. both H₂S and SO ₄ ²⁻ are required for the formation of active polysufide reductants (e.g. thiosulfate or polythionates) in TSR systems. Such intermediates can serve to lower the overall activation energy of the oxidation of hydrocarbons by sulfate via thermal generation of sulfur radicals that can function as TSR active oxidants in many oil field sediments. We suggest that some proposed chemical mechanisms for TSR need to be experimentally verified and the results re-interpreted with respect to TSR relations in geologic systems. Dedicated to Professor Lisa Heller-Kallai on the occasion of her 65^th birthday     

A leap forward in sulfonium salt and sulfur ylide chemistry

Sulfonium salts and sulfur ylides are important S(Ⅳ) motifs,and have displayed many unique reactivities to provide simple,effective,and often stereoselective synthesis toward sulfur containing compounds.Impressive developments have been witnessed within this field during the past several years.In light of the increasing demand of organosulfur compounds across the range of chemical sciences,our aim of this review is to provide a concise overview of recent advances of sulfonium salt and sulfur ylide chemistry.Selected examples are organized in three parts on the basis of their role in organic reactions(reactants,intermediates and catalysts).     

Selective adsorption of refractory sulfur species on active carbons and carbon based CoMo catalyst

Adsorption technique could be a reliable alternative in removing to a certain remarkable extent the sulfur species from the feedstock of petroleum oil. The performance of various carbons on adsorption of model sulfur compounds in a simulated feed solution and the sulfur containing compounds in the real gas oil was evaluated. The adsorption experiments have been carried out in a batch scale at ambient temperature and under the atmospheric pressure. In general, the most refractory sulfur compounds in the hydrotreatment reactions were selectively removed and adsorbed. It was found that the adsorbents affinities to dibenzothiophene and 4,6-dimethyldibenzothiophene were much more favored and pronounced than the aromatic matrices like fluorene, 1-methylnaphthalene and 9-methylanthracene. Among the sulfur species, 4,6-dimethyldibenzothiophene was the highest to be removed in terms of both selectivity and capacity over all the present adsorbents. The studied adsorbents showed significant capacities for the polyaromatic thiophenes. The electronic characteristics seem to play a certain role in such behavior. Regeneration of the used adsorbent was successfully attained either by washing it with toluene or by the release of the adsorbates through heat treatment. A suggested adsorptive removal process of sulfur compounds from petroleum distillate over carbon supported CoMo catalyst was discussed.     

Recent advances in reactions between arynes and organosulfur compounds

The recent progress made on transformations involving the reactions between aryne intermediates and organosulfur compounds has been reviewed. A wide variety of aromatic organosulfurs are now synthesizable by generating arynes in the presence of organosulfur compounds. Organosulfurs have distinctive reactivities with arynes, which depend on the sulfur atom’s valence state, that is, S(II), S(IV), and S(VI), as well as the presence or absence of other intra- or intermolecular reactive moieties. These novel transformations have enabled the diversity-oriented synthesis of unique aromatic organosulfurs that were once difficult to prepare by the conventional methods, paving the way for the development of molecules that are beneficial across numerous disciplines, including pharmaceutical science and materials science.     

Fragmentation pathways of some benzothiophene radical cations formed by atmospheric pressure chemical ionisation

Polycyclic aromatic sulfur‐containing compounds (PASHs) are commonly found in fossil fuels and are of considerable importance in environmental studies. This work presents detailed studies on the fragmentation patterns of radical cations formed from four representative PASHs, benzo[b]thiophene, dibenzothiophene, 4‐methyldibenzothiophene and 4,6‐dimethyldibenzothiophene, using tandem atmospheric pressure chemical ionization mass spectrometry (APCI‐MS/MS). Understanding these fragmentation patterns can be a useful aid in the analysis of PASHs employing APCI or electron ionization (EI‐MS/MS), either alone or in conjunction with liquid or gas chromatography. Copyright © 2009 John Wiley & Sons, Ltd.     

Turning the Light on Phenols: New Opportunities in Organic Synthesis

Phenols ( I ) are extremely relevant chemical functionalities in natural, synthetic and industrial chemistry. Their corresponding electron-rich anions, namely phenolates ( I ), are characterized by interesting physicochemical properties that can be drastically altered upon light excitation. Specifically, phenolates ( I ) become strong reducing agents in the excited state and are able to generate reactive radicals from suitable precursors via single-electron transfer processes. Thus, these species can photochemically trigger strategic bond-forming reactions, including their direct aromatic C−H functionalization. Moreover, substituted phenolate anions can act as photocatalysts to enable synthetically useful organic transformations. An alternative mechanistic manifold is represented by the ability of phenolate derivatives I to form ground state electron donor-acceptor (EDA) complexes with electron-poor radical sources. These complementary scenarios have paved the way for the development of a wide range of relevant organic reactions. In this Minireview, we present the main examples of this research field, and give insight on emerging trends in phenols photocatalysis towards richer organic synthesis.     

渣油超临界萃取馏分中硫化物的分离富集研究

采用选择性氧化与色谱结合的方法分离渣油中的硫醚硫化物和噻吩硫化物,该法是基于不同类型硫的选择性氧化、氧化组分与未氧化组分间极性的差异实现的。首先用高碘酸四丁铵在不氧化噻吩硫的情况下将硫醚硫选择性氧化为高极性的亚砜,经色谱柱分离富集后,利用红外色谱和硫元素分析仪,研究了馏分中硫化物的类型分布。结果表明,在俄罗斯渣油中噻吩硫和硫醚硫的质量分数随组分变重均呈增长趋势,噻吩硫相对质量分数(指硫醚硫+噻吩硫)随馏分变重呈下降趋势,相对质量分数在70%以上,噻吩硫是俄罗斯渣油中硫的主要存在形态。     

Role of sulfur chirality in the chemical processes of biology

Chiral structures profoundly influence chemical and biological processes. While chiral carbon biomolecules have received much attention, chirality is also possible in certain sulfur compounds; just as with carbon, there can be differences in the physiological behavior of chiral sulfur compounds. For instance, one drug enantiomer, Nexium (esomeprazole, a chiral sulfoxide), is used for its superior clinical properties as a proton pump inhibitor over the racemic mixture, Prilosec (Losec, omeprazole). This critical review introduces sulfur stereochemistry and nomenclature, and provides a comprehensive approach to chiral sulfur compounds and their enzymatic reactions in general and secondary metabolism. The major structural types of biological interest are sulfonium salts, sulfoxides, and sulfoximines. (103 references).     

Determination of polycyclic aromatic sulfur heterocycles in diesel particulate matter and diesel fuel by gas chromatography with atomic emission detection

The sulfur content of diesel fuel is of environmental concern because sulfur can facilitate the formation of diesel particulate matter (DPM) and sulfur dioxide (SO2) in the exhaust can poison catalytic converters. The US Environmental Protection Agency (EPA) has established more stringent regulations to reduce the sulfur content of diesel fuels in the near future. In this study, various types of organosulfur compounds in DPM extracts and the corresponding fuels have been determined by gas chromatography with atomic emission detection. The diesel fuels used have sulfur contents of 2284 and 433 ppm, respectively, and are labeled as high-sulfur and low-sulfur diesel fuels. The compounds identified are mainly polycyclic aromatic sulfur heterocycles (PASHs). In the fuels tested, trimethylbenzothiophenes (TMBTs), dibenzothiophenes (DBTs), and 4-methyldibenzothiophene (4-MDBT) were the most abundant sulfur compounds, while larger PASH compounds were more abundant in DPM extracts. The high-sulfur diesel fuel contained a larger proportion of PASHs with one or two rings (lighter PASHs). In DPM, the concentrations of total organic sulfur and individual PASHs are higher for the high-sulfur diesel fuel, and the relative percentage of one or two-ring PASHs is higher as well. The influence of engine load on the DPM composition was also examined. With increasing load, the PASH concentration in DPM decreased for lighter PASHs, increased for heavier PASHs, and had a bell-shaped distribution for PASHs in between.     

Synthesis of Organometallic Compounds in Flow

Microreactor technology has proved to be an important technique in organic synthesis, especially when organometallic compounds are used, because it allows running rapid reactions with reactive and instable intermediates. This review will highlight the preparation of main‐group organometallic compounds deriving from Lithium, Magnesium, Zinc and Aluminum and their applications in flow conditions.     

Dibenzo[b,f]oxepin‐10(11H)‐one and dibenzo[b,f]thiepin‐10(11H)‐one as useful synthons in the synthesis of various dibenzo[e,h]azulenes

The present review focuses on dibenzo[b,f]oxepin‐10(11H)‐one ( I , X = O) and dibenzo[b,f]thiepin‐10(11H)‐one ( I , X = S) as common synthons in the efficient synthesis of various dibenzoxepino[4,5‐ and dibenzothiepino[4,5]‐fused five‐membered heterocycles: [2,3] fused thiophene ( II ), [3,4] fused thiophene ( III ), furan ( IV ), pyrrole ( V ), imidazole ( VI ), pyrazole ( VII ), oxazole ( VIII ), and thiazole ( IX ). The potential of I to be converted into reactive intermediates that readily undergo heteroaromatic annulation reactions by cyclocondensation with proper binucleophiles allows formation of a range of enumerated functionalized dibenzo[e,h]azulene [4] structures ( II , III , IV , V , VI , VII , VIII , IX ). Dibenzo[e,h]azulenes as heterotetracyclic scaffold can be exploited in further modifications to obtain compounds with altered physicochemical and biological profile. J. Heterocyclic Chem., (2012).     

Carbenes,related intermediates,and small-sized cycles: contribution from Professor Nefedov’s laboratory

The review summarizes some of the most prominent results obtained in the laboratory headed by Academician Oleg M. Nefedov at the N. D. Zelinsky Institute of Organic Chemistry of the Russian Academy of Sciences in the field of chemistry of carbenes, their heavy analogs, and related intermediates, as well as small-sized cycles. Those include elaboration of safe methodology of cyclopropanation using diazomethane, development and extension of synthetic applications of diazoesters and other diazo compounds in the preparation of valuable chemical products, design of functionalized alkynylcyclopropanes on the basis of alkynylcarbene reactions, creation of versatile synthetic approaches to preparation of various practically useful fluoroorganic compounds on the basis of reactions of fluorocarbenes, development of synthetic applications of heavy carbene analogs and synthesis of small-sized heterocycles containing silicon and germanium atoms, analysis of mechanisms of some important reactions of carbenes, their analogs and related intermediates on the basis of physicochemical studies, direct spectroscopic studies of various labile intermediates of chemical reactions.     

Catalysts on the basis of anion-modified metal oxides for production of ecologically pure components of motor fuels

Experimental evidence on the production, structure, and physiochemical properties of aluminum, zirconium, and titanium oxides modified with halides, sulfates, and boron and tungsten oxides. Information on the application of anion-modified metal oxides as catalysts in the production of ecologically pure components of motor fuels, with decreased contents of aromatic hydrocarbons and sulfur compounds. Therewith, along with traditional hydrocarbon oligomerization, isomerization, alkylation reactions, actual arene hydroisomerization processes and production of diesel fuels from vegetable materials are considered.     

Hydrophilic Conjugated Materials for Photocatalytic Hydrogen Evolution

Photocatalytic hydrogen evolution is viewed as a promising green strategy to utilize the inexhaustible solar energy and provide clean hydrogen fuels with zero‐emission characteristic. The nature of semiconductor‐based photocatalysts is the key point to achieve efficient photocatalytic hydrogen evolution. Conjugated materials have been recently emerging as a novel class of photocatalysts for hydrogen evolution and photocatalytic reactions due to their electronic properties can be well controlled via tailor‐made chemical structures. Hydrophilic conjugated materials, a subgroup of conjugated materials, possess multiple advantages for photocatalytic applications, thus spurring remarkable progress on both material realm and photocatalytic applications. This minireview aims to provide a brief review of the recent developments of hydrophilic conjugated polymers/small molecules for photocatalytic applications, and special concern on the rational molecular design and their impact on photocatalytic performance will be reviewed. Perspectives on the hydrophilic conjugated materials and challenges to their applications in the photocatalytic field are also presented.     

Oxidation‐Induced C—H Functionalization: A Formal Way for C—H Activation

Cross‐coupling reactions have developed widely and provided a powerful means to synthesize a variety of compounds in each chemical field. The compounds which have C—H bonds are widespread in fossil fuels, chemical raw materials, biologically active molecules, etc. Using these readily‐ available substances as substrates is high atom‐ and step‐economy for cross‐coupling reactions. Over the past decades, our research group focused on finding and developing new strategies for C—H functionalization. Compared with classical C—H activation methods, for example, C—H bonds are deprotonated by strong base or converted into C—M bonds, oxidation‐induced C—H functionalization would be another pathway for C—H bond activation. This perspective shows a brief introduction of our recent works in this oxidation‐induced C—H functionalization. We categorized this approach of these C—H bond activations by the key intermediates, radical cations, radicals and cations.     

Intermediate detection in real time using reactive surface desorption dielectric‐barrier discharge ionization mass spectrometry

Reactive intermediates play key roles for reaction mechanism elucidation. A suitable tool for identifying the key intermediates is crucial and highly desirable. In this study, surface desorption dielectric‐barrier discharge ionization (reactive SDDBDI) was developed for characterization of the reactive intermediates. In reactive SDDBDI, the plasma is doped with a reagent before the plasma ions are directed at a cover slip surface bearing another analyte. Different from SDDBDI, reactive SDDBDI can be used both as an ambient ionization source and as a means to produce reagent ions for ambient ion/molecule reactions. The online derivation of 4‐aminophenol with trifluoroacetic anhydride demonstrated that reactive SDDBDI can be used for chemical analysis where improved specificity or sensitivity is required. The utility of this approach for real‐time detection of reactive intermediate was demonstrated by the Schiff‐base and Eberlin reactions. The formed intermediates and products could be readily detected and identified by tandem mass spectrometry. These results indicate that reactive SDDBDI can be used to generate reagent ions that undergo ion/molecule reactions in the open air with an analyte at condensed phase on a surface. Reactive SDDBDI has high‐efficiency ion transmission and high MS sensitivity. It is thus a potential tool to perform ambient ion/molecule reactions and detect reactive intermediates.     

Interactions of thiophenes with C300 Basolite MOF in solution by the temperature-programmed adsorption and desorption,spectroscopy and simulations

Aromatic sulfur compounds, e.g. thiophene (T), benzothiophene (BT), dibenzothiophene (DBT), 4,6-dimethyldibenzothiophene (4,6-DMDBT) are present in petroleum and fossil fuels, and cause air pollution, degradation of catalytic converters, deactivation of fuel-reforming catalysts. In this paper, we report kinetic, thermodynamic, spectroscopic and computational studies of adsorption of T, BT, DBT, and 4,6-DMDBT from solution in n-alkane on metal–organic framework (MOF) Basolite C300 at 25–115 °C. The novel temperature-programmed adsorption/desorption method allows the in situ measurement of an adsorption capacity at the variable temperature, and after the cycle “adsorption/desorption”. Adsorption of BT, DBT and 4,6-DMDBT at 25 °C occurs via the formation of the stoichiometric 1:1 adsorption complexes. BT adsorbs reversibly, while 4,6-DMDBT adsorbs irreversibly. The formation of the adsorption complex of the aromatic sulfur compound with MOF is confirmed by the fluorescence spectroscopy for the first time. The DFT computations of the geometry and energy of dispersive versus electronic interactions of T and DBT with the structural units of the C300 MOF are reported for the first time. The mechanism of adsorption is proposed as a combination of dispersive and electronic interactions of the aromatic sulfur compounds with BTC linker and Cu(II) CUS of C300 MOF.     

Atmospheric organic aerosol production by heterogeneous acid-catalyzed reactions.

Exploratory evidence from our laboratories shows that acidic surfaces on atmospheric aerosols lead to very real and potentially multifold increases in secondary organic aerosol (SOA) mass and build-up of stabilized nonvolatile organic matter as particles age. One possible explanation for these heterogeneous processes are the acid-catalyzed (e.g., H2SO4 and HNO3) reactions of atmospheric multifunctional organic species (e.g., multifunctional carbonyl compounds) that are accommodated onto the particle phase from the gas phase. Volatile organic hydrocarbons (VOCs) from biogenic sources (e.g., terpenoids) and anthropogenic sources (aromatics) are significant precursors for multifunctional organic species. The sulfur content of fossil fuels, which is released into the atmosphere as SO2, results in the formation of secondary inorganic acidic aerosols or indigenous acidic soot particles (e.g., diesel soot). The predominance of SOAs contributing to PM2.5 (particulate matter, that is, 2.5 microm or smaller than 2.5 microm), and the prevalence of sulfur in fossil fuels suggests that interactions between these sources could be considerable. This study outlines a systematic approach for exploring the fundamental chemistry of these particle-phase heterogeneous reactions. If acid-catalyzed heterogeneous reactions of SOA products are included in next-generation models, the predicted SOA formation will be much greater and have a much larger impact on climate-forcing effects than we now predict. The combined study of both organic and inorganic acids will also enable greater understanding of the adverse health effects in biological pulmonary organs exposed to particles.