Sulfur Functional Groups Research Articles

Ambident effect of a p-sulfinyl group for the introduction of two carbon substituents to phenol rings: a convergent synthesis of diverse benzofuran neolignans.

A convergent synthesis of diversely substituted benzofuran neolignans (8) is described employing a single p-sulfinyl group on the phenols (3) as an ambident functional group for two types of carbon-carbon bond-forming reactions: (i) the direct synthesis of the dihydrobenzofuran skeletons through an aromatic Pummerer-type reaction and (ii) the ipso-substitution of the sulfur functional group by carbon substituents through a ligand exchange reaction.

Synthesis of new synthons for organofluorine compounds from halothane containing sulfur functional groups.

To develop new synthons for the syntheses of organofluorine compounds, the treatment of Halothane, 2-bromo-2-chloro-1,1,1-trifluoroethane, (1) with 4-methylbenzenethiol (2) in the presence of sodium hydride gave 1-chloro-2,2,2-trifluoroethyl 4-methylphenyl sulfide (3), which was oxidized with m-chloroperbenzoic acid (m-CPBA) to the corresponding sulfoxide (4) and sulfone (5). Reaction of 3 and 5 with allyltributyltin in the presence of 2,2'-azobis(isobutyronitrile) (AIBN) gave 1-(trifluoromethyl)-3-butenyl compounds (9, 11). Sulfoxide 4 was decomposed in this condition. The treatment of 3 with allyltrimethylsilane in the presence of Lewis acids gave 1-(trifluoromethyl)-3-butenyl compounds (9) in good yield. This result suggests that 4-methylphenylthio substituent stabilizes the alpha-carbocation effectively, though the trifluoromethyl group destabilizes it strongly. Aromatic compounds similarly reacted with 3 in the presence of titanium(IV) chloride to give 2-aryl-1,1,1-trifluoro-2-(4-methylphenylthio)ethanes. Thus, sulfur compounds derived from Halothane were found to be useful new synthons for organofluorine compounds.

ToF-SIMS and XPS study of sulphur on carbon black surface

A very broad range of carbon blacks (CB) from different origins and different manufacturing processes (furnace CB, plasma CB, acetylene CB, plasma-treated CB, etc.) were analysed by surface-sensitive techniques: time-of-flight secondary ion mass spectrometry (ToF-SIMS) and x-ray photoelectron spectroscopy (XPS), The data were compared with conventional bulk properties of industrial CB: specific surface area and sulphur titration. Different types of sulphur functional groups were identified at CB surfaces by ToF-SIMS (HS-, SOx-, HSOx-, SCN-, etc.). A linear relationship between the ToF-SIMS intensity of the sulphur-containing ions and the total sulphur bulk quantity was observed. The total intensity of ToF-SIMS spectra was found to be dependent on the specific surface area of the CB samples. The total quantity of sulphur measured by XPS, when detected, was in good agreement with the total sulphur bulk quantity. However, the ToF-SIMS sensitivity for sulphur functional groups was much higher than the XPS sensitivity, Copyright (C) 2000 John Wiley & Sons, Ltd.

Sulphur group analysis in solid matrices by atmospheric pressure-temperature programmed reduction

The atmospheric pressure-temperature programmed reduction (AP-TPR) has become an established and reliable method amongst the different sulphur characterisation techniques for solid materials, like coal and coal derived products, rubber and clay. The analytical method is based upon the fact that specific sulphur functional groups are hydrogenated at specific temperatures. During the last few years, several adjustments have been made to the hard- and software as well as to the experimental parameters. The changes and the reliability of the method are extensively discussed in this paper.

Promoter action of sulphur on the stabilization of pitch spheres

Elemental sulphur was added into the starting pitch during the preparation of pitch-based spherical activated carbon in order to enhance the stabilization of pitch sphere. Pitch sphere (diameter 0.65–1.0 mm) without adding sulphur needs slow heating rate of 0.5 °C/min, high final temperature of 300 °C and long holding time of 20 h for the successful stabilization in air. While adding elemental sulphur with 2.5–10.0 wt % in total amount into starting pitch decreased the stabilization time significantly, pitch sphere containing 5.0 wt % of sulphur can be stabilized in air very easily at heating rate of 2.0 °C/min up to 270 °C without any holding time, and the successful stabilization time was only 3 h. Pitch molecules reacted with sulphur and some sulphur functional groups, such as C−SH, C−S−C, C=S, O=S=, O=S=O etc., were formed besides the oxygen functional groups under the stabilization condition. All of these sulphur functional groups acted as bridge bonds to make the pitch molecules polymerized so as to high up the softening point of pitch spheres, making the pitch spheres stabilized. Three kinds of sulfocompounds, i.e. H2S, COS and CS2 evolved in stabilization process.

せん断流動場反応制御技術によるゴムの連続再生 （第４報） ＥＰＤＭにおける脱硫反応メカニズム

Mechanism of devulcanization by shear flow stage reaction control technology for sulfur vulcanized EPDM rubber has been studied based on network structure of devulcanized rubber and behavior of crosslinking bond breakage. Sulfur crosslinking bonds of vulcanized rubber are broken selectively during the devulcanization reaction. There are three types of crosslinking bonds such as monosulfide, disulfide and polysulfide bond. At the initial stage of reaction, polysulfide and disulfide bonds are changed to monosulfide bond by heat. Furthermore, monosulfide bond is broken by addition of shear stress and devulcanized rubber is obtained finally. Residual sulfur atom at the broken crosslinking bonds are stabilized by reaction of adjacent hydrogen atom and change into less reactive sulfur functional groups.

X-ray Absorption Spectroscopic Evidence for the Complexation of Hg(II) by Reduced Sulfur in Soil Humic Substances

Analysis of Hg(II) complexed by a soil humic acid (HA) using synchrotron-based X-ray absorption spectroscopy (XAS) revealed the importance of reduces sulfur functional groups (thiol (R-SH) and disulfide (R-SS-R)/disulfane (R-SSH)) in humic substances in the complexation of Hg(II). A two-coordinate binding environment with one oxygen atom and one sulfur atom at distances of 2.02 and 2.38 {angstrom}, respectively, was found in the first coordination shell of Hg(II) complexed by humic acid. Model calculations show that a second coordination sphere could contain one carbon atom and a second sulfur atom at 2.78 and 2.93 {angstrom}, respectively. This suggests that in addition to thiol S, disulfide/disulfane S may be involved with the complexation of Hg(II) in soil organic matter. The appearance of carbon atom in the second coordination shell suggests that one O-containing ligand such as carboxyl and phenol ligands rather than H{sub 2}O molecule is bound to the Hg(II). The involvement of oxygen ligand in addition to the reduced S ligands in the complexation of Hg(II) is due to the low density of reduced S ligands in humic substances. The XAS results from this experiment provided direct molecular level evidence for the preference of reduced S functional groups over oxygen ligandsmore » by Hg(II) in the complexation with humic substances.« less

Ambient temperature removal rate constants for singlet methylene with some nitrogen and sulphur compounds

AbstractThe technique of laser flash photolysis/laser absorption has been used to obtain absolute removal rate constants for singlet methylene, 1CH2 (ā A1), with some nitrogen and sulphur compounds at ambient temperature (298±2 K). A measurement of the removal rate constant for 1CH2 with NH3 yielded a value of (3.33±0.19)xl0−10 cm3 molecule−1 s−1 in good agreement with the only previously reported measurement. Removal rate constants for the reactants CH3NO2, CH3CH2NO2, CH3CH2CH2NO2, CH3CN, CH3CH2CH2CN, CH2=CHCN, H2S, CH3CH2SH, CH3SCH3, CH3SSCH3, and CH3COSH were measured for the first time and found to be (3.23±0.28), (3.46±0.69), (3.55±1.28), (4.51±0.21), (3.64±0.41), (4.10±0.26), (3.87±0.22), (4.77±0.25), (4.53±0.23), (5.37±0.53), and (4.59±0.32)x10−10 cm3 molecule−1 s−1 respectively. The calculated removal efficiencies (removal rate constant relative to the Lennard‐Jones collision rate constant) are indicative of reaction being the dominant process leading to loss of 1CH2. Comparisons are drawn between the reactivities of the nitrogen and sulphur functional groups and their hydrocarbon analogues, and between the sulphur compounds and their isoelectronic oxygen analogues.

Calixarenes in electroanalysis

The use of calix[n]arenes as recognition reagents in electroanalysis is reviewed. Calix[n]arenes (n = 4 to 14) are macrocylic phenol-formaldehyde condensates which may be derivatized at the phenolic oxygen position to produce macrocycles capable of the selective binding of metal cations. Calix[4]arene derivatives having ester, ketone and amide functionality generally exhibit sodium selectivity and the larger calix[6]arenes show a preference for cesium ions. A number of calixarenes have been successfully incorporated into polymeric membrane ion-selective electrodes (including ISFETs). Calixarene-based sodium selective ISEs exhibit excellent sensitivity and selectivity, especially over potassium ions, which has allowed usage of these ISEs in assays of sodium in blood and serum. Calixarene-based ISEs sensitive to potassium, cesium and organic amine ions have also been reported. More recently ISEs and ISFETs sensitive to heavy metal ions such as silver, lead and copper(II) have been fabricated from various sulfur functional group derivatized calix[4]arenes. Potentiometric analytical uses of calixarenes have received most interest to date. However, voltammetric investigations have shown that carbon paste modified electrodes may be prepared with polymeric calixarenes and allow stripping voltammetric determination of lead, copper and mercury simultaneously. Voltammetric studies of calixquinone/hydroquinone and calixarene inclusion complexes have also been reported. Prospects for the future development of calixarenes as ionophoric reagents in electroanalysis are discussed.

Synthesis of New Chiral Building Blocks via an Enzymatic Reaction : A New Method of Enhancing Enantioselectivity of the Enzymatic Reaction

This review describes efficient means of preparing optically pure compounds via bakers' yeast mediated reaction or lipase-catalyzed reaction : (1) Bakers' yeast mediated reaction of cyanoketone was demonstrated and was discovered a new type of C-C bond forming reaction. (2) Hydrolysis of 2-substituted-3-acetoxy esters by Aspergillus lipase (lipase A 6) was demonstrated. According to summarize the stereo favoritism between substrates, the active site model of an Aspergillus lipase is proposed. (3) A simple preparation of optically active α- or γ-hydroxystannanes using Pseudomonas lipase (lipase PS) was realized. (4) Two effective means were discovered for enantioselective reaction of lipase PS : one is the modification of the acyl group by a sulfur functional group and the other is addition of a catalytic amount of l-methioninol or crown ether derivatives to the reaction mixture. (5) Optically pure (R) -4-hydroxy-3- (3, 4-methylenedioxyphenyl) methylbutanenitrile, obtained by this reaction, was applied to the synthesis of three anti-tumor lignans. (6) As a new chiral building block for tertiary alcohols, (R) -2-ally1-2- (phenylthio) methyloxirane was synthesized via lipase-catalyzed reaction.

Reversing the Regiochemical Course of 1,3-Dipolar Cycloaddition of Nitrile oxides by Modification of Dipolarophiles

The orientation of the cycloaddition of nitrile oxide to β-substituted-α,β-unsaturated aldehyde equivalents was directed by choice of the carbonyl protective group, both of the two possible regioisomers of 2-isoxazolines were selectively prepared. Cycloaddition to the acetal derivatives preferentially gave the regioisomer bearing acetal group on C(4) position. While the opposite regioselectivity was observed for the cycloaddition to dithioacetal derivatives, where the sulfur functional group was mainly located at C(5) position. Theoretical studies on these regiochemical courses showed the C(5) orientation of dithioacetal groups to be directed by steric control, whereas frontier orbital interaction controlled the C(4) orientation of the acetal groups.

ChemInform Abstract: Synthesis of Flavins Bearing a Sulfur Functional Group and Their Catalytic Activities for Reduction of Disulfides.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis of flavins bearing a sulfur functional group and their catalytic activities for reduction of disulfides

AbstractBis‐flavins, each of which bears a disulfide linkage in the molecule, have been synthesized as model compounds for dihydronicotinamide dependent disulfide reductase. These flavins were found to be much better catalysts to promote the reduction of dibenzyl disulfide to α‐toluenethiol than 3‐methyllumiflavin.

13C CP/MAS n.m.r. study of changes in molecular mobility of a bituminous coal during desulphurization

A bituminous coal has been treated with molten alkali at several reaction temperatures and for different lengths of time. The fate of pyrite and the organic sulphur functional groups during desulphurization was followed by the recently developed technique of temperature programmed reduction. From 13C CP/MAS n.m.r. it is clear that there is a good correlation between the obtained structural parameters, carbon aromaticity and the fraction of the non-protonated aromatic fraction, and the relaxation times T 2 ∗ 1H. The increased mobility in the aromatic structures confirms that the organic matrix is strongly modified when a high sulphur reduction is obtained.

In situ x-ray absorption fine structure spectroscopy investigation of sulfur functional groups in coal during pyrolysis and oxidation

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTIn situ x-ray absorption fine structure spectroscopy investigation of sulfur functional groups in coal during pyrolysis and oxidationM. Mehdi Taghiei, Frank E. Huggins, Naresh Shah, and Gerald P. HuffmanCite this: Energy Fuels 1992, 6, 3, 293–300Publication Date (Print):May 1, 1992Publication History Published online1 May 2002Published inissue 1 May 1992https://doi.org/10.1021/ef00033a009RIGHTS & PERMISSIONSArticle Views411Altmetric-Citations63LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (4 MB) Get e-Alerts Get e-Alerts

Automated potentiometric determination of sulfur functional groups in fossil fuels

Automated potentiometric determination of sulfur functional groups in fossil fuels

An investigation into the changes of structure and reactivity during desulphurization of a bituminous coal

A bituminous coal has been treated with molten (non-aqueous) caustic using several reaction temperatures and times. The caustic treatment removed all the pyritic sulphur and up to 80% of the organic sulphur. The extent of organic sulphur removed, as determined directly by scanning electron microscopy and energy-dispersive X-ray analysis (SEM-EDX), was linearly dependent on temperature. Optimal desulphurization conditions were investigated and correlated with losses in calorific value. The fate of pyrite and the organic sulphur functional groups during the desulphurization procedure was followed by the recently developed technique of temperature programmed reduction (TPR). Pyrite and the thermally labile sulphur compounds were removed, and with increasing desulphurization temperatures and times the thiophenic compounds were also removed. It has also been possible to follow the desulphurization quantitatively with TPR, i.e. the amount of aliphatic sulphur removed as indicated by the elemental analysis was the same as the amount obtained from the integrated TPR signals. These results underline the value of the TPR method as a technique for following sulphur functional group distribution during coal processing. The effect of the caustic treatment on the microstructure was clearly noticeable on the SEM micrographs showing the formation of depressions and microfissures and fragmentation into smaller particles. At higher reaction temperatures solid state 13C cross-polarization and magic angle spinning nuclear magnetic resonance ( 13C CP/MAS) indicated an increased carbon aromaticity ( f C a ) and an increase of the non-protonated aromatic fraction ( f NP a ).

Enhanced enantioselectivity of an enzymatic reaction by the sulfur functional group. A simple preparation of optically active .beta.-hydroxy nitriles using a lipase

Enhanced enantioselectivity of an enzymatic reaction by the sulfur functional group. A simple preparation of optically active .beta.-hydroxy nitriles using a lipase

ChemInform Abstract: Stereorecognition Enhancement by the Sulfur Functional Group in the Lipase Hydrolysis. An Efficient Synthesis of the Optically Active β‐Hydroxy Nitriles (R)‐(II).

ChemInform Abstract: Stereorecognition Enhancement by the Sulfur Functional Group in the Lipase Hydrolysis. An Efficient Synthesis of the Optically Active β‐Hydroxy Nitriles (R)‐(II).

SUPERCRITICAL EXTRACTION AND DESULPHURIZATION OF BEYPAZARI LIGNITE BY ETHYL ALCOHOL/NaOH TREATMENT 3. ELECTROCHEMICAL CHARACTERIZATION OF ORGANIC SULPHUR COMPOUNDS

ABSTRACT The overall objective, of this study is to develop an electrochemical method, that will be complementary to the existing spectroscopic methods, for the characterization of sulphur compounds in coal extracts. Beypazan lignite was used in this study. Supercritical interaction between coal and ethyl alcohol/NaOH (or Ca(OH2) ) was carried out using a microreactor of 15 ml capacity. Liquid products obtained were separated by liquid chromatography in a glass column have been determined and these provided a ground for the identification of various sulphur functional groups in coal liquids obtained from supercritical interaction between a lignite and ethyl alcohol/NaOH or ethyl alcohol/Ca(OH) 2 or ethyl alcohol. Organic sulphur compounds determined by this method were dibenzydisulphide, dibenzothiophene and tiophenol