Reactions of polychlorophenyllithium compounds with electrophiles

Polychloroaromatic compounds lithiated by BuⁿLi in THF react with several electrophilic agents of which aldehydes and epoxides seem to be the most promising from the preparative point of view. Dedicated to Corresponding Member of the Russian Academy of Sciences E. P. Serebryakov on the occasion of his 70th birthday. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 941–946, April, 2005.     

Detection of traces of oxidized and reduced sulfur compounds in small samples by combination of different high-performance liquid chromatography methods

Depending on the sulfur species, picomoles of different inorganic sulfur compounds can be detected and separated by HPLC in one arrangement in a sample volume less than 50 μl. The combination of fluorescence labelling of reduced inorganic sulfur compounds such as sulfide (S²⁻), sulfite(SO₃²⁻ and thiosulfate (S₂O₃²⁻) with monobromobimane followed by an extraction of elemental sulfur (S°) by chloroform treatment enables the detection of all mentioned sulfur compounds as well as sulfate (remaining aqueous phase) in the same sample. While the derivatized sulfur compounds could be detected by their fluorescence emission at 480 nm, elemental sulfur is identified by its UV absorption at 263 nm. Sulfate in the remaining aqueous phase is detected by HPLC with indirect UV detection at 254 nm. Detection ranges for the different sulfur compounds examined are as follows: sulfide (5 μM to 1.5 mM), sulfite (5 μM to 1.0 mM), thiosulfate (1 μM to 1.5 mM), elemental sulfur (2 μM to 32 mM) and sulfate (5 μM to >1 mM).     

Comparison of methods to estimate geometric and electronic properties on sulfur containing compounds

Summary Various spectroscopic properties have been calculated by CEPA-1 for NC₃NC, a molecule of potential interest to astrochemistry. According to CCSD(T) calculations with a basis set of 168 cGTOs, it is less stable than dicyanoacyetylene (NC₄N) by 108.5 kJ mol^–1. The equilibrium dipole moment is predicted to be 1.04 D (CCSD(T)/162 cGTO), with the negative end of the dipole at the terminal nitrogen site. The results of the present calculations are in excellent agreement with those of matrix-isolation IR spectroscopy carried out in the course of this work.     

Reactions of polyfluorocarbonyl compounds and their trifluoroacetylimines with fused heterocycles

C-Hydroxy- andC-aminoalkylation of iminodibenzyl, iminostilbene, phenoxazine, and phenothiazine with hexafluoroacetone, methyl trifluoropyruvate, and their trifluoroacetylimines were investigated. The substitution occurred at one or severalpara- andortho-positions to the N atom of the heterocycles. In the case of methyl trifluoropyruvate and its derivative the substitution in theortho-position was accompanied by the formation of lactams.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1239–1242, May, 1996.     

Reactions of sulfur with organic compounds

On heating 2-thienylchloromethane or di-2-thienylsulfide with elementary sulfur in o-dichlorobenzene at 180–185°, there was obtained 1, 2-di-2-thienylethylene in yields of 10 and 19%, respectively. In contrast to stilbene, the latter on reaction with sulfur did not give tetra-2-thienylthiophene, or other low-molecular weight products. The mass, PMR, and IR spectra of 1, 2-di-2-thienylethylene were examined.For Part XX, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1183–1184, September, 1970.     

Reactions of trichloromethyl radicals with organosilicon compounds

The photolysis of carbon tetrachloride in the presence of a number of organosilicon compounds has been investigated in the gas phase. The products obtained from the photolysis experiments were those expected from a chain reaction in which trichloromethyl radicals abstract hydrogen atoms from the organosilane. Arrhenius parameters for hydrogen atom transfer were determined relative to those for trichloromethyl radical combination. The activation energies for the reaction of methyl, trifluoromethyl, and trichloromethyl radicals with organosilicon compounds are compared and the results rationalized in terms of polar effects.     

Reactions of N-phenyl-o-semiquinonediimine complexes of nickel and platinum with carbonyl-containing low-valence iron and rhenium compounds

The reactions of o-semiquinonediimine complexes M[o-(NH)(NPh)C₆H₄]₂ (M = Ni (1) or Pt (2)) with carbonyl-containing iron and rhenium compounds were studied. The reactions of complexes 1 or 2 with Fe(CO)₅ afforded the Fe₂(CO)₆[-(NH)(NPh)C₆H₄] complex (3) containing the bridging N-phenyl-o-phenylenediamide ligand in high yield. The reaction of the Re(CO)₂(NO)Cl₂(thf) complex with complex 2 gave rise to the unusual mononuclear rhenium(iii) complex, viz., Re(Ph)[-¹-o-(NH)(NHPh)C₆H₄](CO)(NO)Cl₂ (4), no changes in the geometry of N-phenyl-o-phenylenediamine bound to the Re(NO)(CO)₂Cl₂ fragment being observed. The reaction of complex 2 with the Re(CO)₅Cl complex, which has been preliminarily treated with silver triflate, afforded the heterometallic complex (CO)Pt[-N,N-o-(N)(NPh)C₆H₄]₂ReCl[(NH)(NPh)C₆H₄]. The structures of the resulting complexes were established by X-ray diffraction analysis.     

Headspace SPME followed by GC/PFPD for the analysis of malodorous sulfur compounds in liquid industrial effluents

Headspace SPME was used to analyse malodorous sulfur compounds in liquid industrial effluents. A pulsed flame photometric detector (PFPD) was selected for a specific and sensitive analysis. Two fibres, PDMS/Dvb and PDMS/Carboxen, which are particularly convenient for extracting small and volatile molecules were tested. To compare these fibres, both sensitivity and artefact formation were considered. The PDMS/Carboxen fibre showed the lower limits of detection and moreover the least artefact formation yields. It was therefore selected and headspace SPME extraction conditions were optimised. Limits of detection of the target compounds evaluated were 12–31 ng L^–1 and repeatability was around 7%. Due to the adsorption mechanism involved, extraction is strongly influenced by the sample matrix and the low affinity compounds can suffer displacement effects. To investigate the occurrence of this phenomenon, two sampling times corresponding to non-equilibrium (5 min) and equilibrium conditions (60 min) were investigated. An external calibration was carried out by using standard solutions for both sampling times. The developed procedure was then compared to the standard addition method on a real industrial effluent. The results obtained from the two methods and for the two extraction times were in good agreement, demonstrating that even a long sampling time can be used. Therefore, the simple and timesaving external calibration was defined as relevant for an accurate quantification of sulfur compounds by headspace SPME.     

Microbial reduction of sulfur dioxide with pretreated sewage sludge and elemental hydrogen as electron donors

It has been demonstrated that heat- and alkali-pretreated sewage sludge may serve as an electron donor and carbon source for SO₂ reduction byDesulfovibrio desulfuricans. A continuousD. desulfuricans culture was operated for 6 mo with complete reduction of SO₂ to H₂S. The culture required only minor amounts of mineral nutrients in addition to pretreated sewage sludge. It has also been shown that the sulfate-reducing bacteriumDesulfotomaculum orientis can be grown on H₂ as an energy source, CO₂ as a carbon source, and SO₂ as a terminal electron acceptor. Complete reduction of SO₂ to H₂S was observed.     

On-line mass spectrometric analysis of hydrothermal reactions for biomass model sample containing sulfur compounds

Biomass gasification using supercritical water is a promising way to produce hydrogen gas. However, this method might release toxic heteroatomic compounds. It is therefore important to clarify reaction pathways for efficiently obtaining hydrogen gas and suppressing environmental burden. L-cysteine was adopted for a test reagent containing sulfur and determination of the sulfur compound reaction pathways was studied by Li⁺-ion attachment mass spectrometry. It was found that H₂S, CO, CO₂, SO, SO₂ and SO₃ gasses were released at high concentrations in the gas phase during the hydrothermal reaction. By adding Ca(OH)₂ as alkali, the pathway of these gasses were, however, suppressed into the liquid phase so that the toxic emissions to the gas phase could be avoided.     

Reactions of monothiooxamides with O-methylhydroxylamine

The reactions of monothiooxamides with O-methylhydroxylamine were studied. Depending on the substituents in monothiooxamides, the reactions result in the formation of hydroxamic acid derivatives or various N-methoxy derivatives of amidoximes.     

Evaluation of desulfurization procedures for the elimination of sulfur interferences in the organotin analysis of sediments

Different clean-up and desulfurization procedures were compared in order to check their efficiency in eliminating elemental sulfur and organosulfur compounds from sediment extracts. Adsorption column chromatography cannot remove elemental sulfur or organosulfur compounds. Treatment with activated copper powder only removes elemental sulfur, but organosulfur compounds remain in the extract, and phenyltins are partially lost (up to 50%). Ligand exchange chromatography with AgNO₃-coated silica gel as adsorbent effectively removes elemental sulfur and interfering organosulfur compounds from the sediment extract allowing the quantitation of butyltins with recoveries >80%. Since the phenyltin compounds do not survive the desulfurization step, they should be measured in the untreated extract.     

Reactions of hexaorganyldigermoxanes with O-trimethylsilyl carbamates

Hexa-n-butyl- and hexaisopentyldigermoxanes but not hexaphenyldigermoxane react with O-trimethylsilyl N,N-diethylcarbamate and trimethylsilyl piperidinocarboxylate to give O-triorganylgermyl carbamates.     

Determination of the sulfur components of gasoline streams by capillary column gas chromatography with sulfur chemiluminescence detection

A method using a sulfur chemiluminescence detector (SCD) has been developed for the qualitative and quantitative determination of sulfur components in stabilized gasoline-range process streams, including blended gasolines containing between 1 and > 4000 ppm total sulfur. The detection limit per sulfur component was approximately 50 ppb. On-column injection was employed for optimum precision and accuracy. A new probe material was found which did not soften under FID operating conditions. A new method, using a hydrogen sulfide permeation tube, was developed for rapid alignment of the probe in the FID.     

Analysis ofAllium sulfur amino acids by HPLC after derivatization

Summary Two pre-column derivatization procedures coupled with reversed phase HPLC have been compared for the analysis ofS-Alk(en)yl0L-cysteine sulfoxides in variousAllium species. In order to establish external standards some (+/-) sulfoxides were synthesized, using a new method to enhance asymmetric synthesis of the diastereoisomers. The first derivatization method is the formation ofo-phthaldialdehyde/tert.-butylthiol derivatives which can be analyzed using UV detection. The second, presently used for amino acid analysis, is the Waters Pico-Tag method, which employs phenylisothiocyanate as derivatization reagent. As the Pico-Tag method was found to be the most efficient for determination ofS-alk(en)yl-L-cysteine sulfoxides it was used to determine the alliin content of various samples of garlic.     

Reactivity of electron-poor decamethyl-1,3-diboraruthenocene with sulfur and phosphorus compounds

Decamethyl-1,3-diboraruthenocene [(η⁵-C₅Me₅)Ru{η⁵-(CMe)₃(BMe)₂}] (1) reacts with cyclo-octasulfur in hexane to give [(η⁵-C₅Me₅){η⁵-(CMe)₃(BMe)₂}RuS] (3), which may also be obtained from 1 and propylene sulfide. 1 reacts with H₂S to form the ruthenathiacarboranyl complex [(η⁵-C₅Me₅)Ru{η⁴-(CMe)₃(BMe)₂S}] (6), for which a nido-structure is proposed. The isomeric compounds 3 and 6 have different stabilities: 3 loses sulfur and unexpectedly the closo-cluster [(η⁵-C₅Me₅)₂Ru₂H(CMe)₃(BMe)₂] (4) is formed with hydrogen bridging the basal and apical Ru centers. Reaction of 1 with carbonylsulfide (COS) yields the dinuclear ruthenium compound [(η⁵-C₅Me₅)Ru{η⁵-(CMe)₃(BMe)₂(S)(COBMe)}]₂ (7) in which two B-O groups bridge two ruthenium complexes. Its formation results from a complex reaction sequence: sulfur inserts into the diborolyl ring and the ligand CO forms an oxygen-boron bridge to a second molecule, followed by insertion of the carbonyl carbon into the double bond of the diboraheterocycle. Carbon disulfide reacts with 1 to give the dinuclear complex 8 with two CS₂ molecules connecting the ruthenium centers. When 1 and P₄ are heated in toluene, the sandwich 9 is obtained by formal insertion of a P-H group into the diborolyl ring of 1 and the triple-decker [{η⁵-(C₅Me₅)Ru}₂{μ-(MeC)₃P(MeB)₂} (10) is detected in the mass spectrum. The phosphaalkyne PCtBu inserts into 1 to give the ruthenaphosphacarborane [(η⁵-C₅Me₅)Ru{(CMe)₂(BMe)(PCtBu)(CMe)(BMe)}] (11) in high yield. Phosphanes react with 1 to give weak donor-acceptor complexes 1 · PH₂R (12) (R=Ph, H). The compositions of the compounds are deduced from spectroscopic and analytical data and are confirmed for 4 and 7 by X-ray structural analyses.     

Reactions of cyclic sulfur ylides with some carbonyl compounds

The reaction of a six‐membered sulfonium ylide 5 with aldehydes or ketones afforded the oxirane derivatives 6a–d as a mixture of cis and trans isomers in excellent yields. In addition, the same reactions, using five‐ or six‐membered cyclic oxosulfonium ylides 7 and 11 , gave the corresponding oxirane derivatives in good yields. Moreover, the reaction of 11 with two equimolar amounts of base and 4‐hexen‐3‐one afforded the cyclooctene oxide derivative 16 with high stereoselectivity in 59% yield via a sequential Michael–Michael‐type addition of the ylide and the resulting enolate ion followed by an intramolecular Corey–Chaykovsky reaction. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:216–222, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10022     

Addition of sulfur radicals to fullerenes

The addition of oxygen‐centered radicals to fullerenes has been intensively studied due to their role in cell protection against against hydrogen peroxide induced oxidative damage. However, the analogous reaction of sulfur‐centered radicals has been largely overlooked. Herein, we investigate the addition of S‐centered radicals to C₅₀, C₆₀, C₇₀, and C₁₀₀ fullerenes by means of DFT calculations. The radicals assayed were: S, SH, SCH₃, SCH₂CH₃, SC₆H₅, SCH₂C₆H₅, and the open‐disulfide SCH₂CH₂CH₂CH₂S. Sulfur, the most reactive species, prefers to be attached to a 66‐bond of C₆₀ with a binding energy (E_bind) of 2.4 eV. For the SR radicals the electronic binding energies to C₆₀ are 0.77, 0.74, 0.58, 0.67, and 0.35 eV for SH, SCH₃, SCH₂CH₃, SCH₂C₆H₅, and SC₆H₅, respectively. The reactivity of C₆₀ toward SR radicals can be increased by lithium doping. For Li@C₆₀, the E_bind is increased by 0.65 eV with respect to C₆₀, but only by 0.33 eV for the exohedral doping. Fullerenes act like free radical sponges. Indeed, the C₆₀‐SR E_bind can be duplicated if two radicals are added in ortho or para positions. The enhanced reactivity because of multiple additions is mostly a local effect, although the addition of one radical makes the whole cage more reactive. Therefore, as observed for hydroxylated fullerenes, they should protect cells from oxidative damage. However, the thiolated fullerenes have one advantage, they can be easily attached to gold nanoparticles. For the addition on pentagon junctions smaller fullerenes like C₅₀ are more reactive than C₆₀. Interestingly, C₇₀ is as reactive as C₆₀, even for the addition on the equatorial belt. For larger fullerenes like C₁₀₀, reactivity decreases for the carbon atoms belonging to hexagon junctions. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Coulometric determination of total sulfur and reduced inorganic sulfur fractions in environmental samples

Evaluation of the solid-phase partitioning of sulfur is frequently an important analytical component of risk assessments at hazardous waste sites because minerals containing reduced-sulfur can significantly affect the transport and fate of organic and inorganic contaminants in natural environments. We applied selected methods for the determination of total sulfur, acid-volatile sulfide (AVS), chromium-reducible sulfur (CRS), and extractable-sulfate in standard reference materials and sediment samples from a contaminated site. A coulometric titration method is presented and evaluated for total sulfur, AVS, and CRS. This method is especially advantageous for AVS and CRS determinations because hydrogen sulfide gas evolved during chemical extraction is detected and quantitated in-line; consequently, measurement endpoints can be precisely determined without need for setting arbitrary time limits. The coulometric method allows for improved data quality and increased laboratory throughput of samples. Data on sulfur partitioning are presented for four standard reference materials (NIST 1646a, NIST 2780, CCRMP LKSD-1, CCRMP RTS-3) for the purpose of supporting quality control in environmental studies involving the geochemical and biochemical cycling of sulfur.     

Reactions of 5-aryloxazolidines with CH-acidic compounds

5-Aryloxazolidines react with active methylene compounds in the presence of catalytic magnesium ethoxide to give methylene-linked 1,3-dicarbonyl compounds, while the similar reaction with 2-oxindoles results in 3-methyl derivatives.