Amending cultures of selenium-resistant bacteria with dimethyl selenone

A possible biological intermediate in the reduction and methylation of selenium oxyanions, dimethyl selenone, was synthesized, and the first experiments involving the amendment of selenium resistant bacterial cultures with this compound are reported. The amount of volatile, reduced selenium-containing species released from these cultures into the headspace is significantly more than that produced in analogous experiments involving sodium selenate amended cultures. Dimethyl selenone is reduced in the presence of dimethyl sulfide and dimethyl disulfide in a complex growth medium, trypticase soy broth with 0.1% nitrate. This reduction occurs whether or not the reduced sulfur compounds are biologically produced.     

Quantum-chemical interpretation of the difference in the field fragmentation of the molecular ions of dimethyl ether and dimethyl sulfide

The potential energy surfaces (PES) of the positive molecular ions of dimethyl ether and dimethyl sulfide were scanned by the LCAO-MO SCF method in the MINDO/3 valence approximation. On the PES of these radical-cations, apart from the minima corresponding to the equilbrium structures, each has a local minimum which belongs to a cyclic structure. The discovered differences in the stereochemical construction of the cyclic structures of the radical-cations (CH₃)₂O⁺'and (CH₃)₂S⁺' made it possible to explain features of the field fragmentation of their molecular ions. The effect of the external electric field of the ion source on the cyclization and fragmentation stages in the investigated radical-cations was traced.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 1, pp. 76–82, January–February, 1989.     

Molecular-field splitting in S2p photoelectron spectra of dimethyl sulfide and sulfur dichloride

High-resolution S2p photoelectron spectra have been measured for sulfur dichloride and dimethyl sulfide. By means of efficient fitting procedures and theoretical analyses, the vibrational fine structure has been disentangled from the molecular-field induced splitting of the S2p_3/2 core-ionized level. The resulting molecular-field splitting is determined to be 177 meV in the case of SCl₂ and 104 meV for (CH₃)₂S. Ab initio calculations that include core–valence electron correlation are able to reproduce these values to within 3 meV. Theoretical predictions of the molecular-field splitting are presented for a series of related sulfur compounds, SX₂, where X=H, NH₂, CN, and F.     

Molecular complexes of dimethyl sulfoxide with tri‐ and dichloromethane

Crystals of molecular complexes of dimethyl sulfoxide with trichloromethane (chloroform), (CH₃)₂SO·2CHCl₃, (I), and dichloromethane, (CH₃)₂SO·CH₂Cl₂, (II), have been grown in situ. In both compounds, the components are linked together by (Cl)C—H...O interactions. The dimethyl sulfoxide molecules in (I) are bound into chains by C—H...O interactions. In (II), pairs of the components form centrosymmetric rings, linked into a three‐dimensional network by C—H...O contacts and dipole–dipole interactions between dimethyl sulfoxide molecules.     

Studies of the naturally occurring biomethylation of selenium and the determination of the products

A systematic study of the biomethylation of selenium and the determination of the methylated species indicates preliminarily that selenium is susceptible to natural biomethylation under certain environmental conditions. Detectable levels of methylated selenium species, including dimethyl selenide [(CH₃)₂Se], dimethyl diselenide [(CH₃)₂Se₂] and dimethylselenone [(CH₃)₂SeO₂] have been detected by gas chromatography – graphite furnace atomic absorption spectrophotometry (GC – GF AA) from a variety of environmental samples. Findings of naturally methylated selenium species from both soil samples and related air samples suggest that there may exist a localized cycle of selenium between ground soil and the ambient air. Factors that influence the sensitivity and accuracy for the determination of alkyl selenide compounds by GC – GF AA have also been investigated. Flashlike injection mode and addition of about 10% of hydrogen gas to the argon carrier gas provide for highly sensitive detection. Reproducible determination can be obtained with a precision of about 6% and the detection limits are 0.3 ng Se m^?3.     

The rotational barrier in dimethyl acetylene and related molecules

The rotational barriers in dimethyl acetylene (CH₃CCCH₃), diamino acetylene (H₂NCCNH₂), dihydroxy acetylene (HOCCOH), methyl trifluoro methyl acetylene (CF₃CCCH₃), silyl methyl acetylene (SiH₃CCH₃), propene, cis and trans 2-butene and ethane were studied by ab initio molecular orbital methods using various basis sets. The eclipsed structure for dimethyl acetylene and its CF₃ and SiH₃ analogs was found to be the most stable, as has been inferred from experimental work, and the barrier height for these compounds has been predicted. The barriers in the OH and NH₂ substituted acetylenes, propene, butene and ethane were studied in order to more clearly understand the important influences in determining the barrier mechanism; specifically, the delocalized molecular orbital and Pauling VB model have been compared.     

FT‐IR kinetic and product study of the Br‐initiated oxidation of dimethyl sulfide

An FT‐IR kinetic and product study of the Br‐atom‐initiated oxidation of dimethyl sulfide (DMS) has been performed in a large‐volume reaction chamber at 298 K and 1000‐mbar total pressure as a function of the bath gas composition (N₂ + O₂). In the kinetic investigations using the relative kinetic method, considerable scatter was observed between individual determinations of the rate coefficient, suggesting the possibility of interference from secondary chemistry in the reaction system involving dimethyl sulfoxide (DMSO) formation. Despite the experimental difficulties, an overall bimolecular rate coefficient for the reaction of Br atoms with DMS under atmospheric conditions at 298 K of ≤1 × 10⁻¹³ cm³ molecule⁻¹ s⁻¹ can be deduced. The major sulfur products observed included SO₂, CH₃SBr, and DMSO. The kinetic observations in combination with the product studies under the conditions employed are consistent with rapid addition of Br atoms to DMS forming an adduct that mainly re‐forms reactants but can also decompose unimolecularly to form CH₃SBr and CH₃ radicals. The observed formation of DMSO is attributed to reactions of BrO radicals with DMS rather than reaction of the Br–DMS adduct with O₂ as has been previously speculated and is thought to be responsible for the variability of the measured rate coefficient. The reaction CH₃O₂ + Br → BrO + CH₃O is postulated as the source of BrO radicals. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 883–893, 1999     

Temperature-dependent kinetics of the simplest Criegee intermediate reaction with dimethyl sulfoxide

Criegee intermediates are thought to play roles in atmospheric chemistry, including OH radical formation, oxidation of SO₂, NO₂, etc. CH₂OO is the simplest Criegee intermediate, of which the reactivity has been a hot topic. Here we investigated the kinetics of CH₂OO reaction with dimethyl sulfoxide (DMSO) under 278–349 K and 10–150 Torr. DMSO is an important species formed in the oxidation of dimethyl sulfide in the biogenic sulfur cycle. The concentration of CH₂OO was monitored in real-time via its mid-infrared absorption band at about 1,286 cm⁻¹ (Q branch of the ν₄ band) with a high-resolution quantum cascade laser spectrometer. The 298 K bimolecular rate coefficient was determined to be k₂₉₈ = (2.3 ± 0.3) × 10⁻¹² cm³/s at 30 Torr with an Arrhenius activation energy of −3.9 ± 0.2 kcal/mol and a weak pressure dependence for pressures higher than 30 Torr (k₂₉₈ = (2.8 ± 0.3) × 10⁻¹² cm³/s at 100 Torr). The reaction is speculated to undergo a five-membered ring intermediate, analogous to that of CH₂OO with SO₂. The negative activation energy indicates that the rate-determining transition state is submerged. The magnitude of the reaction rate coefficient lies in between those of CH₂OO reactions with (CH₃)₂CO and with SO₂.     

Formation pathways of CH3SOH from CH3S(OH)CH3 in the presence of O2: a theoretical study

Methane sulfenic acid (CH₃SOH, MSEA) has been suggested in the literature as a possible stable product within the addition channel of the OH-initiated oxidation of dimethyl sulfide. In particular, it has been proposed as one of the thermodynamically feasible products of the reaction of CH₃S(OH)CH₃ adduct with O₂. However, MSEA has never been experimentally observed and a detailed theoretical analysis of all the reaction pathways leading to MSEA formation has never been reported. In this study, the first density functional and ab initio electronic structure calculations are carried out to characterize those reaction channels yielding MSEA. The adduct formed by the reaction of DMS-OH with O₂ (CH₃S(O₂)(OH)CH₃) has been taken as the starting point. On the other hand, a new reaction pathway, which competes with the MSEA formation yielding DMSO instead, is also presented. The kinetic relevance of those different reaction pathways is discussed to assert their contribution to the experimental measurements of the end-products of DMS-OH-initiated oxidation.     

Reactions of triads Se8KOHDMSO,Se8KOHDMSO,TeKOHHMPA with acetylenes

A new general approach to anionic transformations of acetylenes using superbasic media has been developed. It allows series of new reactions which are not undergone by acetylene under conventional conditions. The triads Se₈KOHdimethylsulfoxide (DMSO), Se₈KOHDMSO, TeKOH-hexamethyl-phosphorictriamide (HMPA) are proposed as new effective reagents for the preparation of unsaturated compounds of sulfur, selenium and tellerium. A series of reactions of acetylene with sulfur, selenium and tellerium proceeding in DMSO or HMPA in the presence of alkali and water at 80–120° leading to divinyl sulfide, divinyl selenide and divinyl teluride in 25–80% yields have been found. Thiophen, di-1-(1,3-butadienyl) sulfide, 1-vinyl-2-thiabicyclo[3.2.0]hept-3-ene, and dihydrothiophen have been obtained by the reaction of vinylacetate with sulfur. The reaction of vinylacetylene with selenium affords selenophen, di-1-(1,3-butadienyl) selenide, 1-vinyl-2-selenabicyclo[3.2.0]hept-3-ene, methyl (1-(1,3-butadienyl) sulfide, and methylthiomethyl 1-(1,4-butadienyl) selenide, vinyl 1-(1,3-butadienyl) sulfide, and methylthiomethyl 1-(1,3-butadienyl) selenide (the latter two with DMSO participation). The reaction of vinylacetate with tellerium gives mainly di-1-(1,3-butadienyl) telluride. A series of reactions between DMSO and selenium leading to dimethyl sulfide, dimethyl sulfoselenide, and methylthiomethyl selenide have been observed.     

Thermolysis of dimethyl sulfoxide

The thermal decomposition of dimethyl sulfoxide at small extent of reaction has been studied at temperatures of 297-350°C and pressures of 10–400 Torr. The major products CH₄, C₂H₄, and SO₂ were shown to follow first-order kinetics. The activation energies for production of each was about 48 kcal·mole^?1. A chain mechanism has been postulated in the light of the results of isotopic substitution experiments.     

An absolute and relative rate study of the reaction of oh radicals with dimethyl sulfide

The gas phase reaction of OH radicals with dimethyl sulfide (CH₃SCH₃, DMS) has been studied using both an absolute and a relative technique at 295 ± 2 K and a total pressure of 1 atm. The absolute rate technique of pulse radiolysis combined with kinetic spectroscopy was applied. Using this technique a rate constant of (3.5 ± 0.2) × 10^?12 cm³ molecule^?1 s^?1 was obtained. For the relative rate method, rate constants for the reaction of OH with DMS were found to increase with increasing concentrations of added NO. These results are compared with the large body of kinetic and mechanistic data previously reported in the literature.     

FTIR spectra of matrix isolated complexes between sulfur compounds

The matrix isolation technique has been coupled with Fourier transform infrared spectroscopy to isolate and to characterize the complex between methanethiol and dimethyl sulfide as well as the complexes between sulfur dioxide and a series of dialkyl sulfides including (CH₃)₂S, (C₂H₅)₂S and CH₃SC₂H₅. The 1:1 CH₃SH-S(CH₃)₂ complex was isolated and characterized by the i.r. frequency shifts of the sub-molecule methanethiol. In each of the SO₂/sulfide systems, evidence was obtained for the formation of a 1:1 complex through the disulfide interaction. Vibrational assignments were also suggested for the 1:2, sulfide-(SO₂)₂, complexes.     

Activity of cobalt sulfide catalysts in the hydrogenolysis of dimethyl disulfide to methanethiol: Effects of the nature of a support and the procedure of supporting a cobalt precursor

The conversion of dimethyl disulfide to methanethiol on various catalysts containing supported cobalt sulfide in an atmosphere of hydrogen was studied at atmospheric pressure and T = 190°C. On CoS introduced into the channels of zeolite HSZM-5, the process occurred at a high rate but with a low selectivity for methanethiol because the proton centers of the support participated in a side reaction with the formation of dimethyl sulfide and hydrogen sulfide. Under the action of sulfide catalysts supported onto a carbon support, aluminum oxide, silicon dioxide, and an amorphous aluminosilicate, the decomposition of dimethyl disulfide to methanethiol occurred with 95–100% selectivity. The CoS/Al₂O₃ catalysts were found to be most efficient. The specific activity of alumina-cobalt sulfide catalysts only slightly depended on the phase composition and specific surface area of Al₂O₃. The conditions of the thermal treatment and sulfurization of catalysts and, particularly, the procedure of supporting a cobalt precursor onto the support were of key importance. Catalysts prepared through the stage of supporting nanodispersed cobalt hydroxide were much more active than the catalysts based on supported cobalt salts.     

The reaction of OH radicals with dimethyl sulfide

The kinetics of the gas phase reaction of OH radicals with dimethyl sulfide (CH₃SCH₃) have been studied at various temperatures and total pressures using two relative rate methods and a flash photolysis technique. For the relative rate methods, rate constants were measured at 296 ± 2 K as a function of the O₂ pressure at a total pressure of ca. 740 torr. Data from these three experimental techniques were not in agreement. It is concluded that the relative rate techniques are subject to secondary reactions, possibly involving CH₃S radicals. A rate constant of (2.5) × 10^?12 e^{(130 = 102)/T} cm³ molecule^?1 s^?1 obtained using the flash photolysis-resonance fluorescence data in the absence of O₂, and which is in agreement with the lower range of values previously reported in the literature, is recommended.     

Copper(I) iodide dimethyl sulfide catalyzed 1,4-addition of alkenyl groups from alkenyl-alkylzincate reagents

The presence of catalytic quantities of the copper(I) iodide dimethyl sulfide complex {(CuI)₄(SMe₂)₃} with alkenyl-alkylzincate reagents allows for the complete chemoselective 1,4-addition of various alkenyl groups to a number of α,β-unsaturated carbonyl compounds in CH₂Cl₂ at +35 °C. The 1,4-addition of the mixed vinylzincate reagent is more efficient than the corresponding vinylzirconocene reagent in CH₂Cl₂ or THF. By employing CH₂Cl₂ as a medium, the asymmetric copper-catalyzed addition of the vinyl groups to α,β-unsaturated imides is facilitated by the presence of TMSOTf to give excellent yields and up to 95:5 diastereomeric ratios (dr).     

Selective Determination of Dimethyl Sulfide in Seawater Using Reactive Extractive Electrospray Ionization Mass Spectrometry

Reactive extractive electrospray ionization mass spectrometry was used for the rapid, sensitive determination of dimethyl sulfide in seawater without sample pretreatment. Using silver cations (Ag⁺) as the ionic reagent, the analyte was selectively extracted from seawater to form adduct ions of [CH₃SCH₃?+?Ag]⁺. The characteristic product ions of Ag⁺, generated from parent ions of [CH₃SCH₃?+?Ag]⁺ by tandem mass spectrometry, were used for quantitative analysis. A linear calibration curve was obtained from 1 to 10,000 pg/mL with acceptable relative standard deviations of 3.2–8.1%. This method provided a low limit of detection (0.3 pg/mL), reasonable recovery (82–111%), and acceptable precision (3.9 and 4.2% for intraday and interday measurements). Trace dimethyl sulfide was determined in seawater by this method. These results demonstrate that reactive electrospray ionization mass spectrometry is suitable for the rapid, reliable, and sensitive determination of dimethyl sulfide in seawater. Further investigations will improve our understanding on the relationship between global climate change and dimethyl sulfide concentrations in the ocean.     

Chemical polarization of nuclei. Proton polarization during thermal decomposition reaction of dimethyl perdiglutarate

Proton chemical polarization was observed in methyl butyrate, γ-butyrolactone and in some other products of the dimethyl perdiglutarate decomposition reaction. The polarization pattern of the α-CH₂ and β-CH₂ groups in butyrolactone is just as one would expect in the products of the CH₃OCH₂CH₂?H₂ radical which has left the pair of identical radicals. Thus butyrolactone is formed from the CH₃OCH₂CH₂?H₂ radical by means of intramolecular cyclization and elimination of the methyl radical.     

Reaction of acetylferrocene with dimethylformamide dimethyl acetal and some transformations of the reaction product

1-Dimethylamino-3-ferrocenyl-3-oxoprop-1-ene was synthesized by the reaction of acetylferrocene with dimethylformamide dimethyl acetal. Its reactivity in the reactions with mononucleophilic (sodium salts of phenol, thiophenol, benzenesulfinate, diethylphosphorous acid) and binucleophilic reagents (hydrazine hydrate, hydroxylamine, amidines, 1,2-diaminobenzene, 2-aminophenol, 2-aminothiophenol) and methyl iodide was studied. As a result, we obtained new ferrocene-containing α-keto-unsaturated compounds and heterocycles of pyrazole, isoxazole, pyrimidine, and benzazepine series. In the reaction with CH₃I formed ferrocenoylacetylene which in the presence of dicarbonyl-bis(triphenylphosphine)nickel catalyst easily trimerized to give a mixture of 1,2,4- and 1,3,5-triferrocenoylbenzene.     

Synthesis and structure of dimethyl 3-(2-furoyl)pyrazole-4,5-dicarboxylate

1,3-Dipolar cycloaddition to the diazomethine grouping takes place in the reaction of 2-diazoacetylfuran with dimethyl acetylenedicarboxylate. The structure of the crystalline reaction product, viz., dimethyl 3-(2-furoyl)pyrazole-4,5-dicarboxylate, was investigated by x-ray diffraction analysis. The entire molecule, except for one of the two CO₂CH₃ groups, forms a planar conjugated system. The spectral characteristics of the synthesized compounds are presented.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 91–94, January, 1982.