Dimethyl Sulfide Molecules Research Articles

Preparation and characterization of the dimethyl sulfide-β-cyclodextrin inclusion complex.

Dimethyl sulfide has been widely used in flavors and can also be used as a solvent and catalyst. However, dimethyl sulfide is volatile, and its lasting power is weak. Furthermore, dimethyl sulfide is insoluble in water and is unstable in some cases. This study concentrated on the encapsulation of dimethyl sulfide in β-cyclodextrin to form an inclusion complex and to improve the durability, water solubility, and stability of dimethyl sulfide. The product was successfully produced and characterized by scanning electron microscopy, diffraction of X-rays, and thermal analysis. The dimethyl sulfide loading capacity is 6.40±0.08%. Based on the thermal release characteristics of dimethyl sulfide, the kinetic and thermodynamic parameters were obtained. The apparent activation energy, pre-exponential factor, and reaction order of the dimethyl sulfide release reaction were obtained and the values were 95.0±0.1kJ/mol,1.03×1015 s-1 , and 1, respectively. The activation entropy change, activation enthalpy change, and activation Gibbs free energy change were 41.6 J/K, 95.0kJ/mol, and 81.3kJ/mol, respectively, during the process of dimethyl sulfide release at 56.7℃. To make it clear that the dimethyl sulfide molecule interacts with β-cyclodextrin molecule, molecular simulation was used to investigate the formation process of the dimethyl sulfide-β-cyclodextrin inclusion complex. The binding energy and the optimized structure were obtained. When the Z coordinate of the S atom in the dimethyl sulfide molecule is 1.1×10-10 m, the binding energy attained the minimum value, -51.3kJ/mol. These basic data are helpful for understanding the dimethyl sulfide-β-cyclodextrin inclusion complex formation mechanism and the interaction between dimethyl sulfide and β-cyclodextrin. PRACTICAL APPLICATION: By forming an inclusion complex with β-cyclodextrin, the stability, durability, and water solubility of dimethyl sulfide can be improved. Dimethyl sulfide-β-cyclodextrin inclusion complex can be widely used in the food, beverage, flavor, and fragrance industries. The kinetic and thermodynamic parameters, binding energy, and the results of molecular simulation are helpful to understand the dimethyl sulfide-β-cyclodextrin inclusion complex formation mechanism and the interaction between dimethyl sulfide and β-cyclodextrin.

Carbonyl sulfide and dimethyl sulfide adsorption studies on novel square-octagon antimonene sheets – A first-principles study

Using the first-principles study, we studied the structural and electronic attributes of square-octagon antimonene nanosheet (so-SbNS). Firstly, the structural and thermal stability of so-SbNS is ascertained. The energy band gap of so-SbNS is recorded as 0.814 eV. Furthermore, the so-SbNS is deployed as base material to adsorb carbonyl sulfide (COS), and dimethyl sulfide (DMS) molecules. The physical adsorption of COS and DMS molecules is noticed on so-SbNS. The so-SbNS behaves as the acceptor of electrons observed from charge transfer and electron density difference results. The band structure and projected density of states changes are noticed due to COS and DMS adsorption on so-SbNS. The results convey that so-SbNS is new material towards the detection of COS and DMS molecules emitted from solid waste.

DFT study of the dimethyl sulfoxide reduction on silicene

We have studied the minimum energy pathway for the dimethyl sulfoxide reduction on silicene substrates. Starting with a configuration in which the molecule and the substrate are not interacting, the dimethyl sulfide molecule is physisorbed on the silicene as a first step, until it is finally reduced with the formation of silicene oxide units. As the reaction proceeds, the system gains energy, favoring the reduction of the molecule. The energy barrier for the reaction to proceed forward is 0.20 eV, which is 0.30 eV lower than the energy barrier for desorption. At the maximum coverage of ¼ monolayer, silicene oxide lines are formed. These results pave the way to use silicene as a substrate to reduce dimethyl sulfoxide (a molecule with low dose toxicity) to dimethyl sulfide, an important compound in the global ecosystem cycle. In the final state, the DMS molecule is physisorbed on silicene oxide. Therefore, this reaction is also a viable and efficient mechanism for oxidation of silicene.

The effect of the adsorbate layer on the work function reduction of gold substrates under external electric fields

The interface interaction between the dimethyl sulfide (DMS) molecule and the gold substrate under external electric fields is investigated by density functional theory method. The polarized DMS adsorbate reduces the work function of the gold substrate while the induced substrate dipole upon the adsorption slightly increases the work function. The DMS layer partially shields the Au(111) substrate from the electric fields and the vacuum level of DMS/Au(111) shifts less than of Au(111) in consequence. Under electric fields pointing outward from the Au(111) surface, both the reduction of work function and the adsorption of DMS molecule are enhanced on the surface. We also suggest the possible application of the field-effect transistor (FET) sensor with gold gate for detecting DMS molecule by utilizing the reduction of substrate work function upon adsorption. The effects of coverage and electric field on the theoretical sensitivity of the sensor are also discussed.

Effect of valence of copper on adsorption of dimethyl sulfide from liquid hydrocarbon streams on activated bentonite

AbstractSamples of activated bentonite and activated bentonite modified with CuCl and CuCl2, separately, were tested as dimethyl sulfide (DMS) adsorbents. The adsorption and desorption behaviours of DMS on the adsorbents were studied systematically. The adsorbents were characterised by nitrogen adsorption, XRD, and DMS-TPD tests. The addition of CuCl and CuCl2 to the activated carbon significantly enhanced the adsorption capacity of DMS, despite a notable decrease in the specific surface area and total pore volume of the activated bentonite. It is presumed that copper cation species may act as an adsorption site for DMS. The adsorption capacity of Cu(II)-bentonite was better than that of Cu(I)-bentonite. The DMS-TPD patterns indicate that the stronger electrophilicity of Cu(II) compared to that of Cu(I) caused it to interact with the DMS molecules more strongly, thus contributing to a better adsorptive performance. The Cu(II)-bentonite calcined at 150°C had the best DMS removal performance with a high sulphur capacity of 70.56 mg S g−1 adsorbent. The DMS removal performance became much lower with the increase in the calcination temperature, which appeared to be due to the decrease in the CuCl2·2H2O phase and the formation of the monoclinic Cu(OH)Cl phase.

Study on the adsorption behavior and mechanism of dimethyl sulfide on silver modified bentonite by in situ FTIR and temperature-programmed desorption

A high-performance adsorbent was developed by loading silver on bentonite for the adsorption of dimethyl sulfide (DMS) from liquid hydrocarbon streams under ambient conditions. It demonstrated a high saturated sulfur capacity of 80mg S/g adsorbent when the bentonite was loaded with 8wt% Ag+ and calcined at 150°C. The prepared adsorbents were characterized by adsorption of nitrogen (BET), Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), pyridine Fourier transform infrared spectroscopy (pyridine-FTIR) and Thermogravimetric Analysis (TG). The results showed that the silver species dispersed on the surface of bentonite had an important role in determining the DMS removal performance while the surface acid sites of adsorbent had little correlation with the DMS removal performance. Combined techniques of temperature programmed desorption of DMS (DMS-TPD) and in situ Fourier transform infrared spectroscopy (in situ FTIR) were used to investigate the adsorption mechanism of DMS on raw bentonite and Ag+ modified bentonite, respectively. The results revealed that three interaction patterns were existed between the adsorbed DMS and raw bentonite while two interaction patterns were observed between adsorbed DMS and Ag+ modified bentonite. The DMS molecules hardly entered into the interlayer of Ag+ modified bentonite due to the strong interactions between DMS molecules and silver cations.

Vanadium (IV) benzenedicarboxylate: A novel adsorbent for selective separations

The crystal structure of VOBDC (BDC = 1,4-benzenedicarboxylate) has a 1-dimensional channel system with apertures of ∼8 Å, and shows remarkable flexibility upon adsorption/desorption of various guest molecules in the channels. VOBDC can selectively and rapidly adsorb organic molecules containing sulfur on exposure to a 5% CH4/He stream with different contents of thiophene or dimethyl sulfide at ambient temperature. Selective uptake of thiophene from liquid octane with thiophene concentrations from 2000 ppmw down to 100 ppmw is also observed. X-ray crystallographic data show that the adsorbed thiophene molecules adopt a herringbone packing arrangement within the channels of VOBDC while adsorbed dimethyl sulfide molecules are disordered among several positions in the channels with the sulfur atoms pointing toward the channel walls. The observed adsorptive capacities for thiophene and dimethyl sulfide are 155 mg and 208 mg sulfur per gram of VOBDC, respectively, consistent with the crystal structure data.

The structure of monomeric unsolvated and weakly solvated (Me2Cu)Li and (Me2Cu)Cu

Density functional theory was used to study the structure of various isomers of (Me2Cu)Li (1), (Me2Cu)Cu (2), (Me2Cu)Li · 2Me2O (3), and (Me2Cu)Cu · 2Me2S (4) in the gas phase. Isomers of 1 and 3 were shown to be typical cuprates, whereas isomers of 2 and 4 should rather be treated as unsolvated and solvated methylcopper dimers, respectively. The reasons for the difference between structures 2, 4 and 1, 3 were considered. The energies of solvation of 1 by two dimethyl ether molecules (∼34 kcal/mol) and of 2 by two dimethyl sulfide molecules (∼36 kcal/mol) and the dissociation energies of all the compounds to the dimethylcuprate anion and the corresponding cation were calculated. The energies of solvation of 1 and 2 being almost equal, the transformation of 2 into 4 decreased the dissociation energy much more substantially than the transformation of 1 into 3.

Adsorption/desorption of dimethylsulfide on activated carbon modified with iron chloride

The adsorption capacity of activated carbon for the natural gas contaminant dimethylsulfide (DMS) was improved by impregnating it with FeCl3 introduced in solution to affect surface modification. A DMS adsorption mechanism and roles of impregnated FeCl3 on the capacity enhancement were proposed based on experimental tests results.Samples of activated carbon and activated carbon impregnated with FeCl3 were tested as DMS sorbents. Samples loaded with DMS were subsequently extracted with n-octane and the resulting solvents were analyzed for sulfur species using a gas chromatograph equipped with a sulfur chemiluminescence detector. No other sulfur compounds were detected in the liquid samples other than DMS. DMS, dimethyl disulfide, and carbonyl sulfide were recovered from identical DMS-adsorbed samples of activated carbon impregnated with FeCl3 subjected to temperature programmed desorption (TPD) in a nitrogen gas stream. Only DMS was recovered from the activated carbon samples. The TPD patterns indicate different kinetics of DMS desorption related to the carbon phase and the new active sites created by the FeCl3 impregnation. The new active sites improved DMS adsorption capacity and likely had stronger affinity with DMS molecule. As a reference, similar tests were investigated using methyl mercaptan (MM) as an adsorbate on the carbon sorbents. A different adsorption mechanism was found and discussed from these experimental results. Regeneration of the used carbon sorbents by thermal desorption was also explored.

Adsorption of dimethyl sulfide vapors by activated carbons

Adsorption isotherms of dimethyl sulfide vapors have been studied on two samples of granulated and two samples of fibrous activated carbons having different surface areas and associated with varying amounts of carbon–oxygen surface groups. The adsorption isotherms follow the Langmuir isotherm equation. The adsorption generally increases with increase in surface area and is strongly influenced by the presence of carbon–oxygen groups on the carbon surface. The adsorption increases on oxidation of the carbon surface which enhances the amounts of these surface groups and decreases gradually when these surface groups are eliminated on heat treatment in vacuum at 400°, 650° and 950°C. The adsorption of dimethyl sulfide obeys first order kinetics. The isosteric enthalpy of adsorption decreases with increase in surface coverage tending to be almost constant at higher surface coverages. The adsorption results suggest that the adsorption of dimethyl sulfide by activated carbons involves specific interactions between the surface acidic groups and the dimethyl sulfide molecules through chemical or quasichemical forces involving hydrogen bonding.

Dimethyl Sulfide on Cu{111}: Molecular Self-Assembly and Submolecular Resolution Imaging

The literature contains many studies of thiol-based, self-assembled monolayers (RSH); however, thioethers (RSR) have barely begun to be explored, despite having the potential advantages of being more resistant to oxidation and allowing for the control of self-assembly parallel to the surface. This paper describes a low-temperature scanning tunneling microscopy investigation of dimethyl sulfide on Cu{111}. Previous work on the adsorption of dibutyl sulfide on Cu{111} revealed that intermolecular van der Waals interactions directed the parallel ordering of dibutyl sulfide molecules in linear rows. Upon annealing to 120 K, small dibutyl sulfide domains reordered into very large, ordered domains free of defects. The current study reveals the effect of the shorter alkyl chain length of dimethyl sulfide on both the rate of diffusion and the packing structure of the molecule. At a medium surface coverage and at 78 K, it was found that dimethyl sulfide is mobile and forms large, ordered islands without the 120 K annealing that was required for dibutyl sulfide to arrange. Also, the molecular packing structure evolves from quadrupole-quadrupole interactions and results in a perpendicular arrangement of neighboring molecules instead of the parallel arrangement observed for dibutyl sulfide. We show high-resolution images of the dimethyl sulfide islands in which submolecular features are revealed. These high-resolution data allow us to propose a structural model for the adsorption site of each dimethyl sulfide molecule within the ordered structures. These results demonstrate that the length of the alkyl side chain is an important factor in determining how thioethers self-assemble on metal surfaces.

Density Functional Investigation of Methanethiol and Dimethyl Sulfide Adsorption on Zeolite

The density functional theory and cluster model methods have been employed to investigate the interactions between methanethiol, dimethyl sulfide and zeolites. The molecular complexes formed by adsorption of methanethiol or dimethyl sulfide on silanol H 3SiOSi(OH) 2OSiH 3 with five coordination forms or four coordination forms, and complexes formed by interactions of Brönsted acid sites of bridging hydroxyl H 3Si(OH)Al(OH) 2OSiH 3 with methanethiol or dimethyl sulfide have been investigated. Full optimization and frequency analysis of all cluster models have been carried out using the B3LYP hybrid method at 6–31+G (d,p) basis set level for hydrogen, silicon, aluminum, oxygen, carbon, and sulfur atoms. The structures and energy changes of different coordination forms between methanethiol and H 3Si(OH)Al(OH) 2OSiH 3, dimethyl sulfide and H 3Si(OH)Al(OH) 2OSiH 3, methanethiol and H 3SiOSi(OH) 2OSiH 3, dimethyl sulfide and H 3SiOSi(OH) 2OSiH 3 complexes have been comparatively studied. The calculated results showed the nature of interactions that led to the formation of all complexes was van der Waals force confirmed by an insignificant change of geometric structures and properties. The conclusions that methanethiol and dimethyl sulfide molecules were adsorbed on bridging hydroxyl group prior to silanol group were obtained on the basis of adsorption heat, the most stable adsorption models of a 6 ring structure for interaction between bridging hydroxyl and methanethiol, and a 7 ring structure for interaction between bridging hydroxyl and dimethyl sulfide.

Adsorption behavior of dimethylsulfide (CH 3SCH 3) on Ni(1 1 0) surface studied by NEXAFS and XPS

Orientation and charge transfer upon adsorption of dimethylsulfide (CH 3SCH 3) on Ni(1 1 0) surface has been studied by near-edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy (XPS) techniques. It is found that dimethylsulfide adsorbs molecularly on Ni(1 1 0) surface. Polarization dependence S K-edge NEXAFS indicates that the S–C bond is tilted 19 ± 8° from the surface. Above room temperature, the S–C bond breaks and creates atomic sulfur. An amount of charge transfer (0.62 electron) from nickel to dimethylsulfide molecule has measured using S 1s XPS.

Hexacoordination of a dimethyl sulfide molecule.

Interaction of the trifunctional Lewis acid [(o-C6F4Hg)3] (1) with dimethyl sulfide in dichloroethane leads to the formation of an extended supramolecule which features sandwiched dimethyl sulfide molecules. The sulfur atom of the latter interacts simultaneously with the mercury centers of two neighboring molecules of 1 and thereby achieves hexacoordination.

Iron-57 NMR Chemical Shifts and Mössbauer Quadrupole Splittings in Metalloporphyrins, Ferrocytochrome c, and Myoglobins: A Density Functional Theory Investigation

We have evaluated the 57Fe nuclear magnetic resonance chemical shielding and Mössbauer electric field gradient tensors and their orientations for a cytochrome c model compound as well as for isopropyl isocyanide and carbon monoxy−myoglobin model systems and two simple metalloporphyrins containing bis(pyridine) and bis(trimethylphosphine) ligands, using Kohn−Sham density functional theory. For cytochrome c we used a model Fe(II) porphyrin structure together with a 1-methylimidazole base (to represent His-18) and a dimethyl sulfide molecule (to represent Met-80 in the structure of horse heart ferrocytochrome c), both located at the X-ray coordinates for cyt c Fe(II). For the Mb calculations, we used the coordinates of two recently characterized metalloporphyrins: (i-PrNC)(1-methylimidazole)(5,10,15,20-tetraphenylporphinato)Fe(II) and (CO)(1-methylimidazole)(5,10,15,20-tetraphenylporphinato)Fe(II), while literature structures were used for the bis-ligand adducts. We used a “locally dense” basis to evaluate the 57Fe shieldings and electric field gradients at iron and compared them with the measured chemical shifts and Mössbauer quadrupole splittings, respectively. There is moderately good agreement between theory and experiment for the cytochrome c and Mb 57Fe chemical shifts and shielding tensors, and very good (0.10 mm s-1 rmsd) agreement for the 57Fe Mössbauer quadrupole splittings, using the following basis sets and functional: a Wachters' all electron representation for iron, a 6-311++G(2d) basis for all atoms directly attached to iron, 6-31G* for the second shell and 3-21G* bases for the other more distant atoms, together with a B3LYP hybrid exchange-correlation functional. Extensive tests with other functionals and basis set schemes are also reported. The shift and electric field gradient tensor orientations are generally close to obvious molecular symmetry axes, with the skew of the shielding tensor reversing sign on transition from strong to weak ligand fields. The paramagnetic contribution to shielding overwhelmingly dominates overall shielding and the variations seen between weak ligand field (bis(pyridine), cytochrome c) and strong ligand field (CO, PMe3, i-PrNC) systems. Poor accord between theory and experiment is obtained for the 57Fe chemical shifts when MbCO models having highly distorted X-ray geometries are employed, suggesting that the Fe−C−O is close to the porphyrin normal, both in solution and in the solid state.

Ice-forming nuclei in air masses over the Gulf of Mexico

Aerosol particles collected over the Gulf of Mexico during the period from 20 July to 30 August 1986 were examined for their ability to nucleate ice by condensation-followed-by-freezing. Ice-forming nuclei (IFN) in the 0.1–0.4 μm-diameter size range nucleated ice at a temperature of −4°C; their concentrations were between 2 and 10 m −3. Fractions of aerosol particles in that size range nucleating ice at the initial (the highest) temperatures were between 10 −8 and 10 −7. Peaks in the concentration of dimethyl sulfide (DMS) (0800 h) preceded peaks in ice-nucleating temperatures (1300 h) by 5 h; this is sufficient time for DMS molecules to be oxidized to sulfates and to produce mixed aerosol particles through coagulation of different-sized aerosol particles and absorption of sulfur-bearing gas molecules. Fractions of aerosol particles larger than 0.2 μm in diameter containing SO 2− 4 ions were larger than 0.90; most of the time they were 0.99–1.00. All IFN displayed characteristic features of mixed IFN, that is of marine origin (part of IFN concentration independent of temperature) and of continental origin (part of IFN concentration dependent on temperature).