Sulfur Double Bond Research Articles

Interactions of Acetylene-Derived Thioester Collectors with Gold Surfaces: A First-Principles Study

The high reactivity of the acetylene group enables the formation of strong chemical bonds with active sites on mineral surfaces, thereby improving the flotation performance of gold minerals. This study utilized density functional theory (DFT) to analyze the quantum chemical parameters of structure, Mulliken population, and the frontier orbitals of a thioester collector containing an acetylene group, PDEC (prop-2-yn-1-yl diethylcarbamodithioate). PDEC was compared with analogous thioester collectors Z-200 and Al-DECDT. The interaction mechanism of PDEC on the Au(1 1 1) surface was simulated, followed by empirical validation through adsorption experiments. The findings indicate that the S atom of PDEC in the carbon–sulfur group exhibits shorter covalent bond lengths, and has reduced carbon–sulfur double bonds and Mulliken population, resulting in enhanced electron localization. This confers greater selectivity to PDEC during its adsorption on mineral surfaces. Frontier orbital analysis shows that the electrons of the acetylene group possess a notable electron-accepting capacity, significantly influencing the frontier orbital energy of PDEC and playing a pivotal role in the bonding interaction with mineral surfaces. Both the S atom in the carbon–sulfur group and its acetylene group establish stable adsorption structures with the A(111) surface in a single coordination mode. The adsorption energy sequence is PDEC > Al-DECDT > Z-200. Partial density of states demonstrates that the S 3p orbit of the carbon–sulfur group hybridizes with the Au 5d orbit, while the C 2p orbit of the acetylene group engages in weaker back-donation bonding with the Au 5d orbit. This is corroborated by the electron density difference and post-adsorption Mulliken population analyses, revealing that the S atom of the carbon–sulfur group in PDEC donates electrons to the Au atom, forming dominant positive coordination bonds, whereas the acetylene group accepts partial electrons from the Au atom, resulting in weaker back-donation bonds. The adsorption experiments align with the DFT adsorption energy results.

Heteroatom-doped biochar devised from cellulose for CO2 adsorption: a new vision on competitive behavior and interactions of N and S

Biochar, as a potential CO2 adsorbent, is of great significance in addressing the problem of global warming. Previous studies have demonstrated that the CO2 adsorption performance of biochar can be improved by nitrogen and sulfur doping. Co-doping can integrate the structure and function of two elements. However, the physicochemical interaction of nitrogen and sulfur during doping and the CO2 adsorption process remains unclear in co-doped biochar. In this study, the heteroatom-doped biochar was prepared with different additives (urea, sodium thiosulfate, and thiourea) via hydrothermal carbonization, and the physicochemical interaction of nitrogen and sulfur in co-doped biochar was investigated extensively. The findings revealed that nitrogen and sulfur competed for limited doped active sites on the carbon skeleton during the co-doping process. Interestingly, thiourea retained the amino group on the surface of biochar to a great extent due to carbon–sulfur double bond breaking and bonding, which facilitated the formation of pore in the activation process. Significantly, co-doping had no significant improvement effect although nitrogen and sulfur doping separately enhanced the CO2 adsorption performance of biochar by 11.9% and 8.5%. The nitrogen-containing and sulfur-containing functional groups in co-doped biochar exhibited mutual inhibition in the process of CO2 adsorption. The findings of this study will have pertinent implications in the application of N/S co-doped biochar for CO2 adsorption.Graphical

ZnS quantum dots implanted polyaniline-wrapped corn straw catalysts for efficient photocatalytic nitrate reduction without external addition of hole scavengers

Photocatalytic reduction to harmless nitrogen gas is considered a promising method for the removal of nitrate from water. However, achieving high efficiency of photocatalytic nitrate reduction, especially without the assistance of a hole scavenger, remains a critical issue. Herein, PANI-CS (PC) is prepared by in-situ polymerization of aniline on the surface of biomass corn straw, and then ZnS QDS is loaded to synthesize ZnS QDs-PANI-CS (ZPC) catalysts for photocatalytic reduction of nitrate. The optimized ZPC shows highly selective and efficient photocatalytic reduction of NO3– without extra sacrificial agents, with the 0.8% ZPC delivering an excellent nitrate removal rate of 98.4% and N2 selectivity of 96.8%. Outstanding catalytic performance is attributed to the ZPC having higher electron mobility and longer electron lifetime. Additionally, ZnS QDs induce the conversion of the quinone ring of PANI to the benzene ring, thereby improving the reducibility of the catalyst. Most importantly, The carbon–sulfur double bond on the ZnS quantum dots and the bicarbonate on the surface of the straw are the sources of formic acid, which provides great help for the production of CO2•- with reduction activity. The introduction of ZnS QDs also enriches the Lewis acid sites on the ZPC surface, thereby enhancing the N2 selectivity, and simultaneity, the stability of the composite is consolidated due to the formation of N-Zn covalent bonds, laying the foundation for the commercialization of the catalyst. This work introduces the characteristics of self-produced formic acid into photocatalysts through ingenious design, which provides a new idea for the photocatalytic treatment of nitrate wastewater.

Reaction pathways, kinetics and thermochemistry of the chemically-activated and stabilized primary methyl radical of methyl ethyl sulfide, CH3CH2SCH2•, with 3O2 to CH2CH3SCH2OO•

Oxidation of Methyl ethyl sulfide (CH3SCH2CH3, methylthioethane, MES) under atmospheric and combustion conditions is initiated by reaction with hydroxyl radicals. Methyl ethyl sulfide (MES) radicals generated after losing an H atom via OH abstraction subsequently reacts with O2 to form chemically activated and stabilized peroxyl radical adducts. The kinetics of the chemically activated reaction between the CH2•SCH2CH3 radical and molecular oxygen are analyzed using quantum Rice–Ramsperger–Kassel (QRRK) theory for k(E) with master equation analysis and a modified strong-collision approach to account for further reactions and collisional deactivation. Thermodynamic properties of reactants, products and transition states are determined by the CBS-QB3 composite and M062X/6-311+G(2d, p) DFT methods. The reaction of CH2•SCH2CH3 with O2 forms an energized peroxy adduct •OOCH2SCH2CH3 with a calculated well depth of 26.4 kcal/mol at the CBS-Q//M062x/6-311+g(2d,p) levels of theory. Thermochemical properties of reactants, transition states and products obtained under CBS-QB3 level are used for calculation of the thermochemical and kinetic parameters. The temperature and pressure dependent rate coefficients for both the chemically activated reactions of the energized adduct and the thermally activated reactions of the stabilized adducts are presented. Stabilization and isomerization of the •OOCH2SCH2CH3 adduct are important under high pressure and low temperature. At temperatures between above 600–800 K reactions of the chemically activated peroxy adduct become important relative to stabilization under the atmospheric pressure. Two new pathways are observed, in addition to conventional hydrogen atom transfer reactions from the three carbons to the peroxy oxygen radical. One of these new paths is formation of a Criegee intermediate plus CH2•OO• plus CCS•. A second new path involves the peroxy oxygen radical addition to the sulfur moiety followed by carbon-sulfur bond cleavage with formation of carbon–oxygen and oxygen–sulfur double bonds: CH2O + S•(O)CC. These are potentially important new pathways other alkyl-sulfide peroxy radical systems under thermal or combustion conditions.

Tribochemical Behavior of Ashless Dialkyl Dithiophosphate Ester as an EP/AW Additive in Mineral Oil for Steel–Aluminum Contact

ABSTRACT Dialkyl dithiophosphate ester (DDPE) used as an extreme pressure/antiwear (EP/AW) additive in mineral base oil (BO) was introduced to a steel–aluminum contact in this study. The tribological performance of DDPE was explored by means of a universal tribotester under different loads and durations. The worn aluminum surface topographies were observed and photographed via laser scanning confocal microscopy (LSCM) and scanning electron microscopy (SEM). Tribochemical interactions between the additive and aluminum surface were investigated using energy-dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The distinction of chemical structure between lubricant untapped and the counterpart retrieved after a 3-h sliding process was detected by Fourier transform infrared spectroscopy (FTIR). The friction coefficient of a BO + DDPE-lubricated friction pair under 300 N shows the lowest value. LSCM and SEM images show that the aluminum surface lubricated with BO + DDPE was well protected under a high loading condition of 300 N, and the 3-h sliding process deteriorated the surface topography. However, DDPE was not able to offer an effective lubricating film under a mild condition of 50 N. EDS results of S and P elements on the worn surface indicate that a tribochemical film was generated under 300 N in the sliding process. XPS results further show that the chemical compounds in the tribochemical film included Al2S3, Al2(SO4)3, AlPO4, and Al2O3. The P-containing compound in the tribofilm acted as a sacrificial layer, whereas the S-containing compounds were more durable. FTIR analyses demonstrate that the phosphorus–sulfur double bond was broken up due to the tribochemical interactions.

ChemInform Abstract: Oxidative Desulfurization—Fluorination Reaction Promoted by [bdmim][F] for the Synthesis of Difluorinated Methyl Ethers.

Abstract A new ionic liquid [bdmim][F] has been prepared and fully characterized. Its potential as a fluoride source for the desulfurization–fluorination process has been evaluated with success. The carbon–sulfur double bond of xanthates and thiocarbonates has been difluorinated to give rise to small libraries of halogenated ketals and thioketals.

Oxidative desulfurization–fluorination reaction promoted by [bdmim][F] for the synthesis of difluorinated methyl ethers

A new ionic liquid [bdmim][F] has been prepared and fully characterized. Its potential as a fluoride source for the desulfurization–fluorination process has been evaluated with success. The carbon–sulfur double bond of xanthates and thiocarbonates has been difluorinated to give rise to small libraries of halogenated ketals and thioketals.

Isolation of a Three‐Coordinate Boron Cation with a Boron–Sulfur Double Bond

The reaction of the bulky bis(imidazolin-2-iminato) ligand precursor (1,2-(L(Mes)NH)2-C2H4)[OTs]2 (1(2+) 2[OTs](-); L(Mes) = 1,3-dimesityl imidazolin-2-ylidene, OTs = p-toluenesulfonate) with lithium borohydride yields the boronium dihydride cation (1,2-(L(Mes)N)2-C2H4)BH2[OTs] (2(+) [OTs](-)). The boronium cation 2(+) [OTs](-) reacts with elemental sulfur to give the thioxoborane salt (1,2-(L(Mes)N)2-C2H4)BS[OTs] (3(+) [OTs](-)). The hitherto unknown compounds 1(2+) 2[OTs](-), 2(+) [OTs](-), and 3(+) [OTs](-) were fully characterized by spectroscopic methods and single-crystal X-ray diffraction. Moreover, DFT calculations were carried out to elucidate the bonding situation in 2(+) and 3(+). The theoretical, as well as crystallographic studies reveal that 3(+) is the first example for a stable cationic complex of three-coordinate boron that bears a B=S double bond.

Cleavage of oxygen–sulfur double bonds and carbon–sulfur bonds: unusual highly selective electrophilic addition of allenylic sulfoxides

Selective cleavage and formation of covalent bonds is an everlasting topic in the science of synthesis. Recently, much attention has been paid to the activation and functionalization of inert covalent chemical bonds such as C–H, C–O, C–Cl bonds, etc. In this edge article, we report that hydrogen bonding may mediate efficient and highly selective cleavage of OS and C–S bonds in 1,2-allenyl sulfoxides with I2 and BnSH, which transfer the oxygen to the adjacent allenylic carbon atom forming a ketone or aldehyde carbonyl functionality with one CC bond in the allene moiety remaining in a highly stereoselective manner. This method provides a general and highly stereoselective route to the synthetically important yet difficult to prepare polysubstituted enals or enones.

ChemInform Abstract: Synthesis of Difluorodithiopyruvic Acid Derivatives.

The reaction of cadmium sulfide with 1,1-dichloro-3,3-difluoro-2-oxo-1-propylthiopropane yields difluorodithiopyruvic propionate. This reacts with morpholine to give difluorodithiopyruvic morpholide; it also undergoes a cycloaddition reaction to the carbon–sulfur double bond with dimethylbutadiene to form 2-difluoroacetyl-4,5-dimethyl-2-propylthio-3H,6H-thiopyran.

Reactions of Dimethoxycarbene with Carbon—Sulfur Double Bonds

AbstractFor Abstract see ChemInform Abstract in Full Text.

Vibration assignment of carbon–sulfur bond in 2-thione-1,3-dithiole-4,5-dithiolate derivatives

The higher frequency peak near 1050 cm −1 of the doublet in the infrared and Raman spectra of 2-thione-1,3-dithiole-4,5-dithiolate (DMIT) derivatives corresponds mainly to the stretching vibration of carbon–sulfur double bond in the terminal SCS 2 fragments of DMIT skeletons while the lower one corresponds mainly to the Fermi resonance peak between overtones of symmetric stretching vibration of two carbon–sulfur single bond in the SCS 2 fragment of DMIT skeletons and the higher frequency. On the other hand, the higher frequency near 500 cm −1 corresponds mainly to the symmetric stretching vibration of two carbon–sulfur single bond in the SCS 2 fragments of DMIT skeletons while the lower one corresponds mainly to the symmetric stretching vibration of the four carbon–sulfur single bond in the S 2CCS 2 fragments of DMIT skeletons.

Substituent effects on the stabilization of a germanium–sulfur double bond

Substituent effects on the potential energy surface of X 2GeS (X=H, F, Cl, Br, CH 3, and SiH 3) were studied by using the B3LYP and CCSD(T) methods. Our theoretical investigations indicate that the kinetic and thermodynamic stabilities of substituted germanethiones are strongly dependent on the substituent. That is to say, dihalogen substitution can dramatically stabilize X 2GeS with respect to XGe–SX. Thus, F 2GeS, Cl 2GeS and Br 2GeS should be viable candidates for experimental observation.

ChemInform Abstract: Photochemical Reactions of N-Acylbenzoxazole-2-thiones.

The photochemical reactions of N-acylbenzoxazole-2-thiones 1 are examined. Irradiation of N-acylbenzoxazole-2-thiones 1 in the presence of a variety of alkenes 2 yields 2-substituted benzoxazoles 3–20 and/or the unexpected products, iminothietanes 21–29 by intramolecular trapping of the acyl group by thiolate anion of the zwitterionic intermediate I and by the phenolate anion of the zwitterionic intermediate II, respectively, derived from the spirocyclic aminothietanes AT which are formed by regioselective [2+2] cycloaddition of the carbon–sulfur double bond of 1 to the alkene double bond.

Electrophilic Substitution of Phenols with α,α′-Dioxothiones andortho-Thioquinones

α,α′-Dioxothione 1a and ortho-thioquinones 2a and 2b are able to react with several phenols and N,N-dimethylaniline to give the corresponding alkyl aryl or diaryl sulfides. The mechanism of this reaction was proved to be an electrophilic aromatic substitution undergone by the highly polarised carbon−sulfur double bond. Following this procedure, the atropoisomeric biphenyl compound 26 was also prepared.

Photochemical reactions of N-acylbenzoxazole-2-thiones

The photochemical reactions of N-acylbenzoxazole-2-thiones 1 are examined. Irradiation of N-acylbenzoxazole-2-thiones 1 in the presence of a variety of alkenes 2 yields 2-substituted benzoxazoles 3–20 and/or the unexpected products, iminothietanes 21–29 by intramolecular trapping of the acyl group by thiolate anion of the zwitterionic intermediate I and by the phenolate anion of the zwitterionic intermediate II, respectively, derived from the spirocyclic aminothietanes AT which are formed by regioselective [2+2] cycloaddition of the carbon–sulfur double bond of 1 to the alkene double bond.

Zwitterionic 18-Electron d0-Anionic Metallocene Complexes

Formal [3+2] cycloaddition reactions between the α-phosphino zirconaindene 1 and various cumulenes [CO2, CS2, Cy−NCN−Cy (Cy = cyclohexyl), R−NCS (R = Me, Ph), R−NCO (R = Ph, tBu)] afford stable zwitterionic monomeric five-coordinated anionic bis(cyclopentadienyl) zirconium complexes 2−6. Single-crystal X-ray structures of two of these compounds (3, 6b) are reported. A related biszwitterionic zirconocene complex 9 is prepared through the reaction of carbon disulfide with the tricyclic α-phospholane zirconaindan 7; in this case cycloaddition reactions take place on the two carbon sulfur double bonds of CS2.

Synthesis and X-ray crystal structure of [Na(18-crown-6)][U(Cp*)2(SBut)(S)], the first f-element compound containing a metal–sulfur double bond

The C–S bond cleavage of a thiolate ligand of [U(Cp*)2(SBut)2] was induced by treatment with Na(Hg) and the title compound was isolated after addition of 18-crown-6; the crystal structure exhibited the unsupported U–S–Na linkage of the molecular complex, with a U–S bond distance of 2.462(2) A.

Synthesis, Structure, and Reactivity of the First Kinetically Stabilized Silanethione

Diaryltetrathiasilolanes 2a,b, bearing bulky aryl groups such as 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt), mesityl (Mes), and 2,4,6-triisopropylphenyl (Tip), were obtained by thermal reaction of dihydrosilane 3a with elemental sulfur, reaction of highly hindered disilene 4 with sulfur, or reduction of dibromosilane 6 followed by addition of sulfur. The molecular structure of 2a was determined by X-ray crystallographic analysis. Desulfurization of 2a at −78 °C afforded a silicon−sulfur double bond compound (silanethione 7a). Although the formation of 7a was confirmed by various trapping reactions, 7a dimerized at room temperature to give 1,3,2,4-dithiadisiletane 8, whose molecular structure was determined by X-ray crystallographic analysis. Desulfurization of 2b afforded the first stable silanethione, Tbt(Tip)SiS (7b), as yellow crystals, which were thermally stable under inert gas up to its melting point (185−189 °C) and showed λmax (n→π*) at 396 nm and νSiS (Raman) at 724 cm-1. The chemical shift of δSi 166.56 in the 29Si NMR spectrum is greatly downfield-shifted, characteristic of a silathiocarbonyl unit. Comparison of the electronic spectra (n→π*) of a series of R1R2MS (M = C, Si, Ge, Sn) compounds revealed an interesting trend: λmax is significantly blue-shifted on going from M = C to M = Si, whereas λmax's for R1R2MS (M = Si, Ge, Sn) are red-shifted on increasing the atomic number of M. This trend is also found in calculated values for H2MS (M = C, Si, Ge, Sn). The X-ray crystallographic analysis of 7b revealed that there are two nonidentical silanethiones in the asymmetric unit and the silathiocarbonyl units have completely trigonal-planar geometry, with silicon−sulfur double bond lengths of 1.948(4) and 1.952(4) Å, which are about 0.2 Å shorter than the typical Si−S single bond length (ca. 9% shortening), indicating an unambiguous double bond character between silicon and sulfur. Despite the presence of two very bulky substituents on silicon, 7b easily reacted with water, methanol, phenyl isothiocyanate, mesitonitrile oxide, and 2,3-dimethyl-1,3-butadiene to afford the corresponding adduct or cycloadduct. Theoretical calculations were carried out for the σ and π bond energies of H2MX (M = C, Si, Ge, Sn, Pb; X = O, S, Se, Te) and for the single and double bond lengths of H3MXH and H2MX, and the theoretical backgrounds of the chemistry of group 14−group 16 double bond species were discussed.

1-Ethyl-3-methylthio-4-thioxo-1,4-dihydroquinoline or 1-ethyl-3-(methylthio)quinolinium-4-thiolate?

The title compound 1 crystallizes in the monoclinic space group C2/c with a = 16.720(4), b = 8.577(1), c = 15.855(4) A, and β = 98.37(1)°. The thiocarbonyl group C – S bond (1.697(4) A) is longer than those of typical carbon–sulfur double bonds in thiones. Bond lengths and bond angles in the pyridine ring of the title compound are close to the values found for pyridinium salts.