Analysis of a Complex Gaseous Mixture by TG-MS and TG-FTIR

The thermal decomposition of sodium ethyl xanthate (SEX) was used to compare the techniques of pyrolysis-gas chromatography-mass spectrometry (py-GC-MS), thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR), and TG-MS. In the py-GC-MS analysis, SEX was pyrolysed at 400°C in an inert atmosphere. Major gases evolved were carbon disulfide, diethyl sulfide, ethanol, and carbonyl sulfide. The TG of SEX exhibited a sharp mass loss at 201°C (42.3%) and a gradual mass loss at 217-325°C (20.8 %). The MS spectra of the evolved gases were complex due to overlapping of molecular, isotope, and fragment ion signals. Using the MS in selected ion monitoring mode, the major gases evolved were found to be carbon disulfide and carbonyl sulfide. The FTIR spectra of the evolved gases displayed vibrational frequencies due to alkanes, carbonyls, carbonyl sulfide, and carbon disulfide. From the analyses it was concluded that py-GC-MS provided unambiguous gas identification. Interpretation of the MS results was reliant on the py-GC-MS results, and the FTIR data was limited to identifying gases with very characteristic vibration frequencies. This revised version was published online in July 2006 with corrections to the Cover Date.     

Selective Hydrogenation of Diethyl Disulfide to Ethanethiol in the Presence of Sulfide Catalysts

The gas-phase reaction of diethyl disulfide hydrogenation at atmospheric pressure in the presence of supported transition metal sulfides was studied. The reaction of diethyl disulfide with hydrogen at T = 200°C resulted in ethanethiol, and the selectivity to ethanethiol was no lower than 94%. The selectivity decreased at a higher temperature because of diethyl disulfide decomposition to ethylene and hydrogen sulfide. The reaction of diethyl disulfide in the presence of hydrogen occurred at a higher rate and selectivity than that in an atmosphere of helium. The activity of metal sulfides supported on aluminum oxide was higher than on the other studied supports—aluminosilicate, silica gel, and a carbon support. Metal sulfides supported on Al₂O₃ were arranged in the following order according to their activity: Rh > Ru > Mo Pd > Ni > W. Bimetallic catalysts were less active than monometallic catalysts. The activity of catalysts increased with the sulfide sulfur content; the partial reduction of metal sulfides also increased the catalytic activity.     

Solid-phase microextraction—Gas chromatography to determine volatile organic sulfur compounds in the air at sewage treatment plants

Solid-phase microextraction (SPME) was applied to the determination of 7 volatile organic sulfur compounds (VOSCs), which were analysed by gas chromatography-mass spectrometry. The compounds studied were ethyl mercaptan (CH₃CH₂SH), dimethyl sulfide ((CH₃)₂S), carbon disulfide (CS₂), propyl mercaptan (C₃H₈S), butyl mercaptan (C₄H₁₀S), dimethyl disulfide ((CH₃)₂S₂) and 1-pentanethiol (C₅H₁₂S). Temperature and time conditions of SPME extraction were optimised and the method was validated, with good linearity in a calibration range between 0.1 and 1000 μg m⁻³. Method detection limits ranged between 0.01 and 0.08 μg m⁻³ and method quantification limits were between 0.10 and 0.25 μg m⁻³, allowing real samples taken from several different areas of a sewage treatment plant to be analysed. Repeatability of the method between samples went from 5.6% for pentanethiol up to 14.2% for carbon disulfide, and concentrations of total target compounds were found between 18 and 529 μg m⁻³, depending on the sampling site.     

Decomposition of Gaseous Sulfide Compounds in Air by Pulsed Corona Discharge

The effectiveness of applying a pulsed corona discharge to the destruction of olfactory pollution in air was investigated. This paper presents a comparative study of the decomposition of three representative sulfide compounds in diluted concentrations: hydrogen sulfide (H₂S), dimethyl sulfide (DMS), and ethanethiol (C₂H₅SH), which could be completely removed when a sufficient but reasonable energy density was deposited in the gas. DMS showed the lowest energy cost (around 30 eV/molecules); C₂H₅SH and H₂S had an EC of respectively 45 eV and 115 eV. The efficiency of the non-thermal plasma process increased with decreasing the initial concentration of sulfide compounds, while the energy yield remained almost unchanged. SO₂ was the only identified byproduct of H₂S decomposition, but the sulfur balance suggests the formation of undetected SO₃. The byproducts analyzed during the degradation of DMS and C₂H₅SH enabled to propose a reaction mechanism, starting with radical attack and breaking of C–S bonds.     

Copolymerization of ethylene sulfide and carbon disulfide

Ethylene sulfide was found to copolymerize with carbon disulfide to give poly(ethylene trithiocarbonate) in the presence of Hg(SC₄H₉)₂, Zn(C₂H₅)₂, or Cd(C₂H₅)₂, which are well known as the effective catalysts for the coordinated anionic copolymerization of episulfides. The structure and the composition of the copolymer was determined by the infrared and NMR spectra. To establishe the mechanism of the copolymerization, the reaction of carbon disulfide and Hg(SC₄H₉)₂, and also the ring-opening polymerization of ethylene trithiocarbonate were examined. Carbon disulfide was found to insert easily into the metal-sulfur bond of Hg(SC₄H₉)₂ under the experimental conditions of the copolymerization. On the other hand, the ring-opening polymerization of ethylene trithiocarbonate did not take place with these catalysts, occurring only with the use of sulfuric acid. From these results, the mechanism of the copolymerization was discussed.     

Four related diethyl [(arylamino)(4‐ethynylphenyl)methyl]phosphonates

Crystal structures are reported for four related diethyl [(arylamino)(4‐ethynylphenyl)lmethyl]phosphonate derivatives, namely diethyl [(4‐bromoanilino)(4‐ethynylphenyl)methyl]phosphonate, C₁₉H₂₁BrNO₃P, (I), diethyl ((4‐chloro‐2‐methylanilino){4‐[2‐(trimethylsilyl)ethynyl]phenyl}methyl)phosphonate, C₂₃H₃₁ClNO₃PSi, (II), diethyl ((4‐fluoroanilino){4‐[2‐(trimethylsilyl)ethynyl]phenyl}methyl)phosphonate, C₂₂H₂₉FNO₃PSi, (III), and diethyl [(4‐ethynylphenyl)(naphthalen‐2‐ylamino)methyl]phosphonate, C₂₃H₂₄NO₃P, (IV). The conformation of the anilinobenzyl group is very similar in all four compounds. The P—C bond has an approximately staggered conformation, with the aniline and ethynylphenyl groups in gauche positions with respect to the P=O double bond. The two six‐membered rings are almost perpendicular. The sums of the valence angles about the N atoms vary from 344 (2) to 351 (2)°. In the crystal structures, molecules of (I), (III) and (IV) are arranged as centrosymmetric or pseudocentrosymmetric dimers connected by two N—H...O=P hydrogen bonds. The molecules of (II) are arranged as centrosymmetric dimers connected by C_methyl—H...O=P hydrogen bonds. The N—H bond of (II) is not involved in hydrogen bonding.     

Heat of formation for the SH radical by photoionization mass spectrometry

Photoionization mass spectrometry has been used to measure the appearance energies for [C₂H₅]⁺ from ethanethiol, [C₃H₇]⁺ from 2-propanethiol and [C₃H₅]⁺ from 2-methylthiirane. From the known thermochemistry of these cations and their precursor molecules, a 298 K heat of formation of 138.6±0.4 kJ mol^?1 for the SH radical has been derived.     

Structure of heteroassociates formed in the HF-(C<Subscript>2</Subscript>H<Subscript>5</Subscript>)<Subscript>2</Subscript>O liquid system

The aim of this work was to determine the structure of stable heteroassociates (HAs) with the stoichiometric ratios 1:2, 2:1, and 4:1 of molecules formed in the HF-(C₂H₅)₂O binary liquid system. The stretching frequencies of HF molecules found for each HA using a special procedure for processing IR spectra were compared with the calculated frequencies V HF of the stable molecular complexes (HF)_m ((C₂H₅)₂O)_n (m = 1, 2, 4, 8; n = 1, 2) with different topologies by the density functional method (B3LYP/6-31++G(d,p)). As a result, it was shown that the most stable (among H-bonded complexes with the same stoichiometric ratio of molecules) HAs HF((C₂H₅)₂O)₂, (HF)₄ ((C₂H₅)₂O)₂, and (HF)₈-((C₂H₅)₂O)₂ formed in HF solutions in diethyl ether. All of them had a cyclic structure and a common peculiarity of structure: only one lone electron pair of the oxygen atom of the (C₂H₅)₂O molecules is involved in hydrogen bonding.     

Solubility of non polar gases in formaldehyde diethyl acetal between-10 and 30°C,and 1 Atm partial pressure of gas

Solubility measurements of the gases He, Ne, Ar, Kr, Xe, H₂, D₂, N₂, CH₄, C₂H₄, C₂H₆, CF₄, SF₆, and CO₂ in formaldehyde diethyl acetal in the range of –10 to 30°C, and a gas partial pressure of 1 atmosphere (101.32 kPa) are reported. Standard changes of thermodynamic functions for the solution process are evaluated. The scaled particle theory is used to obtain the effective Lennard-Jones 6, 12 pair potential parameters for formaldehyde diethyl acetal. Experimental solubilities values are compared with those obtained from the application of the scaled particle theory to gas liquid solubility.     

Synthesis and properties of novel ortho-metalated cobalt(I) and iron(II) complexes through Csp2-H bond activation of dibenzylphenylphosphine

Dibenzylphenylphosphine in the reaction with CoMe(PMe₃)₄ afforded complex [(Me₃P)₃Co((ortho-C₆H₄)∩P(C₆H₅)(CH₂C₆H₅))] (1) by C_sp2-H activation via ortho-metalation with P atom as anchoring group. An unexpected dinitrogen iron(II) complex [(Me₃P)₂(N₂)Fe((ortho-C₆H₄)₂∩P(C₆H₅))] (2) stabilized by two five-membered chelate rings as [CPC]-pincer ligand was formed through the reaction of dibenzylphenylphosphine with FeMe₂(PMe₃)₄ via double C_sp2-H activation. The reactions of complexes 1 and 2 with carbon monoxide delivered carbonyl complexes [(Me₃P)(CO)₂Co((ortho-C₆H₄)∩P(C₆H₅)(CH₂C₆H₅))] (3) and [(Me₃P)₂(CO)Fe((ortho-C₆H₄)₂∩P(C₆H₅))] (4). An iodo methyl cobalt(III) complex [(Me₃P)₂(Me)(I)Co((ortho-C₆H₄)∩P(C₆H₅)(CH₂C₆H₅))] (5) was isolated through the reaction of 1 with iodomethane. The structures of 1, 2, 3, 4 and 5 were determined by X-ray diffraction.     

Hydrolysis of esters of certain substitutes of 1,3,5-triazine

The mechanism of hydrolysis of esters of triazine substitutes was studied. It was shown that hydrolysis of l-menthyl esters in both alkaline and acid media at 80–120° C takes place with cleavage of the bond between the oxygen and carbon of triazine. The bond between the oxygen and carbon of alcohol is broken at 180–200° C in acid medium. The kinetics of alkaline hydrolysis of triazine esters was studied, and it was established that the stability of the latter increases in relation to the influence of the substitute in triazine in the order: C₆H₅ < NHC₆H₅ < NHC₂H₅ < N(C₂H₅)₂. A number of new C-substitutes of triazine was synthesized.We thank Prof. A. I. Korolev for the proposal, and the attention he gave to this work.     

The mechanisms of decomposition of the 1- and 2-phenyltetralin radical cations

Mechanisms for decomposition of 1- and 2-phenyltetralins were investigated using low resolution mass spectrometry and metastable ion techniques. Four primary decompositions were observed for 1-phenyltetralin radical cations: (1) the loss of C₆H₆ via a 1,4-elimination; (2) the elimination of ethene via competing losses from carbons 3 + 4 and carbons 2 + 3; (3) the loss of C₈H₈, probably through a stepwise Diels-Alder cycloreversion to expel styrene; and (4) the loss of methyl radical involving carbon 2 and possibly carbon 4. Three major decompositions were observed for 2-phenyltetralin radical cations: (1) the loss of C₈H₈, possibly through a Diels-Alder cycloreversion to expel styrene; (2) the loss of C₆H₆ via a 1,3 elimination; and (3) the loss of methyl radical from carbon 1. Various exchange reactions occur prior to these losses, but they proved to be incomplete even for metastable ions.     

Mass spectra of organometallic compounds—VIII. Some transition metal organometallic halide derivatives

The positive ion mass spectra of the transition metal organometallic halide derivatives C₅H₅M(CO)₃Cl(M ? Mo or W), C₇H₇W(CO)₂I, C₃H₅Fe(CO)₃I, [C₃H₅PdCl]₂, and [C₅H₅Mo(NO)I₂]₂ have been investigated. Further examples of the elimination of CO and C₂H₂ fragments were noted. In addition the following effects of particular interest were observed: (i) Evidence in the mass spectra of the chlorides for reactions with adventitious iodine and even bromine present in the mass spectrometer; (ii) Evidence for conversion of the compounds C₅H₅Mo(CO)₃X to the new halides [C₅H₅Mo(CO)X]₂ upon pyrolysis; (iii) Evidence for facile losses of the π-allyl group, the iodine atom, and methyl iodide in the mass spectrum of the π-allyl derivative C₃H₅Fe(CO)₃I; (iv) Evidence for loss of iodine upon introducing [C₅H₅Mo(NO)I₂]₂ into the mass spectrometer to give ions derived from [C₅H₅Mo(NO)I]₂.     

Mass spectra of organometallic compounds–XI: Pyrrolyl,indenyl and fluorenyl derivatives of manganese carbonyl

The positive ion mass spectra of the π-pyrrolyl derivatives C₄H₄NMn(CO)₂L (L = (C₆H₅)₃E or CO; E = P, As, or Sb), the π-indenyl derivatives C₉H₇Mn(CO)₂L (L = (C₆H₅)₃E or CO; E = P, As, or Sb) and the π-fluorenyl derivatives C₁₃H₉Mn(CO)₂L (L = (C₆H₅)₃P or CO) have been investigated. The relative tendencies of ions of the type [QMnE(C₆H₅)₃]⁺ (Q = π-pyrrolyl, π-indenyl, or π-fluorenyl; E = P, As, or Sb) to fragment by losses of the Q ring system and the (C₆H₅)₃E ligand are compared. Phenyl transfers from phosphorus, arsenic, or antimony to manganese to form relatively high abundances of [C₆H₅Mn]⁺ are also observed. Other processes typical of metal carbonyl derivatives (CO losses), aromatic derivatives (C₂H₂ eliminations) and (C₆H₅)₃E derivatives (phenyl losses, conversion of [(C₆H₅)₃E]⁺ directly to [C₆H₅E]⁺, and formation of [C₁₂H₈E]⁺ 9-heterofluorenyl ions) are observed in these mass spectra and are supported in many cases by the presence of appropriate metastable ions.     

Über Chalkogenolate. 140. Untersuchungen über Dialkylester von Chalkogenokohlensäuren. 3. S,Se-Dialkyldithiomonoselenocarbonate Existenzbeweis von Alkylselenoxanthaten [S2C?SeR]−

On Chalcogenolates. 140. Studies on Dialkyl Esters of Chalcogenocarbonic Acids. 3. S,Se-Dialkyl Dithiomonoselenocarbonates. Evidence for the Existence of Alkyl Selenoxanthates [S₂C? SeR]^? The esters RSe? CS? SR′ with R = R′ = C₂H₅, ⁿC₃H₇ as well as with R = ⁿC₃H₇ and R′ = C₂H₅ have been produced by three different methods. The compounds have been characterized by means of electron absorption, infrared, nuclear magnetic resonance (¹H, ¹³C, and ⁷⁷Se), and mass spectra. The unstable alkyl selenoxanthates M[S₂C? SeR], where M = Na, K and R = C₂H₅, ⁿC₃H₇, are formed by reaction of carbon disulfide with the corresponding alkane selenolate. Freshly prepared they react with alkyl iodides R′I to yield RSe? CS? SR′.     

ToF‐SIMS and computation analysis: Fragmentation mechanisms of polystyrene,polystyrene‐d5, and polypentafluorostyrene

We studied the time‐of‐flight secondary ion mass spectrometry fragmentation mechanisms of polystyrenes—phenyl‐fluorinated polystyrene (5FPS), phenyl‐deuterated polystyrene (5DPS), and hydrogenated polystyrene (PS). From the positive ion spectra of 5FPS, we identified some characteristic molecular ion structures with isomeric geometries such as benzylic, benzocyclobutene, benzocyclopentene, cyclopentane, and tropylium systems. These structures were evaluated by the B3LYP‐D/jun‐cc‐pVDZ computation method. The intensities of the C₇H₂F₅⁺ (m/z = 181), CyPent‐C₉H₃F₄⁺ (m/z = 187), CyPent‐C₉H₄F₅⁺ (m/z = 207), and CyPent‐C₉H₂F₅⁺ (m/z = 205) ions were enhanced by resonance stabilization. The positive fluorinated ions from 5FPS tended to rearrange and produce fewer fluorine‐containing molecular ions through the loss of F (m/z = 19), CF (m/z = 31), and CF₂ (m/z = 50) ion fragments. Consequently, the fluorine‐containing polycyclic aromatic ions had much lower intensities than their hydrocarbon counterparts. We propose the fragmentation mechanisms for the formation of C₅H₅⁺, C₆H₅⁺, and C₇H₇⁺ ion fragments, substantiated with detailed analyses of the negative ion spectra. These ions were created through elimination of a pentafluoro‐phenyl anion (C₆F₅⁻) and H⁺, followed by a 1‐electron‐transfer process and then cyclization of the newly generated polyene with carbon‐carbon bond formation. The pendant groups with elements of different electronegativities exerted strong influences on the intensities and fragmentation processes of their corresponding ions.     

Three-dimensional representation of metastable peaks at high mass resolution

Isobaric daughter ions formed from a common metastable ion have been analysed at high mass resolution. A three-dimensional representation is used to summarize the data for competitive CO and C₂H₄ losses and competitive CHO˙ and C₂H₅˙ losses from metastable molecular ions of cyclohexanone.     

Acetylene hydrochlorination over tin nitrogen based catalysts: effect of nitrogen carbon-dots as nitrogen precursor

The catalysts comprising the main active compounds of Sn-Nx were synthesized using trichlorophenylstannane ((C₆H₅)Cl₃Sn), nitrogen carbon-dots (NCDs), and activated carbon (AC) as starting materials, and the activity and stability of catalysts was evaluated in the acetylene hydrochlorination. According to the results on the physical and chemical properties of catalysts (TEM, XRD, BET, XPS and TG), it is concluded that NCDs@AC can increase (C₆H₅)Cl₃Sn dispersity, retard the coke deposition of (C₆H₅)Cl₃Sn/AC and lessen the loss of (C₆H₅)Cl₃Sn, thereby further promoting the stability of (C₆H₅)Cl₃Sn/AC. Based on the characterization results of C₂H₂-TPD and HCl adsorption experiments, we proposed that the existence of Sn-N_x can effectively strengthen the reactants adsorption of catalysts. By combing the FT-IR, C₂H₂-TPD and Rideal-Eley mechanism, the catalytic mechanism, in which C₂H₂ is firstly adsorbed on (C₆H₅)Cl₃Sn to form (C₆H₅)Cl₃Sn-C₂H₂ and then reacted with HCl to produce vinyl chloride, is proposed.     

Some observations on the thermal behaviour of curcumin under air and argon atmospheres

The TG, DTG and DTA curves of curcumin(I) have been recorded in static air and inert dynamic argon atmosphere over the range between ambient temperature and 600°–700°C using a Netzsch thermal analyser STA 429. Careful examination of these curves reveals appreciable differences in the behaviour of I under either atmospheres, which are easily recognized by comparing the profiles of their thermal curves, particularly in the melting point, thermalL stability of intermediates, percent weight loss and exothermicity of the chemical processes. Gaschromatographic analysis of volatile pyrolysates trapped during thermal analysis indicates the formation of (CH₃)₂CO, CH₃COH and C₆H₅OCH₂COOH (phenyl oxyacetic acid). However, in static air CO₂ and H₂O were identified as well. X-ray diffractometry reveals the formation of amorphous carbon as a final product in argon and a mixture of amorphous carbon and graphite in air. It seems that the relatively high mass of argon plays an important role in the reactions and stability of intermediates. In either atmospheres curcumin is thermally stable up to 249°C withm.p. of 176.4°–177.5°C. The unique shape of the DTA curve of I could be used forits identification.