Reversible Uptake of COS,CS2, and SO2: Ionic Liquids with O‐Alkylxanthate,O‐Alkylthiocarbonyl,and O‐Alkylsulfite Anions

CO₂‐binding organic liquids (CO₂BOLs) are mixtures of a base (typically an amidine or guanidine) and an alcohol, and have been shown to reversibly capture and release CO₂ with low reaction energies and high gravimetric CO₂ capacity. We now report the ability of such liquid blends to chemically bind and release other acid gases such as CS₂, COS, and SO₂ analogously to CO₂. These systems bind with sulfur‐containing acid gases to form colored ionic liquids with new O‐alkylxanthate, O‐alkylthiocarbonyl, and O‐alkylsulfite anions. The capture and thermal stripping of each acid gas from these systems and their applicability towards flue gas desulfurization is discussed.     

Quantification of several atmospheric gases from high resolution infrared solar spectra obtained at the south pole in 1980 and 1986

Simultaneous total column amounts of a number of minor and trace atmospheric gases above the South Pole in December 1980 and December 1986 have been deduced from analysis of high resolution solar absorption spectra recorded (by F. J. M. and F. H. M.) from Amundsen-Scott South Pole Station. These spectra also contain some limited information on the vertical profiles of the observed atmospheric gases.The data sets were recorded with a Bomem Michelson-type interferometer and analyzed with a spectral least-squares fitting procedure, utilizing the best available spectroscopic line parameters and absorption cross sections. Because the same instrument, line parameters, and analysis method have been used in analyzing the December 1980 and December 1986 data sets, the precision in comparing the column amounts from these two dates is rather high, about 10–20% for the stronger absorbing gases. For this reason, it has been possible to quantify or determine upper limits for differences between the December 1980 and December 1986 total column amounts, of a number of atmospheric gases including O₃, N₂O, HNO₃, CO₂, CH₄, and CF₂C_{1 2} (CFC 12). In addition, vertical column amounts for a number of atmospheric gases covered only in the December 1986 observations have been derived, including HC1, NO, NO₂, and C₂H₆. Some of these results will be discussed here. The HC1 measurements are especially interesting since the observed amounts are higher than expected from observations made at lower latitudes in the northern and southern hemispheres.     

Mechanism of thermal decomposition of peroxide radicals formed in polytetrafluoroethylene by γ-ray irradiation

Thermal decomposition of polymer peroxide radicals formed in γ-irradiated polytetrafluoroethylene, ～CF₂CF(OO·)CF₂～ (radical I) and ～CF₂CF₂(OO～) (radical II), was studied by mass spectral analysis of the gas evolved in comparison with their photolysis with ultraviolet light. In the thermal decomposition of radicals I and II, CO₂ was the most abundant component, with smaller amount of CO, CF₂O, and gases present. In the photolysis, CO instead of CO₂ was the most abundant in the case of radical I, while in the case of radical II, CO₂ was again the main product. When a labeled polymer peroxide radical, ～CF₂CF(¹⁸O-¹⁸O·)CF₂～, was treated with heat or ultraviolet light, C¹⁸O¹⁶O was detected as a main component. In the treatment with ultraviolet light, a large amount of C¹⁸O comparable to that of C¹⁸O¹⁶O was also obtained. The mechanism of main-chain scission of radicals I and II is discussed.     

Pressure dependence of secondary ion emission from selected 3d, 4d, and 5d transition metals under N2O, NO, and NO2

The reactant gas pressure dependence of secondary ion emission from surfaces of polycrystalline Cr, Fe, Co, Mo, Rh, W, Re, and Ir under the action of N₂O, NO and NO₂ was observed by means of moderate dynamic SIMS. The mass spectra for constant reactant gas pressure indicate the existence of two different groups of transition metals showing either dissociative or partial molecular adsorption behavior. This is confirmed at least above some suitable reactant gas pressure. Besides some special details (Fe/NO; Co/NO) several of the relative secondary ion intensities vs. reactant gas pressure exhibit similar curvature as for O₂, thus indicating the NO_x gases to be modified sources of oxygen. At higher pressures molecular secondary ions with and without metal atoms come to be appreciable.     

Radiation-induced hydrogen fluoride formation in fluorine-containing ethanes and ethenes

Several fluorine-containing ethanes (monofluoro, 1,1-difluoro, 1,1,1-trifluoro, 1,1,2-trifluoro, 1,1,2,2-tetrafluoro, and pentafluoro) and ethenes (1,1-difluoro and trifluoro) form hydrogen fluoride when irradiated with gamma rays in the gas phase at 25°C. Hydrogen fluoride is apparently formed from fluoroethanes by a mechanism which involves formation of an intermediate semiion pair. We observed identical HF yields both in the absence and presence of molecular oxygen, except for monofluoroethane. A reduction of G(HF) with increasing sample pressure, for example, of 1,1,2,2-tetrafluoroethane, indicates that collisional stabilization of excited fluoroethane molecules competes with the process of HF elimination. High G values for HF and CO₂ in mixtures of CF₂?CFH and O₂ reveal the occurrence of a chain reaction.     

Pressure dependence of secondary ion emission from selected 3d, 4d, and 5d transition metals under N2O, NO, and NO2

The reactant gas pressure dependence of secondary ion emission from surfaces of polycrystalline Cr, Fe, Co, Mo, Rh, W, Re, and Ir under the action of N₂O, NO and NO₂ was observed by means of moderate dynamic SIMS. The mass spectra for constant reactant gas pressure indicate the existence of two different groups of transition metals showing either dissociative or partial molecular adsorption behavior. This is confirmed at least above some suitable reactant gas pressure. Besides some special details (Fe/NO; Co/NO) several of the relative secondary ion intensities vs. reactant gas pressure exhibit similar curvature as for O₂, thus indicating the NO_x gases to be modified sources of oxygen. At higher pressures molecular secondary ions with and without metal atoms come to be appreciable. Received: 28 May 1997 / Revised: 2 February 1998 / Accepted: 4 February 1998     

Kinetics and Mechanism of the Reaction of Xenon Tetroxide with Carbon Disulfide

The dependence of the rate of the reaction of XeO₄with CS₂on the concentrations of reactants and diluent gases He, O₂, and CO₂was studied at room temperature. A reaction mechanism was proposed.     

Molekulare Zusammensetzung von flüssigem Schwefel. Teil 2: Qualitative Analyse und Isolierung von S7, S12, α-S18 und S20

Molecular Composition of Liquid Sulfur. Part 2: Qualitative Analysis and Preparation of S₇, S₁₂, α-S₁₈, and S₂₀ from S₈ Raman spectra of sulfur melts (115–300°C), of quenched melts and of CS₂ extracts of quenched melts show besides S₈ the presence of S₆ and S₇. Formation of S₇ from S₈ at 120°C takes more than 8 h; the S₇ equilibrium concentration increases with temperature. Pure crystalline S₇, S₁₂, α-S₁₈ and S₂₀ are prepared on a preparative scale by fractional extraction, crystallization, flotation and precipitation of quenched sulfur melts. Also a mixture of larger rings (S_x; x? = 25) has been isolated. Infrared and Raman spectra of α-S₁₈, S₂₀ and S_x are reported.     

Nitration of 1,1-dichlorodifluoroethylene with nitrogen dioxide. The infrared spectra of difluoronitroacetyl chloride and 1,1-dichlorodifluoro-1,2-dinitroethane

Gas-phase nitration of CF₂CCl₂ with NO₂ at 323–353 K gave difluoronitroacetyl chloride, O₂NCF₂C(O)Cl, and 1,1-dichlorodifluoro-1,2-dinitroethane, O₂NCF₂CCl₂NO₂, which were isolated by fractional condensation and characterized by molecular weight determinations and infrared spectra. [O₂NCF₂C(O)Cl]/[O₂NCF₂CCl₂NO₂] = [k′ ([CF₂CCl₂] + γ_NO2[NO₂] + γ_P[P] + γ_X[X])]⁻¹, where k′ = 3.3±0.7x10⁻² torr⁻¹, P is the sum of the products, X = C₂F₅Cl, CCl₃F, CF₄ or N₂ and γ are the relative collisional efficiency coefficients of each gas.     

Charge inversion and neutralization–reionization mass spectra of some alkoxide ions

The charge inversion mass spectra of C₁ to C₃ alkoxide ions have been obtained using He, N₂ and O₂ as collision gases. The three collision gases show similar efficiencies for collisional charge inversion and produce similar mass spectra, although fewer high-energy oxenium ions are formed when O₂ and N₂ are used as collision gases. Using two collision cells and an intermediate deflector electrode the alkoxide ions have been neutralized in the first collision cell and the fast neutrals ionized in the second cell. The neutralization–reionization mass spectra obtained are similar to the direct charge-inversion mass spectra indicating that mainly alkoxyl radicals are produced, although, depending on the neutralization collision gas and the alkoxide ion studied, other neutrals are formed in small yields. Deuterium isotopic labelling has been used to show that the main fragmentation reactions of the unstable oxenium ions formed involve 1,1-elimination of H₂ or an alkane.     

Influence of weakly bound adduct ions on breath trace gas analysis by selected ion flow tube mass spectrometry (SIFT-MS)

This paper describes how weakly bound adduct ions form when the precursor ions used in selected ion flow mass spectrometry, SIFT-MS, analyses, viz. H₃O⁺, NO⁺ and O₂⁺, associate with the major components of air and exhaled breath, N₂, O₂ and CO₂. These adduct ions, which include H₃O⁺N₂, H₃O⁺CO₂, NO⁺CO₂, O₂⁺O₂ and O₂⁺CO₂, are clearly seen when dry air containing 5% CO₂ (typical of that in exhaled breath) is analysed using SIFT-MS. These adduct ions must not be misinterpreted as characteristic product ions of trace gases; if so, serious analytical errors can result. However, when exhaled breath is analysed these adduct ions are partly removed by ligand switching reactions with the abundant water molecules and the problems they represent are alleviated. But the small fractions of the adduct ions that remain in the SIFT-MS spectra, and especially when they are isobaric with genuine characteristic product ion of breath trace gases, can result in erroneous quantifications; such is the case for H₃O⁺N₂ interfering with breath ethanol analysis and H₃O⁺CO₂ with breath acetaldehyde analysis. However, these difficulties can be overcome when the isobaric adduct ions are properly recognised and excluded from the analyses; then these two important compounds can be properly quantified in breath. The presence of O₂⁺CO₂ in the product ion spectra interferes with the analysis of CS₂ present at low levels in exhaled breath. It is likely that similar problems will occur as other trace compounds are detected in exhaled breath when consideration will have to be given to the possibility of overlapping between their characteristic product ions and ions produced by hitherto unknown reactions. Similar problems are evident in other systems; for example, H₃O⁺CH₄ adduct ions are observed in both SIFT-MS analyses of methane rich mixtures like biologically generated waste gases and in model planetary atmospheres.     

Negative ion chemical ionization mass spectrometric studies of tetradentate schiff base coordination compounds. Fluorinecontaining reagent gases

Negative ion mass spectra using chemical ionization conditions have been measured for a series of tetradentate Schiff base corrdination compounds of Co(II), Ni(II) and Cu(II). Fluorine-containing reagent gases CF₄, SO₂F₂ and SF₆ have been used. The formation of molecular negative ions for the complexes is dependent on the reagent gas used. The secondary ions detected are produced by incorporation of CF₃, F and F₂ species into the coordination compounds.     

Gas transport properties and molecular motions of 6FDA copolyimides

The gas transport properties of 6FDA copolyimide membranes have been studied by examining their interaction such as the charge transfer complex between donor and acceptor molecules or the π–π aromatic stacking and their molecular motion in the solid-state. The interaction and the molecular motion in the membranes have been measured using fluorescence spectroscopy and solid-state ¹³C NMR spectroscopy, respectively. The gas permeability and selectivity of CO₂, O₂, N₂, and CH₄ for the membranes have been measured at 35°C and at pressures up to 10 atm. The gas permeability of the copolyimide membranes was significantly dependent on the gas diffusion, and the diffusion selectivity was a principal factor that dominates the determination of the gas selectivity in the membranes. A good correlation was found between the gas transport properties and the carbon spin–lattice relaxation time associated with the molecular motion of the CF₃ group in the copolyimide membranes.     

Vacuum UV laser-induced fluorescence study of the collisional removal of Br(P1/2) atoms by small molecules

This Letter reports on the application of the vacuum ultraviolet laser-induced fluorescence detection of Br(²P_1/2) atoms at 157.48 nm to the kinetic study of collisional removal of Br(²P_1/2) by small molecules at 295 K. Gas mixtures of a small amount of CH₃Br and an excess amount of collision partners are exposed to pulsed laser irradiation at 193 nm. Temporal decay profile of the Br* LIF intensity has been monitored to determine the collisional removal rate coefficients. The collision partners are H₂, CO₂, CF₄, CF₂H₂, H₂O, CH₃OH, and SF₅CF₃, and the results are compared to literature data.     

The infrared spectra of gaseous 1,1,3,3-tetrachlorotetrafluoro-4-(trifluoromethyldioxy)butyl trifluoromethyl ether and 1,1,3,3-tetrachlorotetrafluoro-1,4-bis(trifluoromethoxy)butane

1,1,3,3-Tetrachlorotetrafluoro-4-(trifluoromethyldioxy)butyl trifluoromethyl ether, CF₃O(CF₂CCl₂)₂O₂CF₃, was formed as one of the products in the reaction of CF₃O₃CF₃ with CF₂CCl₂ at 322.6 - 342.5 K. It was isolated by fractional condensation between 213 and 243 K and characterized by molecular weight determination and ¹⁹F NMR spectrum. 1,1,3,3-Tetrachlorotetrafluoro-1,4-bis(trifluoromethoxy)butane, CF₃O(CF₂CCl₂)₂OCF₃, was condensed as residue at 193 K from the reaction of CF₃OF with CF₂CCl₂ at 266 - 302.7 K, when [CF₂CCl₂]/[CF₃OF] ≦ 0.5. It was characterized by gas chromatography and molecular weight determination. The infrared spectra of both compounds are given, providing additional support for their characterization.     

Synthesis of (CH3C(CH2PPh2)3)CoL complexes (L = O2CO,S2CO,O2SO) through metal-assisted CO2, CS2, SO2 oxidation. Crystal structure of (CH3C(CH2PPh2)3)CO(O2SO)

The solution obtained by reduction of [(triphos)CO(μ-Cl)₂Co(triphos)]⁺² (triphos = CH₃C(CH₂PPh₂)₃) with Na/Hg reacts with CO₂, CS₂ and SO₂ to give (triphos)Co(O₂CO), (triphos)Co(S₂CO), and (triphos)Co(O₂SO), respectively. The molecular structure of the last has been established by X-ray difraction.     

Wavelength-resolved fluorescence lifetimes of gas-phase ions: CO2+ and CS2+

A method is described for measuring wavelength-resolved fluorescence lifetimes of ions formed by HeIα photoionization, using electric-field drift of the ions in competition with fluorescence. Fluorescence lifetimes of 216 and 232 ns for the 357 nm and 378 nm peaks of N₂O⁺, and 3.5 μs for the à → X? band of CS₂⁺, were measured. The wavelength-resolved à → X? band of CO₂⁺ showed no significant dependence of fluorescence lifetime on V′, but there is some indication of variation in the CS₂⁺ lifetimes in the à → X? band.     

The thermal properties of inorganic compounds: II. Evolved gas studies of some mercury(I) and (II) compounds

The combined thermal analysis techniques of thermogravimetry, evolved gas analysis and mass spectrometry were used to investigate the thermal decomposition of several selected mercury(I), (II) compounds. Although TG curves are presented, the analysis of the evolved gases formed during the thermal decomposition processes was of greater interest. Gaseous products detected included: HgSO₄SO, SO₂ and O₂; Hg(SCN)₂CS₂, (CN)₂ and N₂; Hg(NO₃)₂NO, N₂O, NO₂ and O₂; HgNO₃ H₂ONO, NO₂ and N₂O; and Hg(C₂H₃O₂)₂—organic fragments. The evolved gas analysis was complicated by sublimation of the compounds at low pressures.     

Towards insight into properties and stabilities of complexes of ozone with CO2, CS2 and SCO species

The MP2 method in combination with the aug-cc-pVXZ (X = D and T) basis set has been carried out to examine the complexes between O₃ and isostructure species of CO₂, CS₂ and SCO. Two, two and four minima have been located on the potential energy surfaces of O₃–CO₂, O₃–CS₂ and O₃–SCO complexes, respectively. The results reveal that the stabilization of complexes should be in the order O₃–CS₂ > O₃–SCO > O₃–CO₂.     

ω-hydro-perfluoroalkyl pyrimidinyl nitroxides

Twenty-two polysubstituted 2-aminopyrimidines dissolved in F1 13 (CC1F₂-CCl₂F) solutions containing ([H(CF₂CF₂)_nCO₂]₂ n = 1,2) and H(CF₂CF₂)_nNO [? H(CF₂CF₂)_n ^? + NO] have been oxidized into detectable ω-H-perfluoroalkyl pyrimidinyl nitroxides along with neutral products. A mechanism involving Habstraction from the amino groups by H(CF₂CF₂)_nN(O^?)(CF₂CF₂)_nH and the subsequent radical steps was suggested for the generation of the nitroxides. Some relationships between a_N values and the nature of the ring substituents are discussed.