Photolysis of sulfur dioxide in the presence of foreign gases: VII. Acetylene

SO₂ was photolyzed at 25°C and 3130 Å in the presence of acetylene. The quantum yield of the sole gas-phase product, CO, was determined for a wide range of SO₂ and C₂H₂ pressures, and in the presence of CO₂, NO and H₂O. The quantum yield, Φ{CO}, increases with the ratio [C₂H₂] [SO₂] to an upper limiting value of 0.052. In the presence of excess CO₂ or H₂O vapor, Φ{CO}becomes independent of [SO₂] and is reduced at low values of [C₂H₂] but remains unchanged or increases slightly at high values of [C₂H₂]. As NO is added at the higher C₂H₂ pressures it first increases Φ{CO} but then reduces it to zero. None of the CO comes from singlet states as shown by the strong quenching of CO production by NO. Both of the two non-emitting triplet states previously proposed to be important in the photochemistry of SO₂, as well as the emitting triplet, are necessary to interpret the results of this study. A relatively complete mechanism is presented, all the pertinent rate coefficient ratios are obtained, and from these, values of Φ{CO} are computed. They agree well with the observed values.     

Studies of the photochemical reactions of sulfur dioxide with pentane in the presence of nitrogen oxide

The spectrum of the intermediate product ascribed to nitrosopentane has been detected in the photolysis of the SO₂–pentane (RH)–NO mixture. This result has been interpreted in terms of the radical mechanism by assuming the H-atom abstraction from RH by the excited SO₂ molecules to be the primary act. The contribution of the singlet and triplet SO₂ states to the product formation rate and the ratio of the singlet-to-triplet rate constants have been evaluated. At NO pressures above 5 torr, the product formation rate significantly deviates from the Stern–Volmer dependence.     

Role of silica-alumina catalyst texture in the reaction of propane oxidative dehydrogenation in the presence of sulfur dioxide

The effects of preparation conditions, component ratio, and pretreatment temperature (1000–1550‡C) of silica-alumina samples on their phase composition, texture characteristics, and catalytic properties are studied in the reaction of the oxidative dehydrogenation of propane by sulfur dioxide. It is shown that the samples contain individual silicon and aluminum oxides. The product of their interaction (mullite) is formed only at 1550°C. Mesoporous and macroporous catalysts with monoand polydispersed pore distributions over sizes are obtained. It is found that the porous structure of the catalyst plays a key role in the process of the oxidative dehydrogenation of propane in the presence of sulfur dioxide at 600–700°C. The apparent rate of propylene formation increases with an increase in the pore volume with radii between 10 and 100 nm. Propane is transformed into propylene more selectively on the catalyst where the pores with radii of 10–100 nm dominate; narrower pores (< 10 nm) are favorable for the formation of coke and complete oxidation products.     

Dilation of polycarbonate by carbon dioxide

A new technique is described for dilatometry under high pressure. The technique is based on optical interferometry and is analogous to measuring the thickness of thin, nonabsorbing films and coatings. The procedure is demonstrated for the well-characterized system of n-pentane sorption by polyisobutylene, and then results for the dilation of polycarbonate by the sorption of carbon dioxide are presented. The dilation of polycarbonate by CO₂ is nearly linear with concentration; the partial molar volume of CO₂ decreases slightly with increasing pressure. This result indicates that all sorbed CO₂ molecules contribute equally to the dilation of the polymer matrix and that none reside in microvoids or in preexisting free-volume elements which do not contribute to volume expansion of the polymer.     

A specific spectrophotometric determination of ozone in air in the presence of sulfur dioxide and nitrogen oxides

A sensitive, specific spectrophotometric method for the determination of ozone in air by the ozonolysis of 1,1-di-phenylethylene (DPE) is described. The yield of formaldehyde from the ozonolysis of several terminal olefins was determined, and DPE was found to give the highest yield, 90%. The method was checked against the EPA iodimetric method, and gives a consistent yield of formaldehyde over the ozone range 0.05–5.00 μg g^-1 of air. As sulfur dioxide is used as a reagent, its presence in air does not interfere. Interference by nitrogen oxides and other free radical oxidants is prevented by the addition of mesitol (2,4,6-trimethylphenol). Formaldehyde in air interferes, but can be determined by using the method with DPE omitted from the sampling train, and so accounted for. In the procedure, formaldehyde is determined by the reverse of the West—Gaeke method for sulfur dioxide.     

Carbon dioxide sorption and transport in polycarbonate

The solubility, permeability, and diffusion time lag for carbon dioxide in polycarbonate are reported at 35°C for pressures ranging from 1 atm to 23 atm. The solubility data are very well described by the dual sorption mechanism model, Henry's law plus Langmuir adsorption, proposed for glassy polymers. Both the permeability and time lag decrease with increased CO₂ pressure. These observations are not consistent with the proposal that CO₂ sorbed by the Langmuir contribution is totally immobilized; however, all of the results are entirely consistent with an extension of this proposal which considers partial immobilization. The data have been quantitatively analyzed in terms of this partial immobilization model, and the results suggest for polycarbonate at 35°C that the CC₂ sorbed by the Langmuir portion of the isotherm behaves as if it has only about 10% of the mobility of the gas sorbed by the Henry's law part of the isotherm. The results have also been interpreted in terms of a concentration-dependent diffusion coefficient which is shown to be mathematically equivalent to the partial immobilization model. The latter model was also formulated in thermodynamic terms, whereby fugacity was used rather than pressure, and diffusion coefficients were defined in terms of chemical potential gradients rather than concentration, but the consequences of these changes proved to be minor and no better. The significance of these observations and their interpretation is discussed.     

Determination of phenol in the presence of sulfite (sulfur dioxide) by the 4-aminoantipyrine spectro-photometric method

The interference of sulfite (sulfur dioxide) with the 4-aminoantipyrine (4-AAP) spectrophotometric method for phenol is discussed for procedures without distillation, and with distillation in the absence and presence of copper(II) sulfate. Sulfite represses the color development in all these procedures. Without chloroform extraction, the maximum tolerable amounts of sulfite in the procedures without distillation, distillation without copper(II) sulfate, and distillation with copper(II) sulfate are 15, 10, and 20 mg/100 ml, respectively. For the extraction method, the limits are 4.0, 4.0, and 10 mg/ 100 ml, respectively. Copprer(II) sulfate catalyzes the air-oxidation of sulfite. Phenol can be determined in the presence of large amounts of sulfite by treating with sulfide to form polythionates and thiosulfate; excess of sulfide is removed with copper(II) sulfate, sulfuric acid is added, the phenol is distilled, and the 4-AAP method is applied. Improvements are made in the overall accuracy of the 4-AAP method.     

Determination of sulfur dioxide in air

The determination of sulfur dioxide in air is based on a preliminary purification with a cellulose filter and 80% isopropanol and absorption of sulfur dioxide by means of two midget impingers in 0.3 N hydrogen peroxide. The formed sulfate is titrated in an aliquot with 0.005 M barium perchlorate employing Chlorophosphonazo III (CPA) as an indicator. The method is suitable for 0.3–19.0 mg of sulfur dioxide per 50 liters of air. The standard deviation of the titration is ±0.02 ml per consumption of 5.00 ml and is four times smaller than that of the Thorin method.     

Reaction of 1,1-dichloro-1-nitrosoalkanes with the acid chloride of S-ethylmethylphosphorous acid in the presence of sulfur dioxide

1,1-Dichloro-1-nitrosoalkanes react exothermally with the acid chloride of S-ethylmethylphosphorous acid to give O-alkylchloroformiminophosphoranes, which are converted in the presence of SO₂ to O-alkylchloroformimino-S-ethylmethylphosphonates.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 464–465, February, 1990.     

Molecular basis of carbon dioxide transport in polycarbonate membranes

Gas transport of carbon dioxide in poly[bisphenol A carbonate-co-4,4'-(3,3,5-trimethylcyclohexylidene)diphenol carbonate] films over a wide range of pressure is described. The interpretation of the experimental results in terms of the dual mode model allowed the evaluation of the parameters of the model that govern the gas permeation process. The value of the diffusion coefficient obtained for carbon dioxide at zero concentration was 2.4 x 10(-8) cm(2) s(-1), at 303 K. This parameter was also measured by using pulsed field gradient NMR finding that its value reaches a nearly constant value of (2.7 +/- 0.9) x 10(-8) cm(2) s(-1), at 298 K, for diffusion times greater than 20 ms. Both the diffusion and solubility coefficients were also computed by using simulation methods based on the transition states theory and the Widom method, respectively. The value obtained for the diffusion coefficient was 1.8 x 10(-8) cm(2) s(-1), at 303 K, which compares very favorably with the experimental measurements. The drop of the simulated solubility coefficient with increasing pressure is sharper than that of the experimental one, at low pressures, and similar, at high pressures.     

Catalytic transformations of sulfur dioxide into organic sulfur compounds

The applications of catalytic transformations of SO₂ into sulfur-containing organic compounds, reported in the literature, are briefly reviewed. The authors' studies in this field of chemistry,viz., the hydrosulfination of alkenes, the synthesis of γ-oxo sulfonesvia hydrosulfination, and the synthesis of aromatic sulfinic acids from diazonium salts, are summarized. Current results on the synthesis of the new sulfinato complex [Pd(SO₂Ph)(Cl)dppp] and its hydrogenation to PhSO₂H are presented, and a mechanism for the catalytic synthesis of sulfinic acids is proposed. The structure of ([Pd(μ-Cl)(dppp)l₂ ²⁺(SO₄)^2?·4SO₂ salt is studied by X-ray diffraction analysis.     

The photolysis of sulfur dioxide in the presence of foreign gases XII: Photolysis of SO2 at 313.0 nm in the presence of both allene and oxygen

SO₂ was photolyzed at 25 °C and 313.0 nm in the presence of allene and oxygen. The quantum yields of the gas phase products CO and C₂H₄ were determined over a wide range of allene and oxygen pressures as well as in the presence and absence of 600 Torr of CO₂. The quantum yield Φ {CO} of CO increased at constant [allene]/[SO₂] ratios with the addition of O₂ up to pressures of 1 – 30 Torr depending upon the [allene]/[SO₂] ratio. With further increases in O₂ pressure, Φ {CO} was quenched. The quantum yield Φ {C₂H₄} of C₂H₄ exhibited similar behavior. The addition of 600 Torr of CO₂ appeared to have little effect upon either the enhancement or quenching of Φ {CO}. The addition of increasing amounts of CO₂ to a constant [allene]/[SO₂]/[O₂] ratio decreased Φ {C₂H₄} to a limiting value of approximately 4 × 10⁻³ at 600 Torr of CO₂. Both the singlet and triplet emitting states as well as two non-emitting states of SO₂ previously proposed to be important in the photochemistry of SO₂ are necessary to interpret the results of this study. A relatively complete mechanism is proposed, all the pertinent rate coefficients are tabulated, and from these values Φ {CO} and Φ {C₂H₄} values are computed and compared with the observed values. The proposed mechanism is found to underestimate total Φ {C₂H₄} at low allene and high O₂ pressures. There must be an additional source of C₂H₄ which is not included in the mechanism.     

The Gas-Solid Interface the adsorption of nitrogen,argon, neopentane,sulfur dioxide,carbon dioxide and sulfur hexafluoride on rhombic sulfur

Physical adsorption of the title compounds on rhombic sulfur of 0.4 to 0.5 m²/g is reported. The isotherms are of type II for N₂, Ar and C₅H₁₂, of type III for SO₂ and CO₂, and linear for SF₆. There is no hysteresis. The method of Ross & Olivier shows that the surface is relatively heterogenous (γ 17). Isosteric heats of adsorption and c values of the B.E.T. equation are also reported.     

Phenylation of sulfur dioxide by pentaphenylbismuth

Conclusions Pentaphenylbismuth phenylates sulfur dioxide to give diphenylsulfone under mild conditions in high yield.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2598–2599, November, 1987.