Sulfur Dioxide Solution Research Articles

Homopolyatomic Chalcogen Radical Cations of Selenium and Tellurium

The stability of selenium and tellurium homopolyatomic radical cations in the gas phase and liquid sulfur dioxide solution was estimated using density functional theory (DFT). First of all, the structures of the neutral, cationic, and dicationic homopolyatomic chalcogen clusters [Chx]y+ (Ch = Se, Te; x = 3–10, y = 0–2) were optimized in the gas phase. The stability of the currently unknown radical cations [Chx]+ against various decomposition reactions (e.g. disproportionation, dimerization) was predicted by estimating the reaction enthalpies and free energies in the gas phase and in liquid sulfur dioxide solution applying a solvation model. The solvent SO2 was chosen, because homopolyatomic chalcogen cations react immediately with most common organic solvents but are known to be stable in liquid sulfur dioxide. A significant stability in solution was predicted only for the radical cations [Se5]+ and [Se8]+, while [Te8]+ is a borderline case. In the course of our investigations the previously unknown dications [Ch5]2+ were calculated as well, which have a triplet rather than a singlet ground state similar to the three‐atomic [S3]2+ dication.

Mathematical model of liquid sulfur dioxide injection into layer saturated with water and methane

The mathematical model of sulfur dioxide solution injection into the layer saturated with the water and methane accompanied by formation of sulfur gas hydrate is presented. For the axisymmetric problem, self-similar solutions describing the distribution of temperature and pressure in the layer are constructed. It is established that depending on the mass flow rate of sulfur dioxide injection, the formation of sulfur dioxide gas hydrate can occur both on the front surface and in the extended region. There are determined the limit values of the mass flow rate of sulfur dioxide injection separating different modes of sulfur dioxide gas hydrate formation. It is established that the mode with the gas hydrate formation of sulfur dioxide in an extended region is realized at high values of mass injection flow rate of sulfur dioxide and of the initial temperature of the layer.

ChemInform Abstract: Perfluoroalkylation of Nitrones for the Synthesis of a Series of Fucosidase Inhibitors.

Fucosidase inhibitors represent captivating targets for various biological applications. Iminosugars featuring a fluoroalkyl chain in the pseudoanomeric position were synthesized by nucleophilic addition of a perfluoroalkyl Grignard reagent to a nitrone. Reduction of the N–O bond of the hydroxylamine was achieved by treatment with an aqueous solution of sulfur dioxide. The pKa = 4.5 of the target pyrrolidine reflected a strong electronic effect of the fluoroalkyl chain. Inhibitory potencies of the fluorinated iminosugars and their corresponding hydroxylamines were evaluated against α-L-fucosidase at various pH values.

Perfluoroalkylation of Nitrones for the Synthesis of a Series of Fucosidase Inhibitors

AbstractFucosidase inhibitors represent captivating targets for various biological applications. Iminosugars featuring a fluoroalkyl chain in the pseudoanomeric position were synthesized by nucleophilic addition of a perfluoroalkyl Grignard reagent to a nitrone. Reduction of the N–O bond of the hydroxylamine was achieved by treatment with an aqueous solution of sulfur dioxide. The pKa = 4.5 of the target pyrrolidine reflected a strong electronic effect of the fluoroalkyl chain. Inhibitory potencies of the fluorinated iminosugars and their corresponding hydroxylamines were evaluated against α‐L‐fucosidase at various pH values.

English

Fruits have abundant phytochemicals that contribute as bioactive molecules with ability to lower incidence of diseases. Mangoes are rich in polyphenols and antioxidants. In this study, peels of six selected mango cultivars (Tommy Atkins, Peach, Saber, Sunshine, Keitt and Vhavenda) were treated with sulphur dioxide solutions (0, 10, 20, 50, 100, 150, 200, 250 and 300 ppm) as preservative of phytochemicals and antioxidants capacity. Regardless of cultivar, sulphur concentration had effect on composition of polyphenols and antioxidant capacity of mango peels, reaching a plateau at 50 ppm. Vhavenda cultivar has significantly highest polyphenols and antioxidant capacity than the other cultivars evaluated. This study reveals that mango peels are a prospective source of natural antioxidants as they constitute significantly higher total antioxidant capacity and phenolic content. Key words: Antioxidants, mango cultivars, peels, phytochemicals, sulphur.

Effects of the mechanical damage on the water absorption process by corn kernel

Abstract The purpose of this study was to investigate and model the water absorption process by corn kernels with different levels of mechanical damage Corn kernels of AG 1510 variety with moisture content of 14.2 (% d.b.) were used. Different mechanical damage levels were indirectly evaluated by electrical conductivity measurements. The absorption process was based on the industrial corn wet milling process, in which the product was soaked with a 0.2% sulfur dioxide (SO 2 ) solution and 0.55% lactic acid (C 3 H 6 O 3 ) in distilled water, under controlled temperatures of 40, 50, 60, and 70 °C and different mechanical damage levels. The Peleg model was used for the analysis and modeling of water absorption process. The conclusion is that the structural changes caused by the mechanical damage to the corn kernels influenced the initial rates of water absorption, which were higher for the most damaged kernels, and they also changed the equilibrium moisture contents of the kernels. The Peleg model was well adjusted to the experimental data presenting satisfactory values for the analyzed statistic parameters for all temperatures regardless of the damage level of the corn kernels.

NO][HCB11Cl11] – Synthesis, Characterization, Crystal Structure, and Reaction with P4

AbstractThe thermodynamic stability of the [HCB11Cl11]– salts of the cationic one‐electron oxidizers [NO]+ and [O2]+ was estimated by Born–Haber–Fajans cycles based on quantum‐chemical calculations and lattice enthalpy estimations. [NO][HCB11Cl11] is predicted to be a stable compound, whereas [O2][HCB11Cl11] should decompose into O2 and the HCB11Cl11· radical. Consequently, [NO][HCB11Cl11] can be prepared by metathesis reaction from Na[HCB11Cl11] and [NO][BF4] in liquid sulfur dioxide, while attempts to synthesize [O2][HCB11Cl11] failed. [NO][HCB11Cl11] has been fully characterized by NMR and vibrational spectroscopy. Single crystals of [NO][HCB11Cl11]·SO2 were obtained from liquid sulfur dioxide solution. The crystal structure determination revealed several intermolecular cation–anion contacts, which are significantly shorter than the sum of the van der Waals radii of the respective atoms. [NO][HCB11Cl11] reacts with white phosphorus in CH2Cl2 solution to give yellow‐orange [P4NO][HCB11Cl11] containing the [P4NO]+ cation. An in‐situ NMR spectroscopic study indicates the presence of the homopolyatomic phosphorus cation [P9]+ in the reaction mixture.

ChemInform Abstract: Identification of S2O4 in Sulfur Dioxide Solutions in HMPA.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis, Crystal Structure, and Reactivity of the Strong Methylating Agent Me2B12Cl12

Synthesis, Crystal Structure, and Reactivity of the Strong Methylating Agent Me₂B₁₂Cl₁₂

Sulfur X-ray Absorption and Vibrational Spectroscopic Study of Sulfur Dioxide, Sulfite, and Sulfonate Solutions and of the Substituted Sulfonate Ions X3CSO3- (X = H, Cl, F)

Sulfur K-edge X-ray absorption near-edge structure (XANES) spectra have been recorded and the S(1s) electron excitations evaluated by means of density functional theory-transition potential (DFT-TP) calculations to provide insight into the coordination, bonding, and electronic structure. The XANES spectra for the various species in sulfur dioxide and aqueous sodium sulfite solutions show considerable differences at different pH values in the environmentally important sulfite(IV) system. In strongly acidic (pH < approximately 1) aqueous sulfite solution the XANES spectra confirm that the hydrated sulfur dioxide molecule, SO2(aq), dominates. The theoretical spectra are consistent with an OSO angle of approximately 119 degrees in gas phase and acetonitrile solution, while in aqueous solution hydrogen bonding reduces the angle to approximately 116 degrees . The hydration affects the XANES spectra also for the sulfite ion, SO32-. At intermediate pH ( approximately 4) the two coordination isomers, the sulfonate (HSO3-) and hydrogen sulfite (SO3H-) ions with the hydrogen atom coordinated to sulfur and oxygen, respectively, could be distinguished with the ratio HSO3-:SO3H- about 0.28:0.72 at 298 K. The relative amount of HSO3- increased with increasing temperature in the investigated range from 275 to 343 K. XANES spectra of sulfonate, methanesulfonate, trichloromethanesulfonate, and trifluoromethanesulfonate compounds, all with closely similar S-O bond distances in tetrahedral configuration around the sulfur atom, were interpreted by DFT-TP computations. The energy of their main electronic transition from the sulfur K-shell is about 2478 eV. The additional absorption features are similar when a hydrogen atom or an electron-donating methyl group is bonded to the -SO3 group. Significant changes occur for the electronegative trichloromethyl (Cl3C-) and trifluoromethyl (F3C-) groups, which strongly affect the distribution especially of the pi electrons around the sulfur atom. The S-D bond distance 1.38(2) A was obtained for the deuterated sulfonate (DSO3-) ion by Rietveld analysis of neutron powder diffraction data of CsDSO3. Raman and infrared absorption spectra of the CsHSO3, CsDSO3, H3CSO3Na, and Cl3CSO3Na.H2O compounds and Raman spectra of the sulfite solutions have been interpreted by normal coordinate calculations. The C-S stretching force constant for the trichloromethanesulfonate ion obtains an anomalously low value due to steric repulsion between the Cl3C- and -SO3 groups. The S-O stretching force constants were correlated with corresponding S-O bond distances for several oxosulfur species.

Simultaneous solubility of SO 2 and NH 3 in (salt + H 2O) and enthalpy change upon dilution of (SO 2 + NH 3 + salt + H 2O) in (salt + H 2O) {salt = (NH 4) 2SO 4 or Na 2SO 4}: Experimental results and model predictions

The simultaneous solubility of sulfur dioxide and ammonia in aqueous solutions of (ammonium sulfate or sodium sulfate) was measured by a synthetic method in the temperature range from 313.6 to 373.2 K and at pressures up to 2.5 MPa. Furthermore, the enthalpy change upon diluting aqueous solutions of sulfur dioxide, ammonia and (ammonium sulfate or sodium sulfate) in aqueous solutions of the same salt was measured in a batch calorimeter at about 313 and 352 K. The experimental results are used for comparison with predictions from a thermodynamic model for the vapor–liquid equilibrium and the enthalpy of dilution of those chemical reacting systems. In that model, activity coefficients are calculated from Pitzer's molality-scale-based Gibbs excess energy model, where all interaction parameters are either adopted from previous investigations on the properties of the binary and ternary sub-systems (if available) or they are neglected (if they are not available).

Enthalpy of dilution of [SO 2 + salt + H 2O] in [salt + H 2O] {salt = (NH 4) 2SO 4 or Na 2SO 4}: Experimental results and modeling

New experimental results are presented for the enthalpy change upon diluting aqueous solutions of sulfur dioxide containing a salt (either ammonium sulfate or sodium sulfate) in aqueous solutions of that salt at about 313 and 352 K. A previously developed thermodynamic model for the vapor–liquid equilibrium of the chemical reacting systems {SO 2 + (NH 4) 2SO 4 + H 2O} and (SO 2 + Na 2SO 4 + H 2O) is extended allowing for the formation of pyrosulfite and for the description of the new experimental results for the enthalpy change upon dilution.

Enthalpy of dilution of (SO 2 + H 2O) and (SO 2 + NH 3 + H 2O) in pure water: experimental results and modeling

New experimental results for the enthalpy change upon diluting aqueous solutions of sulfur dioxide as well as aqueous solutions of sulfur dioxide and ammonia in pure water at about 313 and 352 K are presented. The experimental results are used to modify a previously developed thermodynamic model for the vapor–liquid equilibrium of the chemical reacting system (SO 2 + NH 3 + H 2O). That model is extended allowing on the one side for the formation of pyrosulfite, and on the other side for the description of experimental results for the enthalpy change upon dilution (in pure water) of (NH 3 + H 2O) (taken from the literature), as well as (SO 2 + H 2O) and (SO 2 + NH 3 + H 2O) (from the present work).

Evidence for the blue 10 pi S62+ dication in solutions of S8(AsF6)2: a computational study including solvation energies.

The energetics of dissociation reactions of S(8)(2+) into stoichiometric mixtures of S(n)(+), n = 2-7, and S(m)(2+), m = 3, 4, 6, 10, were investigated by the B3PW91 method [6-311+G(3df)//6-311+G] in the gas phase and in solution, with solvation energies calculated using the SCIPCM model and in some cases also the COSMO model [B3PW91/6-311+G*, dielectric constants 2-30, 83, 110]. UV-vis spectra of all species were calculated at the CIS/6-311G(2df) level and for S(4)(2+) and S(6)(2+) also at the TD-DFT level (BP86/SV(P)). Standard enthalpies of formation at 298 K were derived for S(3)(2+) (2538 kJ/mol), S(6)(2+) (2238 kJ/mol), and S(10)(2+) (2146 kJ/mol). A comparison of the observed and calculated UV-vis spectra based on our calculated thermochemical data in solution suggests that, in the absence of traces of facilitating agent (such as dibromine Br(2)), S(8)(2+) dissociates in dilute SO(2) solution giving an equilibrium mixture of ca. 0.5S(6)(2+) and S(5)(+) (K approximately 8.0) while in the more polar HSO(3)F some S(8)(2+) remains (K approximately 0.4). According to our calculations, the blue color of this solution is likely due to the pi-pi transition of the previously unknown 10 pi S(6)(2+) dication, and the previously assigned S(5)(+) is a less important contributor. Although not strictly planar, S(6)(2+) may be viewed as a 10 pi electron Hückel-aromatic ring containing a thermodynamically stable 3p(pi)-3p(pi) bond [d(S-S) = 2.028 A; tau(S-S-S-S) = 47.6 degrees ]. The computations imply that the new radical cation S(4)(+) may be present in sulfur dioxide solutions given on reaction of sulfur oxidized by AsF(5) in the presence of a facilitating agent. The standard enthalpy of formation of S(6)(AsF(6))(2)(s) was estimated as -3103 kJ/mol, and the disproportionation enthalpy of 2S(6)(AsF(6))(2)(s) to S(8)(AsF(6))(2)(s) and S(4)(AsF(6))(2)(s) as exothermic by 6-17 kJ/mol. The final preference of the observed disproportionation products is due to the inclusion of solvent molecules, e.g., AsF(3), that additionally favors the disproportionation of 2S(6)(AsF(6))(2)(s) into S(8)(AsF(6))(2)(s) and S(4)(AsF(6))(2)(AsF(3))(s) by 144 kJ/mol.

The reaction of Li[Al(OR)4] R = OC(CF3)2Ph, OC(CF3)3 with NO/NO2 giving NO[Al(OR)4], Li[NO3] and N2O. The synthesis of NO[Al(OR)4] from Li[Al(OR)4] and NO[SbF6] in sulfur dioxide solution.

NO[Al(OC(CF(3))(2)Ph)(4)] 1 and NO[Al(OC(CF(3))(3))(4)] 2 were obtained by the metathesis reaction of NO[SbF(6)] and the corresponding Li[Al(OR)(4)] salts in liquid sulfur dioxide solution in ca 40% (1) and 85% (2) isolated yield. 1 and 2, as well as Li[NO(3)] and N(2)O, were also given by the reaction of an excess of mixture of (90 mol%) NO, (10 mol%) NO(2) with Li[Al(OR)(4)] followed by extraction with SO(2). The unfavourable disproportionation reaction of 2NO(2)(g) to [NO](+)(g) and [NO(3)](-)(g)[DeltaH degrees = +616.2 kJ mol(-1)] is more than compensated by the disproportionation energy of 3NO(g) to N(2)O(g) and NO(2)(g)[DeltaH degrees =-155.4 kJ mol(-1)] and the lattice energy of Li[NO(3)](s)[U(POT)= 862 kJ mol(-1)]. Evidence is presented that the reaction proceeds via a complex of [Li](+) with NO, NO(2)(or their dimers) and N(2)O. NO(2) and Li[Al(OC(CF(3))(3))(4)] gave [NO(3)(NO)(3)][Al(OC(CF(3))(3))(4)](2), NO[Al(OC(CF(3))(3))(4)] and (NO(2))[Al(OC(CF(3))(3))(4)] products. The aluminium complex [Li[AlF(OC(CF(3))(2)Ph)(3)]](2) 3 was prepared by the thermal decomposition of Li[Al(OC(CF(3))(2)Ph)(4)]. Compounds 1 and 3 were characterized by single crystal X-ray structural analyses, 1-3 by elemental analyses, NMR, IR, Raman and mass spectra. Solid 1 contains [Al(OC(CF(3))(2)Ph)(4)](-) and [NO](+) weakly linked via donor acceptor interactions, while in the SO(2) solution there is an equilibrium between the associated [NO](+)[Al(OC(CF(3))(2)Ph)(4)](-) and separated solvated ions. Solid 2 contains essentially ionic [NO](+) and [Al(OC(CF(3))(3))(4)](-). Complex 3 consists of two [Li[AlF(OC(CF(3))(2)Ph)(3)]] units linked via fluorine lithium contacts. Compound 1 is unstable in the SO(2) solution and decomposes to yield [AlF(OC(CF(3))(2)Ph)(3)](-), [(PhC(CF(3))(2)O)(3)Al(mu-F)Al(OC(CF(3))(2)Ph)(3)](-) anions as well as (NO)C(6)H(4)C(CF(3))(2)OH, while compound 2 is stable in liquid SO(2). The [small nu](NO(+)) in 1 and [NO](+)(toluene)[SbCl(6)] are similar, implying similar basicities of [Al(OC(CF(3))(2)Ph)(4)](-) and toluene.

A mixed surface reaction kinetic model for the reductive leaching of manganese dioxide with acidic sulfur dioxide

Previous researchers have rationalised the kinetics of dissolution of manganese dioxide in acidic sulfur dioxide solutions on the basis of either the adsorption of reactants followed by reactions with HSO 3 − and SO 2 or a two-electron surface electrochemical reaction with H + and HSO 3 −, the species involved in the equilibrium: SO 2(aq)+H 2O=H ++HSO 3 −. This paper revisits the reported rate data for the dissolution of MnO 2 in the form of plates [Herring and Ravitz, Trans. SME/AIME 231 (1965) 191] or particles [Miller and Wan, Hydrometallurgy 10 (1983) 219] to show that the rate of dissolution can be rationalised on the basis of a fast redox reaction : (i) MnO 2(s)+SO 2(aq)+H 2O=MnOOH(s)+HSO 3(aq) followed by one of the two rate determining redox reactions: (ii) MnOOH(s)+HSO 3(aq)=MnSO 4 0(aq)+H 2O or Mn(OH)HSO 4(s), (iii) MnOOH(s)+SO 2(aq)=MnO(s)+HSO 3(aq) depending on the pH of the medium. Whilst the rate equation for (iii) agrees with the electrochemical kinetic model reported previously, the dissolution of the solid Mn(OH)HSO 4 or the direct reaction: (iv) MnO 2(s)+SO 2(aq)=MnSO 4 0(aq) also appear to be rate controlling. The two rate constants k 1 and k 2 based on a shrinking sphere kinetic model: 1−(1− X) 1/3= k 1 K 0.5[SO 2] 0.5( t/ rρ)+ k 2[SO 2]( t/ rρ), for the leaching of monosized pyrolusite and electrolytically prepared MnO 2 particles, are in reasonable agreement with k 1 and k 2 based on the dissolution kinetics of MnO 2 plates.

Sonoluminescence of aqueous solutions of sulfuric acid and sulfur dioxide

Sonoluminescence (SL) of aqueous solutions of sulfuric acid and sulfur dioxide enhances with an increase in their concentration and reaches a maximum at 16 and 0.05 mol L–1, respectively. The further increase in the concentration of these substances decreases the SL intensity. The SL spectra of the solutions have a broad maximum at 450 nm. Excited SO2 molecules formed in sulfuric acid due to sonolysis are luminescence emitters. The proposed mechanism of bright SL in these systems is based on the energy transfer from the electron-excited sonolysis products to the SO2 molecules in cavitation bubbles.

Study of some factors affecting water absorption by amaranth grain during soaking

Water absorption by amaranth grain in plain water was determined at 30, 40, 50 and 60 °C by recording the weight increase in grain with respect to time. Water absorption kinetics at these temperatures was described by the Fick’s second law solution for diffusion out of sphere. Effective diffusion coefficients varied between 2.63 and 8.25 × 10 −12 m 2/s for the range investigated. The activation energy for diffusion obtained was 32.1 kJ mol −1. The rates of absorption in SO 2 aqueous solution (0.01%, 0.02% and 0.03%, v/v) were slightly higher than in plain water at 40 and 60 °C. However, the increase in SO 2 concentration did not seem to increase significantly water absorption. Amaranth grain soaked in 0.02% (v/v) SO 2 aqueous solution and variable lactic acid concentrations (0.0025% and 0.0050%, v/v) was performed at 40 °C. Absorption rates for lactic acid concentrations were ≈9.1% higher than those steeped only in SO 2 aqueous solution; lactic acid concentration had no effect on the absorption rate. The amount of total solids leached in sulfur dioxide solution with lactic acid (200 ppm SO 2 + 0.005% lactic acid) was the highest when compared with the other steeping media investigated.

Electrochemical behavior of stainless steel W.Nr. 1.4301 in the malic acid and sulfur dioxide solution

In our earlier investigation on stainless steel W.Nr. 1.4301, corrosion damage was observed when the steel was in the contact with fruit pulps and pectin which had been conserved with SO 2. In order to understand the corrosion behavior of stainless steel W.Nr. 1.4301, which is used in equipment for the production and the conservation of fruit pulps, the electrochemical behavior of the steel in an electrolyte which contained SO 2 and malic acid (which is the most abundant fruit acid in fruit pulp) was studied. It was shown that, in the presence of malic acid, at potentials close to the corrosion potential, the stainless steel is completely passive in 0.1 M Na 2SO 4 and, at potentials more positive than 0.7 V, two parallel processes occur: dissolution of the steel and anodic oxidation of malic acid into acetaldehyde. It was already observed that, in the presence of malic acid and sulfur dioxide, the anodic process of stainless steel dissolution is accelerated and has a pitting form. In the presence of SO 2, some acceleration of the cathodic process on stainless steel occurs as a consequence of SO 2 reduction. The obtained results indicate that the observed corrosion of process equipment made of stainless steel W.Nr. 1.4301 is caused mainly by the presence of SO 2 in the fruit pulp.

Corn steeping: influence of time and lactic acid on isolation and thermal properties of starch

A semi-dent corn hybrid was laboratory batch-steeped at 52°C in a sulfur dioxide solution (2500 ppm) and sulfur dioxide solution with lactic acid (2500 ppm SO 2+0.5% v/v lactic acid) for various time intervals. Starch was laboratory wet milled and gelatinization characteristics were analyzed by differential scanning calorimeter (DSC). Starch isolated from corn steeped in SO 2 solution alone had higher peak temperatures and narrower gelatinization range as the steeping time increased. This demonstrated that the wet milling process anneals corn starch during the isolation procedure. Such an effect was less pronounced when starch was milled from corn steeped with lactic acid. Higher starch yields were obtained from corn steeped in sulfur dioxide solution with lactic acid.