Sulfur dioxide clusters

Gas phase molecular aggregates that contain acid molecules have been produced with free jet expansion techniques and detected by using electron impact ionization mass spectrometry. The clusters of aqueous nitric acid paralleled many properties of the condensed phase. Multiple nitric acid molecules were found in the clusters that were sufficiently dilute. The acid molecule was absent in the ionized clusters involving HC1 and only water was evident. Experiments also demonstrated the reactivity of ammonia with aqueous nitric acid and sulfur dioxide clusters and of sulfur trioxide with water clusters. The natural occurrence of acid cluster negative ions offers a means to probe the gas phase acid loading of the atmosphere through laboratory and field studies of the ion chemistry. 

As previously mentioned, past studies used non-filtered air with unknown concentrations of trace gases at unknown relative humidities. Also, many of the studies used plastic aging chambers that may have introduced volatile monomers into the air. These unknown factors are important to determine in order to fully understand the nature of the ultrafine particle mode. According to the classical thermodynamic theory of ion cluster formation (Coghlan and Scott, 1983), the relative humidity and trace gases will affect the existence of condensation nuclei. Megaw and Wiffen (1961) observed an increase in nuclei formation with the presence of sulfur dioxide. 

Only three palladium clusters were reported. Sulfur dioxide reacts with Pd(CNBu )2 to form Pd3(SO2)2(CNBu )5 (310) of structure [705] (309), and reduc-... 

Stark, J. V., Park, D. G., Lagadic, I. and Klabunde, K. J. Nanoscale metal oxide particles/ clusters as chemical reagents. Unique surface chemistry on magnesium oxide as shown by enhanced adsorption of acid gases (sulfur dioxide and carbon dioxide) and pressure dependence, Chem. Mater., 1996, 8, 1904-1912. 

Stark JV, Park DG, Lagadic I, Klabunde KJ (1996) Nanoscale Metal Oxide Particles/Clusters as Chemical Reagents. Unique Surface Chemistry on Magnesium Oxide As Shown by Enhanced Adsorption of Acid Gases (Sulfur Dioxide and Carbon Dioxide) and Pressure Dependence, Chem Mater 8 1904-1912... 

With free jet expansion techniques, we have produced clusters of aqueous nitric acid (3 ), hydrochloric acid, sulfuric acid (4, pure acetic acid ( 5), and sulfur dioxide (6). For analogy to buffering, the formation of clusters containing ammonia have also been examined. These have included ammonia with aqueous nitric acid (7 ), hydrogen sulfide (7J), and sulfur dioxide (8). The basic experiment involves expansion of vapor through a nozzle, collima-tion of the jet with a skimmer to form a well-directed molecular beam, and detection of clusters via electron impact ionization and quadrupole mass spectrometry. Some variations include the introduction of a reactive gas into vacuum near the expansion as described elsewhere (4, 8) and the implementation of an electrostatic quadrupolar field to examine the polarity of the neutral clusters. The electric deflection technique is described by Klemperer and coworkers (9). 

When sulfur dioxide is introduced through the nozzle and the amount of ammonia behind the annular opening varies from 6 to 50 torr, the extent of ammonia incorporation into the clusters dramatically increases with increasing ammonia pressure. Up to two ammonia molecules were observed to be incorporated into the clusters with 20 torr of ammonia behind the annular opening. With 40 torr, up to four NH3 molecules were observed in the clusters. 

Model examples will be the study of the competitive clustering of ammonia and water on the ammonium ion and the determination of the characteristics of binding of water, carbon dioxide and sulfur dioxide on the nitrite ion, in relation to gas phase experimental measurements. 

Supported ruthenium carbido-cluster catalysts for the catalytic removal of nitrogen monoxide and sulfur dioxide the preparation process monitored by sulfur K-edge X-ray absorption near-edge structure... 

The preparation process of ruthenium carbido-cluster catalysts for the reduction of sulfur dioxide was traced by means of sulfur K-edge X-ray absorption near-edge structure (XANES). During the activation process, a pair of peaks at 2472.5 - 2472.8 and 2482.7 -2482.8 eV appeared. The pair was ascribed to the RuS phase. Once the catalysts were activated at 503 - 573 K, another pair of peaks at 2474.2 and 2479.2 eV appeared. The pair was assigned to the it and a transition peaks, respectively, of adsorbed SO molecules on the catalyst surface. 

Research on the long-term effects of low-level pollution continues. Air pollution by ozone, sulfur dioxide, and particulates in Britain kills 24,000 people annually.58 It is estimated that exposure to diesel exhaust over a 70-year lifetime will cause 450 cases of cancer per million people in California.59 Epidemiologists continue to investigate clusters of diseases such as the two to four times higher incidence of neural tube and certain heart defects in children born within A mile of Superfund sites in California,60 the lower birth weight and prematurity of infants born to... 

Other sets of N values were determined more directly from the rates of reaction between nucleophiles and tetramethylchloronium ions (20a) and the counterion was derived from antimony pentafluoride (20b) in sulfur dioxide solutions (20a) and of reaction between triethyloxonium fluorophosphate and nucleophiles used as solvents (21). The first approach (20a) has been criticized (21) on the ground that nucleophilicity of individual molecules or small clusters might be different from that of the compound as a solvent. The second approach (21) might be questioned for the assumption that solvent electrophilicity (18) has no effect on the measured rates. 

The tripalladium mixed-valence Pd3(2/3) and Pd3(4/3), Pd(II) and Pd(0) clusters may be formed with a range of phosphines, isocyanides, or carbonyls as terminal ligands and carbonyls, nitrosyls, isocyanides, sulfur dioxide, phosphides, phosphines or diphosphines, halides, thiolates as doubly or triply bridging ligands. These clusters exhibit a wide range of steric and electronic environments. 

C36H33lr70i2f Iridium heptanuclear cluster, 44B, 793 C36H4iIrP2, (Cycloocta-1,5-diene)(1,3-bis(diphenylphosphino)-propane)methyliridium(I), 39B, 648 C37H37FgMo02P3S, ((T -Cyclohexadiene) (T -cyclopentadiene) (1, 2-bis(di-phenylphosphino)ethane)molybdenum(V)) hexafluorophosphate sulfur dioxide, 43B, 1092... 

---