Photochemical chamber

Photochemical Chamber reactor fitted with RPR-3000 A lamps. The structures of the [6,6]-ring fused 1,2-dihydrofullerenes have been identified by standard spectroscopic methods. 

Alkene (36 mmol), fluorodiiodomethane (9.43 g, 33 mmol) (for the preparation see refs 1 and 5), CHjClj (175 mL) (or 1,1,2,2-tetrachloroethane in the case of low boiling products) and 5M NaOH (50 mL) were magnetically stirred in a Pyrex flask and irradiated with 3500-A lamps in a commercial Rayonet photochemical chamber for 24 h. After the separation of the organic layer and drying (MgS04), the solvent was removed by distillation and the monofluorocyclopropanes separated and purified by preparative GC (Carbowax 20 M or SE-30 columns). 

Experimental details.12 9 A solution of 457 (0.74 mmol) and triethylamine (2 mmol) in methanol was purged with nitrogen for 1 h and irradiated in a Rayonet photochemical chamber equipped with 16 low-pressure mercury discharge lamps (254nm) (Figure 3.10) for 12h. After irradiation, methanol was distilled off under reduced pressure and the product was purified by column chromatography in 90% chemical yield. 

Estimates of the average photolysis frequency of 2-hydroxyethanal on exposure to sunlight were made by Magneron et al. (2005) using the EUPHORE photochemical chamber during June 19-21, 1998, and June 15-16, 1999 mixtures of 2-hydroxyethanal with OH radical scavengers were exposed in air for periods of 5-7 h. The mean /-value for photodecomposition by all pathways was reported as (1.1 0.3) X 10- s-i. 

Table 2-6 is a list of some compounds that may be present in photochemical smog, but have not yet been reported. The presence of some of these compounds (such as PBzN and ketene) seems very probable, in diat they have been observed in smog-chamber studies, whereas others are... 

McAfee, J. M., J. N. Pitts. Jr., and A. M. Winer. In-situ Long-path Infrared Spectroscopy of Photochemical Air Pollutants in an Environmental Chamber. Paper No. 125 Presented at the Pacific Conference on Chemistry and Spectroscopy, San Francisco, California, October 16-18, 1974. (American Chemical Society—lOth Western Regional Meeting and Society for Applied Spectroscopy—13th Pacific Meeting)... 

The diurnal patterns of ozone, nitric oxide, and nitrogen dioxide concentrations observed during photochemical oxidant episodes in California have been confirmed by smog-chamber studies. There may be, however, a decrease in reliability with decreasing concentration of values less than 0.1 ppm that were measured by the colorimetric method. The magnitude of these uncertainties among the various monitoring networks in the United States has still to be assessed. 

A study in field chambers with ambient photochemical-oxidant (ozone) concentrations. 

Chloroplasts. Intact chloroplasts were isolated from freshly harvested growth chamber-grown spinach (Splnacla oleracea L.) as described by Lilley and Walker (10). Thylakoids were prepared by the method of Armond t al. (11). Chlorophyll concentrations were determined by the method of MacKinney (12). Photochemical reactions yere conducted at 25°C with a photon fluence rate of 750... 

Smog chamber studies have documented similar aerosol growth mechanisms. For example, in the photochemical oxidation of dimethyl sulfide, the formation and growth of particles in an initially particle-free system was observed. However, if seed particles with 34-nm mean size were present, an oscillation in the... 

Flagan, R. C., S.-C. Wang, F. Yin, J. H. Seinfeld, G. Reischi, W. Winklniayr, and R. Karch, Electrical Mobility Measurements of Fine-Particle Formation during Chamber Studies of Atmospheric Photochemical Reactions, Environ. Sci. Technol., 25, 883-890 (1991). 

The results from such chamber studies are frequently used to test the chemical portion of various computer models for photochemical air pollution in order to provide a scientific basis for control strategies. While the interpretation of the results of smog chamber studies and their extrapolation to atmospheric conditions also have some limitations (vide infra), such studies do provide a highly useful means of initially examining the emissions-air quality relationship under controlled conditions. 

Clearly, environmental chamber studies are very useful tools in examining the chemical relationships between emissions and air quality and for carrying out related (e.g., exposure) studies. Use of these chambers has permitted the systematic variation of individual parameters under controlled conditions, unlike ambient air studies, where the continuous injection of pollutants and the effects of meteorology are often difficult to assess and to quantitatively incorporate into the data analysis. Chamber studies have also provided the basis for the validation of computer kinetic models. Finally, they have provided important kinetic and mechanistic information on some of the individual reactions occurring during photochemical smog formation. 

However, despite these complications, smog chambers have proven extremely useful in studying the chemistiy of photochemical air pollution under controlled conditions in which emissions and meteorology are not complicating factors. While there are some... 

Akimoto, H., M. Hoshino, G. Inoue, F. Sakamaki, N. Washida, and M. Okuda, Design and Characterization of the Evacuable and Bakable Photochemical Smog Chamber, Environ. Sci. Technol., 13, 471-475 (1979). 

Behnke, W., W. Hollander, W. Koch, F. Nolting, and C. Zetzsch, A Smog Chamber for Studies of the Photochemical Degradation of Chemicals in the Presence of Aerosols, Atmos. Environ., 22, 1113-1120 (1988). 

Dodge, M. C., Combined Use of Modeling Techniques and Smog Chamber Data to Derive Ozone-Precursor Relationships, in Proceedings of the International Conference on Photochemical Oxidant Pollution and Its Control (B. Dimitriades, Ed.), EPA-600/3-77-001b, Vol. II, pp. 881-889, 1977a. 

Evans, L. F I. A. Weeks, and A. J. Eccleston, A Chamber Study of Photochemical Smog in Melbourne, Australia—Present and Future, Atmos. Environ., 20, 1355-1368(1986). 

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