Photochemistry

Ruthenium-containing polymers derived from cis-dichloro-bis(2-2'-bipyridine) ruthenium and selected diamine-containing dyes have been synthesized. These polymeric products were characterized using FTIR, UV-Vis spectroscopy, light scattering photometry, and mass spectral analysis. Thermal degradation studies of these products are also presented.

The photodegradation of benzimidazole-based fungicides: benomyl ({1- [(butylamino) carbonyl)-1H-benzimidazol-2-yl} carbamic acid methyl ester), thiabendazole (2-(4-thiazolyl)-1H-benzimidazole) and fuberidazole (2-(2-furyl)-1H-benzimidazole) by ultraviolet radiation has been studied. Benomyl in an organic solvent (chloroform) undergoes a rapid degradation even without any UV radiation; UV radiation and air agitation will increase the rate of the reaction. The degradation product was found to be methyl 2-benzimidazolecarbamate (MBC) in all cases. The degradation of thiabendazole and fuberidazole in methanol was also studied under different conditions but degradation was observed only under UV radiation and in the presence of oxygen, 7-8 Photodegradation products were found in the mixture after irradiation of thiabendazole but only 2 of them were separated from the mixture and identified. Benzimidazole-2-carboxamide and dimethyl oxalate were two of the final photodegradation products of thiabendazole in methanol. It is clear that the thiazole ring is the most vulnerable part of the molecule and suffers ring cleavage. No photodegradation products of fuberidazole were identified so far.

OH vertical column abundances have been measured since 1977. Based on this long-term data base, the terrestrial OH abundance trends, such as the high-sun (secX = 1) enhancement of the zenith angle dependence, seasonal variations, and diurnal behaviors, have been observed. Current atmospheric models do not predict these features. In this thesis, a one dimensional photochemical model of the mesosphere has been constructed in order to examine the possibility that these observed effects might originate in this region of the atmosphere. Transport effects are not considered. The model result demonstrates that the observed OH behaviors are not caused by known photochemical reactions in the mesosphere.

Observations of the vertical column abundance of atmospheric
hydroxyl (OH) have been made using a Pepsios (polyetalon
pressure-scanned interferometric optical spectrometer). The
measurements were taken at both Fritz Peak, Colorado (40°N) and Boca
Raton, Florida (26° N) during the period 1985-86. These are high
resolution measurements of the resonance absorption of sunlight by OH in the P1(1) A^2 sigma - x^2 pi (0,0) transition at 3081.66 A. The observations are of relevance to the problem of stratospheric
ozone reduction by man-made pollution. Attempts to model the
photochemistry of the middle atmosphere and to predict its response to
these pollutants depend heavily on an accurate observational data base
of many middle atmospheric constituents. This OH data base contributes
information which is of critical importance to theories describing
middle atmospheric processes.
The author's measurements are discussed within the context of the
ten-year data base accumulated by Dr. Clyde Burnett. Observed
geographic and seasonal regularities, as well as short-period excursions
in the OH abundances, have not been fully explained by current
photochemical theory.

The photodegradation of propiconazole (1-{[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]methyl}-1 H-1,2,4-triazole), a systemic fungicide, by ultraviolet radiation has been studied. After 12 hours of continuous irradiation, propiconazole undergoes degradation in aqueous solution. The process requires the presence of oxygen and continuous agitation. Similarly, propiconazole undergoes degradation in organic solvents as well (methanol, hexane).