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The photolysis in benzene of exo-5-benzoylbicyclo[2.1 .ljhexane (4) has been found to afford A2-cyclopentenylacetophenone (5) and 7-phenyltricyclo[3.2.0.02|6]heptan-7-ol (6). The formation of these products is considered to proceed through a diradical intermediate formed by transannular hydrogen abstraction by the excited n-ir* triplet state. The tricyclic alcohol was found to rearrange thermally to 4 and 5. The rearrangement to 4 was shown to proceed via cleavage of the bridgehead carbon-carbon bond followed by 1,5-H transfer. In basic media the tricyclic alcohol isomerized to ex:o-5-benzoylbicyclo[2.1.1 ]hexane with overall retention of configuration. The tricyclic alcohol was also found to be extremely unstable to acidic conditions and rearranged to 2-phenyl-anff-7-norbornenol. The rearrangement was rationalized as proceeding via a tricyclo[3.2.0.02'7]heptyl cation.

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The toxic effects of gas-phase singlet oxygen, 1O2, on the ciliated respiratory epithelium of hamster trachea have been demonstrated. Tracheal explants treated with 1O2 showed a dose-dependent decrease in cilia beating frequency and focal ciliostasis. A statistically significant decrease in ciliary activity occurred at 1O2 concentrations as low as 154 ppb after a 2-hr exposure. Cytological alterations in the mucociliary epithelium were observed in explants exposed to 235 ppb 1O2 or greater. When cytotoxic effects were related to the time of exposure to 1O2, maximum effects occurred after a 4-hr exposure. In vitro recovery studies indicate that ciliary activity returned to normal between 4 and 8 hr after exposure.