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Photochemistry of some naphthoquinols in solid polymer matrices

University of British Columbia

The main objective of this work was to study how polymer media can modify the photochemical reactivity of dissolved guest molecules. Three tetrahydronaphthoquinols, whose photochemistry is known to be sensitive to the reaction medium, were synthesized for this study. The photochemistry of these compounds consisted of [2 + 2] cycloaddition in solution and hydrogen abstraction-initiated rearrangement in the solid state. Different photopro-ducts from solution and solid state photolysis were interpreted as being due to reaction from different conformers in the different media. 2,3,4aα,6,7,8aα-hexamethyl-4a,5,8,8a-tetrahydronaphthoquin- l-on-4β-ol, studied in poly(methyl methacrylate) and poly(vinyl acetate) films, was found to exhibit behavior that is intermediate to solution and solid state reactivity and is discontinuous at the glass transition temperature. 2,3,4aα,6,7,8aα-hexamethyl-4a,5,8,8a-tetrahydronaphthoquin-l-on-4α-ol, which was essentially unreactive in the solid state, was also studied. It was found to give the expected but not observed solid state product as the major product in poly(methyl methacrylate). Finally, 2 , 3 ,4aα ,6,7, 8aα:-4a ,5,8, 8a- tetrahydronaphthoquin-1-on-4β-acetate was studied. As a result of differences in the local enviroment, this compound displayed unique photoreactivity in each of three different media: in solution it gave 5-exo-acetoxy-l,3,4,6,8,9-hexamethyltetracyclo [4.4.0.0[sup 3,9].0[sup 4,8]decan-2-one, in the pure crystalline phase it gave 5-exo-acetoxy-2-oxy-1,3,4,6,8,9-hexamethyltricyclo[4.4.0.0[sup 4,7]-dec-8-en -2-one and in poly(methyl methacrylate) films 5-exo-acetoxy-1,3,4,6,8,9-hexamethyltetracyclo[4.4.0.0[sup 3,7]dec-8-en-2-one, as a major product. It has been demonstrated that polymer matrices are useful reaction media for reducing the rates of conformational interconversions to the point that alternative chemical processes that are normally too slow to be observed in solution become competitive. This leads to chemical consequences that in some cases mimic those observed in the solid state. In others, where crystals are unreactive for some reasons or where the crystal lattice can sterically impede certain reactions, new products can be formed.

Text

2010-08-16

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http://hdl.handle.net/2429/27471

Chemistry

University of British Columbia

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