<p> Fluorosulphonic acid has been employed to generate
cyclohexadienyl cations by protonation of weak bases in
order to study the affect of uv light on such systems
which are variably substituted. Differing substitution
has been obtained by selecting polymethylbenzenes,
cyclohexadienones and polymethylphenols as cation precursors. </p> <p> The photoisomerization of the 1,2,4,5-te-tramethylcyclohexadienyl cation to the 1,2,4,5-tetramethylbicyclo-[3 .1.O.] hexenyl cation has been studied by nmr methods and is discussed mechanistically in terms of competitive electrocyclic and [ δ2a + π2a] mechanisms of ring closure. Investigations of a similar 1,2,3,5-tetrarnethylcyclohexadienyl cation failed to uncover an analogous photoisomerization. This result is briefly discussed in relation to the demonstrated instability of the supposed photo-product which has been produced by a non photo chemical route. </p> <p> Both the 1-hydroxy-6,6-dimethyl- and 1-hydroxy-4 1 4 dimethylcyclohexadienyl cations have been generated from the corresponding cyclohexadienones by low temperature protonation in FS03H. Photoisornerization of these systems produced the same 2-hydroxy-6,6-dimethylbicyclo[3.l.0.] hexenyl cation which underwent further photorearrangement to various protonated phenols, the nature
of which depended upon the frequency of irradiation. </p> <p> A number of protonated polymethylphenols have
been investigated with respect to their site(s) of
protonation in fluorosulphonic acid and their tendency
to undergo photochemical reaction. Several members of
this series have been shown to rearrange photochemically
to isomeric phenols through a bicyclo[3.l.O.] hexenyl
cation intermediate. A necessary criterion for this
reaction has been established as protonation of a methyl
bearing ring carbon. </p> <p> An exceptional example of the phenol photo-
isomerization was the photo-conversion of protonated
2,4,6-trimethy·lphenol·to protonated 1,3,5-trimethyl.
bicyclo[3.1.o] hex-3-en-2-one. This, as well as
additional evidence led to the conclusion that a significant amount of meta protonation occurred with
this phenol. </p> / Thesis / Master of Science (MSc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/19936 |
| Date | 11 1900 |
| Creators | Parrington, Barry |
| Contributors | Childs, R. F., Chemistry |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
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