<p> A detailed study of the photoaddition of 3-phenylcyclohex-
2-enone and 2,3-dimethylbut-2-ene was undertaken
in order to gain mechanistic information of the photochemistry
of this enone. Photoadditions of this enone with
cyclopentene, norbornene, and but-2-ene were also studied.
Sensitization experiments showed that photoaddition with
2,3-dimethylbut-2-ene occurs when triplet sensitizers such
as Michler's ketone or 2-acetonaphthone are used. The
sensitized reactions are less efficient than the direct
irradiation, except at infinite 2,3-dimethylbut-2-ene concentration,
when the quantum yields for direct and sensitized
processes are the same. This quantitative result may be
explained by (a) inefficiency in the energy-transfer process from the sensitizer to enone 0 or (b) two excited states of
enone being involved in the direct and sensitized processeso
There are evidences that the excited state involved in the
direct irradiation could possibly be the second triplet of
the enoneo The presence of a higher enone tTiplet (T2)
was established by the observed dimerization of norbornene.
Cis-trans isomerization of but-2-ene was observed during
photoaddition, which could also be attributed to a higher
triplet, or to a 1,4-diradical intermediates Quenching
studies provided an estimate of the lifetime of the reactive
excited state in the direct irradiation. The energies
of the electronic states of the enone were estimated from
spectroscopic and chemical measurements. The formation of
an enoneoolefin 1,4-diradical has been proposed to explain
the effect of olefin concentration on the photoaddition. </p> / Thesis / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/20040 |
| Date | 06 1900 |
| Creators | Ramachandran, Bellampalli |
| Contributors | McCullough, John, Chemistry |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
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