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Published on: April 22, 2016
Photochemical dimerization of acephenanthrylene and the heavy atom effect
1Department of Chemistry, Trinity University, San Antonio, Texas 78212-7200, USA.
The Journal of Organic Chemistry
|May 18, 2000
Summary
Photodimerization of acephenanthrylene forms cis and trans dimers, influenced by solvent and oxygen. Trans dimers cleave faster than cis dimers upon irradiation.
Area of Science:
- Photochemistry
- Organic Chemistry
- Physical Chemistry
Background:
- Acephenanthrylene undergoes photodimerization upon irradiation with visible light.
- The reaction produces both cis and trans stereoisomers.
- Solvent polarity and the presence of oxygen significantly influence the reaction outcome.
Purpose of the Study:
- To investigate the solution-phase photodimerization of acephenanthrylene.
- To determine the effect of solvent and oxygen on the formation of cis and trans photodimers.
- To study the photolytic cleavage of the formed dimers.
Main Methods:
- Irradiation of acephenanthrylene in various solvents (cyclohexane, chloroform, dibromomethane, ethyl iodide) using visible light (419 nm).
- Analysis of cis/trans dimer ratios under different conditions, including the presence and absence of oxygen.
- Photolytic cleavage studies of isolated cis and trans dimers using UV light (254 nm).
Main Results:
- Photodimerization yields cis and trans acephenanthrylene dimers, with ratios dependent on solvent and oxygen presence.
- A significant heavy atom effect was observed, influencing photodimerization rates.
- Dissolved oxygen selectively quenches the reaction, exclusively forming cis stereoisomers.
- Trans dimers exhibit faster photolytic cleavage rates compared to cis dimers upon 254 nm irradiation.
Conclusions:
- Solvent and oxygen play critical roles in controlling the stereoselectivity of acephenanthrylene photodimerization.
- The heavy atom effect and oxygen quenching are key factors in this photochemical process.
- Differential photolytic stability of cis and trans dimers is attributed to excited state stabilization in cis isomers.
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