Photochemical formation of 9-chloroanthracene (MCA) from mixtures of 9,10-dichloroanthracene (DCA) and 2,5-dimethyl-2,4-hexadiene (DMH) in acetonitrile has been investigated using kinetic, deuterium labeling, and quenching techniques. Product studies are described which show that DCA is quantitatively converted to MCA when irradiated at 404 nm in degassed acetonitrile in the pressence of DMH. In the absence of DMH, DCA is photostable in acetonitrile. Photoformation of MCA in the DCA/DMH system is strongly inhibited by the presence of low concentrations of molecular oxygen or 1,2,4,5-tetracyanobenzene. Results from quenching studies, along with kinetic parameters given by the DMH concentration dependence of DCA disappearance and MCA appearance quantum yields implicate participation of the DCA-DMH singlet exciplex, DCA-2DMH singlet triplex, and DCA anion radical as intermediates in the photodechlorination reaction. Results from experiments employing deuterated DMH, deuterated acetonitrile, and acetonitrile containing D(,2)O or H(,2)O show that attachment of the 10-hydrogen of MCA occurs by (DCA) anion radical protonation, a finding which is discordant with free-radical mechanisms generally postulated for the quencher-induced photodehalogenation of haloaromatics. / The mechanism for the photocycloaddition of DCA to 1,3- cyclohexadiene (CHD) was investigated by spectroscopic and photochemical methods. Cycloadducts corresponding to {4(pi) + 4(pi)} addition of CHD across the 9,10- and 1,4-positions of DCA, and {2(pi) + 2(pi)} addition of CHD across DCA's 1,2-positions are the major products formed when DCA is irradiated in polar and nonpolar solvents in the presence of CHD. Chemical and physical evidence is presented which demonstrates that the DCA-CHD cycloadducts arise from chemical interactions in the singlet manifold, and indirect evidence is presented which suggestsinvolvement of a reversibly formed DCA-CHD singlet exciplex inthe photoaddition process. Findings which modify a previousdescription of photocycloaddition in the DCA/CHD system arereported. Investigation of the photophysical and photochemicalproperties of the 1,2-adduct and 9,10-adduct from the DCA/CHD / system has revealed an adiabatic photoreaction channel which converts adducts to CHD and singlet electronically-excited DCA. Quantum yields for adiabatic formation of ('1)DCA* from direct excitation of 1,2-adduct and 9,10-adduct in degassed acetonitrile (25.0(DEGREES)C) are / (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI) / respectively. Similar / (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI) / values are also obtained from 1,2- and 9,10-adduct in nonpolar solvents. / Source: Dissertation Abstracts International, Volume: 42-06, Section: B, page: 2382. / Thesis (Ph.D.)--The Florida State University, 1981.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_74574 |
| Contributors | SMOTHERS, WILLIAM KARL., Florida State University |
| Source Sets | Florida State University |
| Detected Language | English |
| Type | Text |
| Format | 380 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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