Date of Award

3-1-1994

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Abstract

Radical anions of 9-phenoxyanthracene (1) and 9-phenoxyphenanthrene (2) were generated on platinum in dimethylformamide/tetra-n-butylammonium perchlorate at $-$1.84 V vs. SCE and $-$2.37 V, respectively. Dianions of 1 and 2 were produced at $-$2.58 V and $-$2.95 V, respectively. Chronoamperometric techniques demonstrated that radical anions of 1 and 2 have their half-lifes greater than 1000 seconds and 200 seconds, respectively. The radical anions of 1 and 2 underwent an unimolecular bond scission at the aryl carbon-oxygen bond to generate aryl radicals and phenoxide ions. The cleavage reaction for the radical anion of 1 at the anthryl carbon-oxygen bond was found to be consistent with a regioconservation-of-spin model. The reaction pathways for dianions of 1 and 2 were most consistent with a protonation-elimination reaction, which generate the aromatic hydrocarbons and phenoxide ions. The half-life for the dianion of 1 was determined to be approximately 3 ms with cyclic voltammetric and chronoamperometric measurements. 9-Methoxyanthracene (3) and 9-methoxy-phenanthrene (4) were reduced to their respective radical anions on platinum at potentials of $-$1.93 V vs. SCE and $-$2.54 V, respectively. The half-lifes of the radical anions of 3 and 4 were determined to be greater than 100 seconds and one second, respectively. The radical anions of 3 and 4 underwent an unimolecular bond cleavage at the methyl carbon-oxygen bond to generate methyl radicals and aryloxide ions. The cleavage reaction for the radical anion of 3 at the methyl carbon-oxygen bond was found to be consistent with a regioconservation-of-spin model. The dianion of 3 was generated on platinum at a potential of $-$2.63 V vs. SCE. The dianion of 3 underwent a protonation-elimination reaction pathway to produce anthracene and methoxide ion. 1-Bromo-2-(3$\sp\prime$-butenyl)-naphthalene (5) was reduced by direct electrochemical reduction techniques on platinum at $-$2.18 V vs. SCE in dimethylformamide/tetra-n-butylammonium perchlorate. The reduction pathway in the direct electrochemical reduction of 5 followed an ECE mechanism. An EC mechanism was postulated as the pathway in the indirect electrochemical reduction of 5 at $-$1.95 V vs. SCE using aromatic compounds as electron-transfer mediators. Cyclization of a 2-(3$\sp\prime$-butenyl)naphthyl radical, which resulted from carbon-bromide bond scission of 5, produced 1-methylbenz (e) indan. The 2-(3$\sp\prime$-butenyl) substituent proved to be an effective probe for the aryl radicals in the bond scission reactions that result from direct and indirect electrochemical reduction of organic substrates.

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