Date of Award

Winter 2016

Project Type

Thesis

Program or Major

Chemistry

Degree Name

Master of Science

First Advisor

Richard P Johnson

Second Advisor

Glen P Miller

Third Advisor

Sterling A Tomellini

Abstract

Various synthetic routes towards polycyclic aromatic hydrocarbons dibenzo[g,p]chrysene (DBC), chrysene, zethrene, and their derivatives were studied. All of these compounds are not readily available and the literature lacks facile, efficient, and scalable syntheses. Microwave flash pyrolysis (MFP) was used for the synthesis of benzyne and phenanthryne, both of which have the ability to undergo a Diels-Alder reaction at the bay region of polycyclic aromatic hydrocarbons. Phthalic anhydride was used as a benzyne precursor and 9,10-dicarboxyphenanthrene anhydride as a phenanthryne precursor. DBC was observed after the MFP of biphenyl and 9,10-dicarboxyphenanthrene anhydride, signifying phenanthryne generation. Fluoride-induced elimination and Grignard pathways were also explored for phenanthryne formation, but no indication of phenanthryne was seen. DBC was efficiently prepared via a synthetic sequence that is the functional equivalent of the Stone-Wales rearrangement. This sequence is referred to as the pinacol-pinacolone Stone-Wales sequence, which provides DBC in high yield under mild reaction conditions. This is one of the most efficient and scalable syntheses of DBC with all of the steps providing high yields in short reaction times. Calculations for the rearrangement steps using density functional theory (DFT) further support the conclusion of a very efficient synthetic pathway. The same conditions were not successful for the synthesis of chrysene, however treatment of 1-indanopinacol with polyphosphoric acid (PPA) did provide chrysene, suggesting an alternative mechanism from the pinacol-pinacolone Stone-Wales route. For the synthesis of zethrene, the pinacol-pinacolone Stone-Wales sequence was applied to 1-acenaphthenopinacol, but like 1-indanopinacol, no pinacolone structure was observed. Treatment of 1-acenaphthenopinacol with PPA in a microwave reactor generated a small amount of zethrene. This suggests that the reaction between aromatic pinacols and PPA is an alternative and simple route towards polycyclic aromatic hydrocarbons. Other pathways for zethrene synthesis were also studied. Although further work needs to be completed to optimize the syntheses of chrysene and zethrene, these reactions show promise as mild, simple pathways towards these compounds.

Additional Files
Caitlin_Hoffman_MastersthesisNMRsupplemental.pdf (641 kB)
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