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Rearrangements, cyclizations, and co...

Skraba-Joiner, Sarah L.

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Rearrangements, cyclizations, and coupling reactions of polycyclic aromatic hydrocarbons.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Rearrangements, cyclizations, and coupling reactions of polycyclic aromatic hydrocarbons./
Author:	Skraba-Joiner, Sarah L.
Description:	192 p.
Notes:	Source: Dissertation Abstracts International, Volume: 77-03(E), Section: B.
Contained By:	Dissertation Abstracts International77-03B(E).
Subject:	Chemistry. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3727899
ISBN:	9781339131566

Rearrangements, cyclizations, and coupling reactions of polycyclic aromatic hydrocarbons.
Skraba-Joiner, Sarah L.

Rearrangements, cyclizations, and coupling reactions of polycyclic aromatic hydrocarbons. - 192 p.

Source: Dissertation Abstracts International, Volume: 77-03(E), Section: B.

Thesis (Ph.D.)--University of New Hampshire, 2015.

A series of rearrangements in polycyclic aromatic hydrocarbons were studied in a solution of trifluoromethane sulfonic acid (TfOH) in 1,2-dichloroethane (DCE). Ipso protonation of these arenes allows for 1,2-aryl group migration. In phenyl-substituted benzenes, meta-type products are generally formed as the major isomer at equilibrium. Potential energy surfaces for these rearrangements were calculated using density functional theory (DFT); major product formation is consistent with the formation of the lowest energy carbocation. Similar rearrangements were also observed in the binaphthyl system, which undergoes 1,2-naphthyl shifts in superacid media, forming 2,2'-binaphthyl as the major rearranged product. Prolonged heating in these cases results in Scholl cyclization. Skeletal rearrangements of acenes in similar reaction media have also been observed. From anthracene, phenanthrene is formed as the major product, along with reduced isomers. Mechanisms for isomerization were studied using DFT, in which protonation at a ring juncture allows for formation of a spirocyclic carbocation intermediate that can isomerize or automerize. In the case of anthracene/phenanthrene, the likely mechanism involves reduction, followed by isomerization, and finally re-oxidation. Similar rearrangements are observed in chrysene isomers; experiments and computational analysis suggest a direct isomerization mechanism. Acyl group migrations of aromatic ketones were also studied. 1-Acetonaphthone rearranged to 2-acetonaphthone upon heating in a TfOH/DCE solution. DFT analysis of the potential energy surface shows the formation of an intermediate pi-complex, bridging the 1- and 2- isomers. The major isomer formed is dictated by formation of the lowest energy carbocation. In these reactions, deacylation also occurs; the amount increases as the stability of the acylium ion formed increases. In addition to rearrangements, intermolecular Scholl coupling reactions of polycyclic aromatic hydrocarbons were studied. These reactions used TfOH with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as an added oxidant to synthesize rylenes and hexabenzocoronene derivatives from naphthalene and phenanthrene, respectively. While further work needs to be completed on the optimization of these syntheses and the purification of these compounds, these reactions show promise as a simple route to these materials.

ISBN: 9781339131566Subjects--Topical Terms:

516420
Chemistry.

Rearrangements, cyclizations, and coupling reactions of polycyclic aromatic hydrocarbons.
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245 1 0 $a Rearrangements, cyclizations, and coupling reactions of polycyclic aromatic hydrocarbons.
300 $a 192 p.
500 $a Source: Dissertation Abstracts International, Volume: 77-03(E), Section: B.
500 $a Adviser: Richard P. Johnson.
502 $a Thesis (Ph.D.)--University of New Hampshire, 2015.
520 $a A series of rearrangements in polycyclic aromatic hydrocarbons were studied in a solution of trifluoromethane sulfonic acid (TfOH) in 1,2-dichloroethane (DCE). Ipso protonation of these arenes allows for 1,2-aryl group migration. In phenyl-substituted benzenes, meta-type products are generally formed as the major isomer at equilibrium. Potential energy surfaces for these rearrangements were calculated using density functional theory (DFT); major product formation is consistent with the formation of the lowest energy carbocation. Similar rearrangements were also observed in the binaphthyl system, which undergoes 1,2-naphthyl shifts in superacid media, forming 2,2'-binaphthyl as the major rearranged product. Prolonged heating in these cases results in Scholl cyclization. Skeletal rearrangements of acenes in similar reaction media have also been observed. From anthracene, phenanthrene is formed as the major product, along with reduced isomers. Mechanisms for isomerization were studied using DFT, in which protonation at a ring juncture allows for formation of a spirocyclic carbocation intermediate that can isomerize or automerize. In the case of anthracene/phenanthrene, the likely mechanism involves reduction, followed by isomerization, and finally re-oxidation. Similar rearrangements are observed in chrysene isomers; experiments and computational analysis suggest a direct isomerization mechanism. Acyl group migrations of aromatic ketones were also studied. 1-Acetonaphthone rearranged to 2-acetonaphthone upon heating in a TfOH/DCE solution. DFT analysis of the potential energy surface shows the formation of an intermediate pi-complex, bridging the 1- and 2- isomers. The major isomer formed is dictated by formation of the lowest energy carbocation. In these reactions, deacylation also occurs; the amount increases as the stability of the acylium ion formed increases. In addition to rearrangements, intermolecular Scholl coupling reactions of polycyclic aromatic hydrocarbons were studied. These reactions used TfOH with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as an added oxidant to synthesize rylenes and hexabenzocoronene derivatives from naphthalene and phenanthrene, respectively. While further work needs to be completed on the optimization of these syntheses and the purification of these compounds, these reactions show promise as a simple route to these materials.
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650 4 $a Organic chemistry. $3 523952
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773 0 $t Dissertation Abstracts International $g 77-03B(E).
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