{"id":{"repo_id":"vt","oai_identifier":"oai:vtechworks.lib.vt.edu:10919/54185"},"canonical_url":"https://search.dev.ndltd.org/etd/vt/oai:vtechworks.lib.vt.edu:10919/54185","repository":{"repo_id":"vt","name":"Virginia Tech","base_url":"https://vtechworks.lib.vt.edu/oai/request"},"display":{"title":"Stereoelectronic effects in brominations of cyclopropylarenes and 9-alkylanthracenes","abstract":"The free radical bromination of several cyclopropylarenes has been studied. The abstraction of a cyclopropyl hydrogen by bromine atom, which to date has been an unrecognized process, is demonstrated in this study. Specifically, when a cyclopropyl group is attached to the 9-position of an anthracene, an unprecedented hydrogen abstraction product, the corresponding cyclopropyl bromide, is obtained. This is believed to be due to stereoelectronic effects. Molecular mechanics calculations and X-ray crystallography have been used to demonstrate that 9-cycIopropylanthracene, unlike other cyclopropylarenes, is effectively locked in a conformation which places the a-cyclopropyl C-H bond in alignment with the p-orbitals of the aromatic system. This proper alignment activates the a-cyclopropyl hydrogen for abstraction by bromine atom. The relative reactivities of several 9-alkylanthracenes towards bromine atom are established, namely: 9-methyI- > 9-cyclopropyI- > 9-ethyl- >> 9-isopropylanthracene. Semi-empirical molecular orbital theory and molecular mechanics calculations have been utilized to demonstrate that the relative reactivities are not a function of bond dissociation energies but rather a function of the size of the dihedral angle between the a C-H bonds and the plane of the central ring of the various 9-alkylanthracenes in their lowest energy conformations. The absolute rate constants for the abstraction of hydrogen by bromine atom from 9-methyl-, 9-cyclopropyl-, and 9·ethylanthracene are estimated to be 1.1 x 10⁸ M⁻¹ sec⁻¹, 3.8 x 10⁷ M⁻¹ sec⁻¹ and 7.2 x 10⁶ M⁻¹ sec⁻¹ respectively. The value for the primary hydrogen/deuterium isotope effect for the abstraction of hydrogen by bromine atom from 9-cyclopropylanthracene is determined to be 2.6. All of the above observations lend support to the importance of stereoelectronic effects in the free radical bromination of the cyclopropylarenes and 9-alkylanthracenes.","abstract_html":"The free radical bromination of several cyclopropylarenes has been studied. The abstraction of a cyclopropyl hydrogen by bromine atom, which to date has been an unrecognized process, is demonstrated in this study. Specifically, when a cyclopropyl group is attached to the 9-position of an anthracene, an unprecedented hydrogen abstraction product, the corresponding cyclopropyl bromide, is obtained. This is believed to be due to stereoelectronic effects. Molecular mechanics calculations and X-ray crystallography have been used to demonstrate that 9-cycIopropylanthracene, unlike other cyclopropylarenes, is effectively locked in a conformation which places the a-cyclopropyl C-H bond in alignment with the p-orbitals of the aromatic system. This proper alignment activates the a-cyclopropyl hydrogen for abstraction by bromine atom. The relative reactivities of several 9-alkylanthracenes towards bromine atom are established, namely: 9-methyI- > 9-cyclopropyI- > 9-ethyl- >> 9-isopropylanthracene. Semi-empirical molecular orbital theory and molecular mechanics calculations have been utilized to demonstrate that the relative reactivities are not a function of bond dissociation energies but rather a function of the size of the dihedral angle between the a C-H bonds and the plane of the central ring of the various 9-alkylanthracenes in their lowest energy conformations. The absolute rate constants for the abstraction of hydrogen by bromine atom from 9-methyl-, 9-cyclopropyl-, and 9·ethylanthracene are estimated to be 1.1 x 10⁸ M⁻¹ sec⁻¹, 3.8 x 10⁷ M⁻¹ sec⁻¹ and 7.2 x 10⁶ M⁻¹ sec⁻¹ respectively. The value for the primary hydrogen/deuterium isotope effect for the abstraction of hydrogen by bromine atom from 9-cyclopropylanthracene is determined to be 2.6. All of the above observations lend support to the importance of stereoelectronic effects in the free radical bromination of the cyclopropylarenes and 9-alkylanthracenes.","abstract_has_math":false,"creators":["Hakim, Mas Rosemal"],"institution":"Virginia Polytechnic Institute and State University","degree_name":"Ph. D.","degree_level":"doctoral","degree_discipline":"Chemistry","degree_department":"Chemistry","school":null,"contributors":[],"advisors":[],"committee_chairs":["Tanko, James M."],"committee_members":["McGrath, James E.","Gibson, Harry W.","Taylor, Larry T.","Dorn, Harry C."],"year":1989,"date_issued":"1989","date_published":"1989","updated_at":"2026-07-22T22:19:26Z","subjects":[],"languages":["en_US"],"rights":["In Copyright"],"rights_urls":["http://rightsstatements.org/vocab/InC/1.0/"],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/10919/54185","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.committeechair","label":"Committee Chair","values":["Tanko, James M."]},{"key":"dc:contributor.committeemember","label":"Committee Member","values":["McGrath, James E.","Gibson, Harry W.","Taylor, Larry T.","Dorn, Harry C."]},{"key":"dc:contributor.department","label":"Department","values":["Chemistry"]},{"key":"dc:creator","label":"Author","values":["Hakim, Mas Rosemal"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2015-07-09T20:43:13Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2015-07-09T20:43:13Z"]},{"key":"dc:date.issued","label":"Date","values":["1989"]},{"key":"dc:publisher","label":"Institution","values":["Virginia Polytechnic Institute and State University"]},{"key":"dc:type","label":"Dc Type","values":["Dissertation"]},{"key":"dc:type.dcmitype","label":"Dc Type Dcmitype","values":["Text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Chemistry"]},{"key":"thesis:degree_level","label":"Degree Level","values":["doctoral"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph. D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Virginia Polytechnic Institute and State University"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en_US"]},{"key":"dc:rights","label":"Dc Rights","values":["In Copyright"]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://rightsstatements.org/vocab/InC/1.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/10919/54185"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The free radical bromination of several cyclopropylarenes has been studied. The abstraction of a cyclopropyl hydrogen by bromine atom, which to date has been an unrecognized process, is demonstrated in this study. Specifically, when a cyclopropyl group is attached to the 9-position of an anthracene, an unprecedented hydrogen abstraction product, the corresponding cyclopropyl bromide, is obtained. This is believed to be due to stereoelectronic effects. Molecular mechanics calculations and X-ray crystallography have been used to demonstrate that 9-cycIopropylanthracene, unlike other cyclopropylarenes, is effectively locked in a conformation which places the a-cyclopropyl C-H bond in alignment with the p-orbitals of the aromatic system. This proper alignment activates the a-cyclopropyl hydrogen for abstraction by bromine atom. The relative reactivities of several 9-alkylanthracenes towards bromine atom are established, namely: 9-methyI- > 9-cyclopropyI- > 9-ethyl- >> 9-isopropylanthracene. Semi-empirical molecular orbital theory and molecular mechanics calculations have been utilized to demonstrate that the relative reactivities are not a function of bond dissociation energies but rather a function of the size of the dihedral angle between the a C-H bonds and the plane of the central ring of the various 9-alkylanthracenes in their lowest energy conformations. The absolute rate constants for the abstraction of hydrogen by bromine atom from 9-methyl-, 9-cyclopropyl-, and 9·ethylanthracene are estimated to be 1.1 x 10⁸ M⁻¹ sec⁻¹, 3.8 x 10⁷ M⁻¹ sec⁻¹ and 7.2 x 10⁶ M⁻¹ sec⁻¹ respectively. The value for the primary hydrogen/deuterium isotope effect for the abstraction of hydrogen by bromine atom from 9-cyclopropylanthracene is determined to be 2.6. All of the above observations lend support to the importance of stereoelectronic effects in the free radical bromination of the cyclopropylarenes and 9-alkylanthracenes."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Ph. D."]},{"key":"dc:format.mimetype","label":"Dc Format Mimetype","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Stereoelectronic effects in brominations of cyclopropylarenes and 9-alkylanthracenes"]}]}],"canonical_facts":{"dc:contributor.committeechair":["Tanko, James M."],"dc:contributor.committeemember":["McGrath, James E.","Gibson, Harry W.","Taylor, Larry T.","Dorn, Harry C."],"dc:contributor.department":["Chemistry"],"dc:creator":["Hakim, Mas Rosemal"],"dc:date.accessioned":["2015-07-09T20:43:13Z"],"dc:date.available":["2015-07-09T20:43:13Z"],"dc:date.issued":["1989"],"dc:description.abstract":["The free radical bromination of several cyclopropylarenes has been studied. The abstraction of a cyclopropyl hydrogen by bromine atom, which to date has been an unrecognized process, is demonstrated in this study. Specifically, when a cyclopropyl group is attached to the 9-position of an anthracene, an unprecedented hydrogen abstraction product, the corresponding cyclopropyl bromide, is obtained. This is believed to be due to stereoelectronic effects. Molecular mechanics calculations and X-ray crystallography have been used to demonstrate that 9-cycIopropylanthracene, unlike other cyclopropylarenes, is effectively locked in a conformation which places the a-cyclopropyl C-H bond in alignment with the p-orbitals of the aromatic system. This proper alignment activates the a-cyclopropyl hydrogen for abstraction by bromine atom. The relative reactivities of several 9-alkylanthracenes towards bromine atom are established, namely: 9-methyI- > 9-cyclopropyI- > 9-ethyl- >> 9-isopropylanthracene. Semi-empirical molecular orbital theory and molecular mechanics calculations have been utilized to demonstrate that the relative reactivities are not a function of bond dissociation energies but rather a function of the size of the dihedral angle between the a C-H bonds and the plane of the central ring of the various 9-alkylanthracenes in their lowest energy conformations. The absolute rate constants for the abstraction of hydrogen by bromine atom from 9-methyl-, 9-cyclopropyl-, and 9·ethylanthracene are estimated to be 1.1 x 10⁸ M⁻¹ sec⁻¹, 3.8 x 10⁷ M⁻¹ sec⁻¹ and 7.2 x 10⁶ M⁻¹ sec⁻¹ respectively. The value for the primary hydrogen/deuterium isotope effect for the abstraction of hydrogen by bromine atom from 9-cyclopropylanthracene is determined to be 2.6. All of the above observations lend support to the importance of stereoelectronic effects in the free radical bromination of the cyclopropylarenes and 9-alkylanthracenes."],"dc:description.degree":["Ph. D."],"dc:format.mimetype":["application/pdf"],"dc:identifier.uri":["http://hdl.handle.net/10919/54185"],"dc:language.iso":["en_US"],"dc:publisher":["Virginia Polytechnic Institute and State University"],"dc:rights":["In Copyright"],"dc:rights.uri":["http://rightsstatements.org/vocab/InC/1.0/"],"dc:title":["Stereoelectronic effects in brominations of cyclopropylarenes and 9-alkylanthracenes"],"dc:type":["Dissertation"],"dc:type.dcmitype":["Text"],"thesis:degree_discipline":["Chemistry"],"thesis:degree_level":["doctoral"],"thesis:degree_name":["Ph. D."],"thesis:institution_name":["Virginia Polytechnic Institute and State University"]},"updated_at":"2026-07-22T22:19:26Z"}