{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/70201"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/70201","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Stereoisomerization of Hexacoordinate Sulfur and Tellurium","abstract":"The reaction of bromine trifluoride with sulfurane 1 gives rise to the first reported isolation of geometrical isomers of 12-S-6 sulfur, the trans- and cis-persulfuranes 2 and 3. The cis isomer is 2.0 (+OR-) 0.1 kcal/mol more favored in free energy than the all trans isomer in methylene chloride solution at 25(DEGREES)C. Calorimetry showed the trans-to-cis isomerization to be exothermic by 1.6 (+OR-) 0.5 kcal/mol. The rapid, acid-catalyzed isomerization of trans isomer 2 to give cis isomer 3 occurs by a dissociative mechanism through a pentacoordinate cationic sulfur intermediate, a 10-S-5 persulfonium ion, which was isolated as its hexafluorophosphate salt. A lower limit for the activation barrier of the unobserved nondissociative isomerization of 2 to 3 is 50 kcal/mol in quinoline solution. Polarization and other effects on the relative bond lengths and energies of the isomers are discussed. The results of complete X-ray structure determinations for 2 and 3 are described together with a PMO argument rationalizing the observed order of bond lengths.","abstract_html":"The reaction of bromine trifluoride with sulfurane 1 gives rise to the first reported isolation of geometrical isomers of 12-S-6 sulfur, the trans- and cis-persulfuranes 2 and 3. The cis isomer is 2.0 (+OR-) 0.1 kcal/mol more favored in free energy than the all trans isomer in methylene chloride solution at 25(DEGREES)C. Calorimetry showed the trans-to-cis isomerization to be exothermic by 1.6 (+OR-) 0.5 kcal/mol. The rapid, acid-catalyzed isomerization of trans isomer 2 to give cis isomer 3 occurs by a dissociative mechanism through a pentacoordinate cationic sulfur intermediate, a 10-S-5 persulfonium ion, which was isolated as its hexafluorophosphate salt. A lower limit for the activation barrier of the unobserved nondissociative isomerization of 2 to 3 is 50 kcal/mol in quinoline solution. Polarization and other effects on the relative bond lengths and energies of the isomers are discussed. The results of complete X-ray structure determinations for 2 and 3 are described together with a PMO argument rationalizing the observed order of bond lengths.","abstract_has_math":false,"creators":["Michalak, Ronald Stanley"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Chemistry","degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2014,"date_issued":"2014-12-15T23:17:47Z","date_published":"2014-12-15T23:17:47Z","updated_at":"2026-07-22T22:26:02Z","subjects":["Chemistry, Organic"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["(UMI)AAI8302936"],"render_values":[{"text":"(UMI)AAI8302936","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/70201","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Michalak, Ronald Stanley"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2014-12-15T23:17:47Z","10000-01-01","1982"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Chemistry"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Chemistry, Organic"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/70201","(UMI)AAI8302936"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["The reaction of bromine trifluoride with sulfurane 1 gives rise to the first reported isolation of geometrical isomers of 12-S-6 sulfur, the trans- and cis-persulfuranes 2 and 3. The cis isomer is 2.0 (+OR-) 0.1 kcal/mol more favored in free energy than the all trans isomer in methylene chloride solution at 25(DEGREES)C. Calorimetry showed the trans-to-cis isomerization to be exothermic by 1.6 (+OR-) 0.5 kcal/mol. The rapid, acid-catalyzed isomerization of trans isomer 2 to give cis isomer 3 occurs by a dissociative mechanism through a pentacoordinate cationic sulfur intermediate, a 10-S-5 persulfonium ion, which was isolated as its hexafluorophosphate salt. A lower limit for the activation barrier of the unobserved nondissociative isomerization of 2 to 3 is 50 kcal/mol in quinoline solution. Polarization and other effects on the relative bond lengths and energies of the isomers are discussed. The results of complete X-ray structure determinations for 2 and 3 are described together with a PMO argument rationalizing the observed order of bond lengths.","The reactions of bromine trifluoride with telluranes 9 and 10 give rise to the all-trans 12-Te-6 species, pertelluranes 3 and 13. The rate of isomerization from the all-trans geometry of 3 to the more stable isomer 4 with cis fluorines and oxygens and trans carbons was determined in different solvents and at different concentrations at 61(DEGREES)C. Failure to trap fluoride ion by added hexamethyldisilazane provides evidence against a dissociative mechanism involving Te-F bond heterolysis to give dissociated ions. The similarity of first-order rates of reaction {2.0 x 10('-5) to 2.5 x 10('-5) sec('-1) at 61(DEGREES)C} in solvents of differing ionizing power (Z-values in the range 54 to 64.2) provides evidence against any heterolytic dissociation mechanism for the isomerization of 3 to 4. The most probable mechanism for the permutational isomerization is concluded to be a nondissociative twist mechanism involving no cleavage of any of the six bonds to tellurium. The isomerization of 13 to a stereoisomer was not observed, either thermally or in the presence of Lewis acids. This could result from a higher activation barrier for the isomerization, or 13 could represent the most thermodynamically stable isomer in the set of possible stereoisomers. The results of complete X-ray crystallographic structure determinations of pertellurane 4 and tellurane 5 are described.","Made available in DSpace on 2014-12-15T23:17:47Z (GMT). No. of bitstreams: 1 8302936.pdf: 4004795 bytes, checksum: c563ee05a959f05eb53e6f07fa8d513e (MD5) Previous issue date: 1982","Embargo set by: Seth Robbins for item 70367 Lift date: Forever Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","U of I Only","138 p.","Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1982."]},{"key":"dc:title","label":"Title","values":["Stereoisomerization of Hexacoordinate Sulfur and Tellurium"]}]}],"canonical_facts":{"dc:creator":["Michalak, Ronald Stanley"],"dc:date":["2014-12-15T23:17:47Z","10000-01-01","1982"],"dc:description":["The reaction of bromine trifluoride with sulfurane 1 gives rise to the first reported isolation of geometrical isomers of 12-S-6 sulfur, the trans- and cis-persulfuranes 2 and 3. The cis isomer is 2.0 (+OR-) 0.1 kcal/mol more favored in free energy than the all trans isomer in methylene chloride solution at 25(DEGREES)C. Calorimetry showed the trans-to-cis isomerization to be exothermic by 1.6 (+OR-) 0.5 kcal/mol. The rapid, acid-catalyzed isomerization of trans isomer 2 to give cis isomer 3 occurs by a dissociative mechanism through a pentacoordinate cationic sulfur intermediate, a 10-S-5 persulfonium ion, which was isolated as its hexafluorophosphate salt. A lower limit for the activation barrier of the unobserved nondissociative isomerization of 2 to 3 is 50 kcal/mol in quinoline solution. Polarization and other effects on the relative bond lengths and energies of the isomers are discussed. The results of complete X-ray structure determinations for 2 and 3 are described together with a PMO argument rationalizing the observed order of bond lengths.","The reactions of bromine trifluoride with telluranes 9 and 10 give rise to the all-trans 12-Te-6 species, pertelluranes 3 and 13. The rate of isomerization from the all-trans geometry of 3 to the more stable isomer 4 with cis fluorines and oxygens and trans carbons was determined in different solvents and at different concentrations at 61(DEGREES)C. Failure to trap fluoride ion by added hexamethyldisilazane provides evidence against a dissociative mechanism involving Te-F bond heterolysis to give dissociated ions. The similarity of first-order rates of reaction {2.0 x 10('-5) to 2.5 x 10('-5) sec('-1) at 61(DEGREES)C} in solvents of differing ionizing power (Z-values in the range 54 to 64.2) provides evidence against any heterolytic dissociation mechanism for the isomerization of 3 to 4. The most probable mechanism for the permutational isomerization is concluded to be a nondissociative twist mechanism involving no cleavage of any of the six bonds to tellurium. The isomerization of 13 to a stereoisomer was not observed, either thermally or in the presence of Lewis acids. This could result from a higher activation barrier for the isomerization, or 13 could represent the most thermodynamically stable isomer in the set of possible stereoisomers. The results of complete X-ray crystallographic structure determinations of pertellurane 4 and tellurane 5 are described.","Made available in DSpace on 2014-12-15T23:17:47Z (GMT). No. of bitstreams: 1 8302936.pdf: 4004795 bytes, checksum: c563ee05a959f05eb53e6f07fa8d513e (MD5) Previous issue date: 1982","Embargo set by: Seth Robbins for item 70367 Lift date: Forever Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","U of I Only","138 p.","Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1982."],"dc:identifier":["http://hdl.handle.net/2142/70201","(UMI)AAI8302936"],"dc:subject":["Chemistry, Organic"],"dc:title":["Stereoisomerization of Hexacoordinate Sulfur and Tellurium"],"dc:type":["text"],"thesis:degree_discipline":["Chemistry"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:26:02Z"}