The reactive o-quinodimethanes, 1,2-dimethylene-1,2-dihydronaphthalene (9) and o-xylylene (1) were observed by flow [superscript]1H NMR spectroscopy at room temperature. The [superscript]1H NMR spectrum of 9, generated in acetonitrile-d[subscript]3 (CD[subscript]3CN) by fluoride ion induced 1,4-elimination from (1-(trimethylsilylmethyl)) trimethyl(2-naphthylmethyl)ammonium iodide (10), was obtained in the absence of precursor and dimers. However, the [superscript]1H NMR spectrum of the more reactive 1, generated in a similar manner from (o-((trimethylsilyl)methyl)benzyl) trimethylammonium iodide (5), could be obtained only in the presence of its stable (4 + 2) and (4 + 4) dimers;The dimerization kinetics of 3-methyl-(5[superscript]'), 3,6-dimethyl-(11), 3-isopropyl-(12), and 3,6-diisopropyl-1,2-xylylene (13) in acetonitrile (CH[subscript]3CN) were studied by stopped-flow UV-visible spectroscopy. These reactive o-quinodimethanes were generated by fluoride ion induced elimination from the appropriate amine salt precursors. The dimerization rates (25°C) for each of these is somewhat slower than that of o-xylylene (1) itself (k[subscript] 5[superscript]'/k[subscript]1 = 0.92, k[subscript]11/k[subscript]1 = 0.42, k[subscript]12/k[subscript]1 = 0.44, and k[subscript]13/k[subscript]1 = 0.02). The dimerization of the unsymmetrical 5[superscript]' and 12 resulted in formation of all four possible (4 + 2) dimers for each. Dimerization of the symmetrical 11 and 13 gave only (4 + 2) dimer for each. In all cases, little or none of the respective (4 + 4) dimer was formed. The [superscript]1H NMR spectra for 5[superscript]' and 11-13 were also observed in CD[subscript]3CN by flow [superscript]1H NMR spectroscopy;Fluoride ion induced 1,2-elimination from 2-trimethylsilylbenzocyclobutenyl-1 mesylate (26) was used to generate the reactive molecule benzocyclobutadiene (1[superscript]') in CD[subscript]3CN, which was observed by flow [superscript]1H NMR spectroscopy at room temperature. The signal for the 4-membered ring protons of 1[superscript]' is at 6.36 ppm, while the multiplets for the 6-membered ring protons are at 6.26 and 5.78 ppm. Based on the positions of the [superscript]1H NMR signals, 1[superscript]' appears to be nonaromatic and not aromatic or antiaromatic;The [superscript]1H NMR spectrum (in CD[subscript]3CN) of 1,2-dimethylene-1,2-dihydrothiophene (1[superscript]''), obtained by fluoride ion induced 1,4-elimination from 3-(trimethylammonium-methyl)-2-(trimethylsilylmethyl)thiophene iodide (11[superscript]'), was observed by flow [superscript]1H NMR spectroscopy at room temperature. The dimerization rate of 1[superscript]'' in CH[subscript]3CN, generated in the same manner, was measured by UV-visible spectroscopy (k[subscript] 1[superscript]'' = 10.8 M[superscript]-1 s[superscript]-1, at 25°C). The reactivity of 1[superscript]'' is thus intermediate between o-xylylene (1) and 1,2-dimethylene-1,2-dihydrofuran (9).
","abstract_html":"<p>The reactive o-quinodimethanes, 1,2-dimethylene-1,2-dihydronaphthalene (9) and o-xylylene (1) were observed by flow [superscript]1H NMR spectroscopy at room temperature. The [superscript]1H NMR spectrum of 9, generated in acetonitrile-d[subscript]3 (CD[subscript]3CN) by fluoride ion induced 1,4-elimination from (1-(trimethylsilylmethyl)) trimethyl(2-naphthylmethyl)ammonium iodide (10), was obtained in the absence of precursor and dimers. However, the [superscript]1H NMR spectrum of the more reactive 1, generated in a similar manner from (o-((trimethylsilyl)methyl)benzyl) trimethylammonium iodide (5), could be obtained only in the presence of its stable (4 + 2) and (4 + 4) dimers;The dimerization kinetics of 3-methyl-(5[superscript]'), 3,6-dimethyl-(11), 3-isopropyl-(12), and 3,6-diisopropyl-1,2-xylylene (13) in acetonitrile (CH[subscript]3CN) were studied by stopped-flow UV-visible spectroscopy. These reactive o-quinodimethanes were generated by fluoride ion induced elimination from the appropriate amine salt precursors. The dimerization rates (25°C) for each of these is somewhat slower than that of o-xylylene (1) itself (k[subscript] 5[superscript]'/k[subscript]1 = 0.92, k[subscript]11/k[subscript]1 = 0.42, k[subscript]12/k[subscript]1 = 0.44, and k[subscript]13/k[subscript]1 = 0.02). The dimerization of the unsymmetrical 5[superscript]' and 12 resulted in formation of all four possible (4 + 2) dimers for each. Dimerization of the symmetrical 11 and 13 gave only (4 + 2) dimer for each. In all cases, little or none of the respective (4 + 4) dimer was formed. The [superscript]1H NMR spectra for 5[superscript]' and 11-13 were also observed in CD[subscript]3CN by flow [superscript]1H NMR spectroscopy;Fluoride ion induced 1,2-elimination from 2-trimethylsilylbenzocyclobutenyl-1 mesylate (26) was used to generate the reactive molecule benzocyclobutadiene (1[superscript]') in CD[subscript]3CN, which was observed by flow [superscript]1H NMR spectroscopy at room temperature. The signal for the 4-membered ring protons of 1[superscript]' is at 6.36 ppm, while the multiplets for the 6-membered ring protons are at 6.26 and 5.78 ppm. Based on the positions of the [superscript]1H NMR signals, 1[superscript]' appears to be nonaromatic and not aromatic or antiaromatic;The [superscript]1H NMR spectrum (in CD[subscript]3CN) of 1,2-dimethylene-1,2-dihydrothiophene (1[superscript]''), obtained by fluoride ion induced 1,4-elimination from 3-(trimethylammonium-methyl)-2-(trimethylsilylmethyl)thiophene iodide (11[superscript]'), was observed by flow [superscript]1H NMR spectroscopy at room temperature. The dimerization rate of 1[superscript]'' in CH[subscript]3CN, generated in the same manner, was measured by UV-visible spectroscopy (k[subscript] 1[superscript]'' = 10.8 M[superscript]-1 s[superscript]-1, at 25°C). The reactivity of 1[superscript]'' is thus intermediate between o-xylylene (1) and 1,2-dimethylene-1,2-dihydrofuran (9).</p>","abstract_has_math":false,"creators":["Fischer, David"],"institution":null,"degree_name":"Doctor of Philosophy","degree_level":"dissertation","degree_discipline":null,"degree_department":"Department of Chemistry","school":null,"contributors":[],"advisors":["Walter S. Trahanovsky"],"committee_chairs":[],"committee_members":[],"year":1990,"date_issued":"1990","date_published":"1990","updated_at":"2026-07-24T02:38:57Z","subjects":[],"languages":["en"],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier.doi","label":"DOI","values":["https://doi.org/10.31274/rtd-180813-11798"],"render_values":[{"text":"https://doi.org/10.31274/rtd-180813-11798","href":"https://doi.org/10.31274/rtd-180813-11798","code":true}]},{"key":"dc:identifier","label":"Identifier","values":["archive/lib.dr.iastate.edu/rtd/9398/"],"render_values":[{"text":"archive/lib.dr.iastate.edu/rtd/9398/","href":null,"code":true}]}]},"links":{"outbound_url":"https://dr.lib.iastate.edu/handle/20.500.12876/82492","outbound_label":"Repository record","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Walter S. Trahanovsky"]},{"key":"dc:contributor.department","label":"Department","values":["Department of Chemistry"]},{"key":"dc:creator","label":"Author","values":["Fischer, David"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2018-08-15T13:45:28.000"]},{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2020-07-02T06:13:14Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2020-07-02T06:13:14Z"]},{"key":"dc:date.issued","label":"Date","values":["1990"]},{"key":"dc:type","label":"Dc Type","values":["dissertation"]},{"key":"thesis:degree_level","label":"Degree Level","values":["dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Doctor of Philosophy"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["archive/lib.dr.iastate.edu/rtd/9398/"]},{"key":"dc:identifier.doi","label":"DOI","values":["https://doi.org/10.31274/rtd-180813-11798"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://dr.lib.iastate.edu/handle/20.500.12876/82492"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The reactive o-quinodimethanes, 1,2-dimethylene-1,2-dihydronaphthalene (9) and o-xylylene (1) were observed by flow [superscript]1H NMR spectroscopy at room temperature. The [superscript]1H NMR spectrum of 9, generated in acetonitrile-d[subscript]3 (CD[subscript]3CN) by fluoride ion induced 1,4-elimination from (1-(trimethylsilylmethyl)) trimethyl(2-naphthylmethyl)ammonium iodide (10), was obtained in the absence of precursor and dimers. However, the [superscript]1H NMR spectrum of the more reactive 1, generated in a similar manner from (o-((trimethylsilyl)methyl)benzyl) trimethylammonium iodide (5), could be obtained only in the presence of its stable (4 + 2) and (4 + 4) dimers;The dimerization kinetics of 3-methyl-(5[superscript]'), 3,6-dimethyl-(11), 3-isopropyl-(12), and 3,6-diisopropyl-1,2-xylylene (13) in acetonitrile (CH[subscript]3CN) were studied by stopped-flow UV-visible spectroscopy. These reactive o-quinodimethanes were generated by fluoride ion induced elimination from the appropriate amine salt precursors. The dimerization rates (25°C) for each of these is somewhat slower than that of o-xylylene (1) itself (k[subscript] 5[superscript]'/k[subscript]1 = 0.92, k[subscript]11/k[subscript]1 = 0.42, k[subscript]12/k[subscript]1 = 0.44, and k[subscript]13/k[subscript]1 = 0.02). The dimerization of the unsymmetrical 5[superscript]' and 12 resulted in formation of all four possible (4 + 2) dimers for each. Dimerization of the symmetrical 11 and 13 gave only (4 + 2) dimer for each. In all cases, little or none of the respective (4 + 4) dimer was formed. The [superscript]1H NMR spectra for 5[superscript]' and 11-13 were also observed in CD[subscript]3CN by flow [superscript]1H NMR spectroscopy;Fluoride ion induced 1,2-elimination from 2-trimethylsilylbenzocyclobutenyl-1 mesylate (26) was used to generate the reactive molecule benzocyclobutadiene (1[superscript]') in CD[subscript]3CN, which was observed by flow [superscript]1H NMR spectroscopy at room temperature. The signal for the 4-membered ring protons of 1[superscript]' is at 6.36 ppm, while the multiplets for the 6-membered ring protons are at 6.26 and 5.78 ppm. Based on the positions of the [superscript]1H NMR signals, 1[superscript]' appears to be nonaromatic and not aromatic or antiaromatic;The [superscript]1H NMR spectrum (in CD[subscript]3CN) of 1,2-dimethylene-1,2-dihydrothiophene (1[superscript]''), obtained by fluoride ion induced 1,4-elimination from 3-(trimethylammonium-methyl)-2-(trimethylsilylmethyl)thiophene iodide (11[superscript]'), was observed by flow [superscript]1H NMR spectroscopy at room temperature. The dimerization rate of 1[superscript]'' in CH[subscript]3CN, generated in the same manner, was measured by UV-visible spectroscopy (k[subscript] 1[superscript]'' = 10.8 M[superscript]-1 s[superscript]-1, at 25°C). The reactivity of 1[superscript]'' is thus intermediate between o-xylylene (1) and 1,2-dimethylene-1,2-dihydrofuran (9).
"]},{"key":"dc:format.mimetype","label":"Dc Format Mimetype","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Observation by flow 1H NMR and dimerization kinetics and products of reactive ortho-quinodimethanes and benzocyclobutadiene"]}]}],"canonical_facts":{"dc:contributor.advisor":["Walter S. Trahanovsky"],"dc:contributor.department":["Department of Chemistry"],"dc:creator":["Fischer, David"],"dc:date":["2018-08-15T13:45:28.000"],"dc:date.accessioned":["2020-07-02T06:13:14Z"],"dc:date.available":["2020-07-02T06:13:14Z"],"dc:date.issued":["1990"],"dc:description.abstract":["The reactive o-quinodimethanes, 1,2-dimethylene-1,2-dihydronaphthalene (9) and o-xylylene (1) were observed by flow [superscript]1H NMR spectroscopy at room temperature. The [superscript]1H NMR spectrum of 9, generated in acetonitrile-d[subscript]3 (CD[subscript]3CN) by fluoride ion induced 1,4-elimination from (1-(trimethylsilylmethyl)) trimethyl(2-naphthylmethyl)ammonium iodide (10), was obtained in the absence of precursor and dimers. However, the [superscript]1H NMR spectrum of the more reactive 1, generated in a similar manner from (o-((trimethylsilyl)methyl)benzyl) trimethylammonium iodide (5), could be obtained only in the presence of its stable (4 + 2) and (4 + 4) dimers;The dimerization kinetics of 3-methyl-(5[superscript]'), 3,6-dimethyl-(11), 3-isopropyl-(12), and 3,6-diisopropyl-1,2-xylylene (13) in acetonitrile (CH[subscript]3CN) were studied by stopped-flow UV-visible spectroscopy. These reactive o-quinodimethanes were generated by fluoride ion induced elimination from the appropriate amine salt precursors. The dimerization rates (25°C) for each of these is somewhat slower than that of o-xylylene (1) itself (k[subscript] 5[superscript]'/k[subscript]1 = 0.92, k[subscript]11/k[subscript]1 = 0.42, k[subscript]12/k[subscript]1 = 0.44, and k[subscript]13/k[subscript]1 = 0.02). The dimerization of the unsymmetrical 5[superscript]' and 12 resulted in formation of all four possible (4 + 2) dimers for each. Dimerization of the symmetrical 11 and 13 gave only (4 + 2) dimer for each. In all cases, little or none of the respective (4 + 4) dimer was formed. The [superscript]1H NMR spectra for 5[superscript]' and 11-13 were also observed in CD[subscript]3CN by flow [superscript]1H NMR spectroscopy;Fluoride ion induced 1,2-elimination from 2-trimethylsilylbenzocyclobutenyl-1 mesylate (26) was used to generate the reactive molecule benzocyclobutadiene (1[superscript]') in CD[subscript]3CN, which was observed by flow [superscript]1H NMR spectroscopy at room temperature. The signal for the 4-membered ring protons of 1[superscript]' is at 6.36 ppm, while the multiplets for the 6-membered ring protons are at 6.26 and 5.78 ppm. Based on the positions of the [superscript]1H NMR signals, 1[superscript]' appears to be nonaromatic and not aromatic or antiaromatic;The [superscript]1H NMR spectrum (in CD[subscript]3CN) of 1,2-dimethylene-1,2-dihydrothiophene (1[superscript]''), obtained by fluoride ion induced 1,4-elimination from 3-(trimethylammonium-methyl)-2-(trimethylsilylmethyl)thiophene iodide (11[superscript]'), was observed by flow [superscript]1H NMR spectroscopy at room temperature. The dimerization rate of 1[superscript]'' in CH[subscript]3CN, generated in the same manner, was measured by UV-visible spectroscopy (k[subscript] 1[superscript]'' = 10.8 M[superscript]-1 s[superscript]-1, at 25°C). The reactivity of 1[superscript]'' is thus intermediate between o-xylylene (1) and 1,2-dimethylene-1,2-dihydrofuran (9).
"],"dc:format.mimetype":["application/pdf"],"dc:identifier":["archive/lib.dr.iastate.edu/rtd/9398/"],"dc:identifier.doi":["https://doi.org/10.31274/rtd-180813-11798"],"dc:identifier.uri":["https://dr.lib.iastate.edu/handle/20.500.12876/82492"],"dc:language.iso":["en"],"dc:title":["Observation by flow 1H NMR and dimerization kinetics and products of reactive ortho-quinodimethanes and benzocyclobutadiene"],"dc:type":["dissertation"],"thesis:degree_level":["dissertation"],"thesis:degree_name":["Doctor of Philosophy"]},"updated_at":"2026-07-24T02:38:57Z"}