Thermal isomerization and decomposition of ethynyldisilanes

dc.contributor.author Petrich, Scott
dc.contributor.department Chemistry
dc.date 2018-08-23T07:24:47.000
dc.date.accessioned 2020-06-30T07:04:02Z
dc.date.available 2020-06-30T07:04:02Z
dc.date.copyright Wed Jan 01 00:00:00 UTC 1992
dc.date.issued 1992
dc.description.abstract <p>Co-pyrolysis of ethynylpentamethyldisilane with 2,3-dimethylbutadiene afforded trimethylsilylacetylene, dimethylsily(trimethylsilyl)acetylene and 1,1,3,4-tetramethyl-1-silacyclopent-3-ene. When an alkyl or trimethylsilyl substituted ethynyl group was pyrolyzed, extrusion of dimethylsilylene was the only decomposition process observed with no isomerization. The decomposition and isomerization pathways were proposed to proceed via a silacyclopropene intermediate. Arrhenius parameters were determined for these processes by using a pulse stirred-flow reactor. The substitution on the silacyclopropene intermediate determined which pathway would be favored. When a good migrating group was on the silicon in the silacyclopropene, a vinylsilylene intermediate was also involved. The decomposition via a silacyclopropene competed with an [alpha]-elimination when both were possible;Pyrolysis of ethynylundecamethylcyclohexasilane afforded the ring-expanded isomer 3-hydridoundecamethylhexasilacyclooctyne and decamethylpentasilacycloheptyne. Pyrolysis of 4,4,5,5,6,6,7,7,8,8-decamethyl-4,5,6,7,8-pentasilacyclooctyne afforded ring-contracted isomer 1,1-penta(dimethylsilylene)propadiene, 4,4,5,5,6,6,7,7-octamethyl-4,5,6,7-tetrasilacycloheptyne, 1, and 1,1-tetra(dimethylsilylene)propadiene, 2. Cycloheptyne 1 was also pyrolyzed and afforded propadiene 2 as the only product. Several mechanisms were proposed for these decompositions and isomerizations. The pathways involving a loss of dimethylsilylene were proposed to proceed through a silacyclopropene intermediate. The isomerizations were proposed to go through a cyclopropene intermediate;Bis (1,3-tetra(dimethylsilylene)) propadiene, 3, was synthesized from cycloheptyne 1 in 20% yield. An x-ray structure of the smallest "betweenallene", 3, was determined. The propadiene carbons were linear and twisted 18 degrees towards planarity. Pyrolysis of propadiene 3 afforded isomer 1,1-3,3-bis(tetra(dimethylsilylene)) propadiene as the only observed product. The proposed mechanism involved cyclopropene intermediates.</p>
dc.format.mimetype application/pdf
dc.identifier archive/lib.dr.iastate.edu/rtd/10340/
dc.identifier.articleid 11339
dc.identifier.contextkey 6399848
dc.identifier.doi https://doi.org/10.31274/rtd-180813-13102
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath rtd/10340
dc.identifier.uri https://dr.lib.iastate.edu/handle/20.500.12876/63476
dc.language.iso en
dc.source.bitstream archive/lib.dr.iastate.edu/rtd/10340/r_9234843.pdf|||Fri Jan 14 18:19:04 UTC 2022
dc.subject.disciplines Organic Chemistry
dc.subject.keywords Chemistry
dc.subject.keywords Organic chemistry
dc.title Thermal isomerization and decomposition of ethynyldisilanes
dc.type article
dc.type.genre dissertation
dspace.entity.type Publication
relation.isOrgUnitOfPublication 42864f6e-7a3d-4be3-8b5a-0ae3c3830a11
thesis.degree.level dissertation
thesis.degree.name Doctor of Philosophy
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