An NMR Study of Trimethylsilylmethyllithium Aggregates and Mixed Trimethylsilylmethyllithium/Lithium trimethylsilylmethoxide Aggregates

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Description:

An NMR spectroscopy study of trimethylsilylmethyllilthium, TMSM-Li, indicates that TMSM-Li exists as two different aggregates in cyclopentane solution. Using previously reported colligative properties of TMSM-Li in different solutions in connection with new 13C and 6Li NMR data collected in this study, aggregation states were assigned as octamer and hexamer. Low temperature 13C and 6Li NMR peak intensities indicated an equilibrium exists between the two aggregates that shifts toward the octamer as the temperature decreases. ΔH was calculated to be 5.23 + 0.15 kcal/mol and ΔS was calculated to be 17.9 + 0.6 eu for the hexamer/octamer equilibrium system. Samples of TMSM-Li were mixed with TMSM-OH in attempts to form mixed alkyllithium/lithium alkoxide aggregates. 13C NMR data for these mixtures gave inconclusive results whether or not these compounds formed, which is different from other primary alkyllithium compounds studied in the past. A study of neopentyllithium, NpLi, indicates only one aggregate in solution with the aggregation state unknown using low temperature 13C NMR spectroscopy.

Creator(s): Medley, Marilyn S.
Creation Date: December 2004
Partner(s):
UNT Libraries
Collection(s):
UNT Theses and Dissertations
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Publisher Info:
Publisher Name: University of North Texas
Place of Publication: Denton, Texas
Date(s):
  • Creation: December 2004
  • Digitized: December 7, 2007
Description:

An NMR spectroscopy study of trimethylsilylmethyllilthium, TMSM-Li, indicates that TMSM-Li exists as two different aggregates in cyclopentane solution. Using previously reported colligative properties of TMSM-Li in different solutions in connection with new 13C and 6Li NMR data collected in this study, aggregation states were assigned as octamer and hexamer. Low temperature 13C and 6Li NMR peak intensities indicated an equilibrium exists between the two aggregates that shifts toward the octamer as the temperature decreases. ΔH was calculated to be 5.23 + 0.15 kcal/mol and ΔS was calculated to be 17.9 + 0.6 eu for the hexamer/octamer equilibrium system. Samples of TMSM-Li were mixed with TMSM-OH in attempts to form mixed alkyllithium/lithium alkoxide aggregates. 13C NMR data for these mixtures gave inconclusive results whether or not these compounds formed, which is different from other primary alkyllithium compounds studied in the past. A study of neopentyllithium, NpLi, indicates only one aggregate in solution with the aggregation state unknown using low temperature 13C NMR spectroscopy.

Degree:
Level: Master's
Discipline: Inorganic Chemistry
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Subject(s):
Keyword(s): NMR study | organolithium | trimethylsilylmethyl
Contributor(s):
Partner:
UNT Libraries
Collection:
UNT Theses and Dissertations
Identifier:
  • OCLC: 58796381 |
  • ARK: ark:/67531/metadc4657
Resource Type: Thesis or Dissertation
Format: Text
Rights:
Access: Use restricted to UNT Community
License: Copyright
Holder: Medley, Marilyn S.
Statement: Copyright is held by the author, unless otherwise noted. All rights reserved.