Organometallic exchange reactions. X. Cross-association of tert butyllithium. Kinetics of tert butyllithium dissociation Academic Article uri icon

abstract

  • Intermolecular exchange leading to equilibration of mixtures of t-butyllithium (I) and trimethylsilyl-methyllithium (II) have been studied using 7Li nuclear magnetic resonance. The exchange is rate controlled by dissociation of t-butyllithium tetramers. The first-order rate constant in cyclopentane at 20° is 1 × 10–5 sec–1; the enthalpy of activation is 24 ± 6 kcal/mol. The dissociation is about 20 times more rapid in toluene at 20°. Addition of small quantities of triethylamine to the cyclopentane solutions causes the exchange to become much more rapid; equilibration is achieved in less than 15 min. Mass spectra of samples recovered from cyclopentane solutions made up by mixing I synthesized from 6Li with I synthesized from 7Li exhibit a slow approach to equilibration of the lithium isotopes among the tetramers, commensurate with the nmr results. Mass spectra of samples recovered from mixtures of I with lithium t-butoxide, LiO-t-C4H9, in benzene solution demonstrate the existence of mixed organolithium species in the vapor phase. Similar results were obtained for samples derived from mixtures of I with ethyllithium and with II. © 1970, American Chemical Society. All rights reserved.

published proceedings

  • Journal of the American Chemical Society

altmetric score

  • 3

author list (cited authors)

  • Darensbourg, M. Y., Kimura, B. Y., Hartwell, G. E., & Brown, T. L

citation count

  • 52

complete list of authors

  • Darensbourg, Marcetta Y||Kimura, Bert Y||Hartwell, George E||Brown, Theodore Lawrence

publication date

  • March 1970