229. Bestimmung des Aggregationsgrads lithiumorganischer Verbindungen durch Kryoskopie in Tetrahydrofuran

Article abstract of DOI:10.1002/hlca.19840670736

The association behaviour of alkyl-, aryl- and alkinyl-lithium compounds as well as of lithium enolates and chiral lithium azaenolates is determined from-freezing point depression values in dilute tetrahydrofuran solutions at -108 grad C.Compared to X-ray-crystallographic data (lithiated methyldithiane, phenyllithium, lithio derivatives of a ketone, carboxylic amide and -ester, and a diketopiperazine-bislactim-ether), desaggregation is found under these conditions.The structutres determined by ¹³C-NMR spectroscopy for BuLi, lithiophenylacetylene and (t-butyl)lithioacetylene are confirmed.The dilithio salt of a carboxylic acid is polymeric, a chiral lithio-hydrazone and a chiral lithio-oxazolidine are monomeric and dimeric, respectively.Lithium diisopropylamide is a monomer-dimer equilibrium mixture.The apparatus described permits both synthesis and measurement of the reactive species under inert atmosphere conditions in the same vessel.