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Bestimmung des Aggregationsgrads lithiumorganischer Verbindungen durch Kryoskopie in Tetrahydrofuran
Author(s) -
Bauer Walter,
Seebach Dieter
Publication year - 1984
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19840670736
Subject(s) - chemistry , tetrahydrofuran , lithium diisopropylamide , dimer , ether , monomer , ketone , phenyllithium , polymer chemistry , medicinal chemistry , lithium (medication) , alkyl , organic chemistry , polymer , ion , solvent , deprotonation , medicine , endocrinology
Degree of Aggregation of Organolithium Compounds by Means of Cryoscopy in Tetrahydrofuran 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°C. Compared toX‐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 structures determined by 13 C‐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.