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Solution‐Structure and Aggregation Behavior of Two Dilithiostyrene Derivatives
Author(s) -
Günther Harald,
Eppers Oswald,
Hausmann Heike,
Hüls Dietmar,
Mons HansEgbert,
Klein KlausDieter,
Maercker Adalbert
Publication year - 1995
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.19950780804
Subject(s) - chemistry , homonuclear molecule , dimer , monomer , dimethoxyethane , crystallography , nuclear magnetic resonance spectroscopy , stereochemistry , molecule , polymer , organic chemistry , electrode , electrolyte
The solution structure and the aggregation behavior of ( E )‐2‐lithio‐1‐(2‐lithiophenyl)‐1‐phenylpent‐1‐ene ( 1 ) and ( Z )‐2‐lithio‐1‐(2‐lithiophenyl)ethene ( 2 ) were investigated by one‐ and two‐dimensional 1 H‐, 13 C‐, and 6 Li‐NMR spectroscopy. In Et 2 O, both systems form dimers which show homonuclear scalar 6 Li, 6 Li spin‐spin coupling. In the case of 2 , extensive 6 Li, 1 H coupling is observed. In tetrahdrofuran and in the presence of 2 mol of N , N , N′ , N′ ‐tetramethylethylylenediamine (tmeda), the dimeric structure of 1 coexists with a monomer. The activation parameters for intra ‐aggregate exchange in the dimers of 1 and 2 ( 1 (Et 2 O): Δ H ≠ = 62.6 ± 13.9 kJ/mol, Δ S ≠ = 5.8 ± 14.0 J/mol K, Δ G ≠(263) = 61.1 kJ/mol; 2 (dimethoxyethane): Δ H ≠ = 36.9 ± 6.5 kJ/mol, Δ S ≠ = −61 ± 25 J/mol K, Δ G ≠(263) = 54.0 kJ/mol) and the thermodynamic parameters for the dimer‐monomer equilibrium for 1 (Δ H °; = 26.7 ± 5.5 kJ/mol, Δ S ° = 63 ± 27 J/mol K), where the monomer is favored at low temperature, were determined by dynamic NMR studies.