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RESEARCH PRODUCT
On the anionic polymerization of dialkylaminoisoprenes, 3. A nuclear magnetic resonance study of the structure of oligo[5-(N,N-diisopropylamino)isoprenyllithium]
Reimund StadlerHeinz KolshornCesar Liberato Petzholdsubject
Polymers and PlasticsOrganic ChemistrySolution polymerizationDegree of polymerizationCondensed Matter Physicschemistry.chemical_compoundAnionic addition polymerizationchemistryPolymer chemistryMaterials ChemistryPhysical and Theoretical ChemistrySolvent effectsIsomerizationTetrahydrofuranIsopropylCarbaniondescription
The structure of oligo[(5-N,N-diisopropylamino)isoprenyllithium] (number-average degree of polymerization Pn = 1-2) prepared by reaction of alkyllithium with 5-(N,N-diisopropylamino)-isoprene1 in nonpolar (benzene) and polar (tetrahydrofuran) solvents has been studied by 1H and 13C NMR spectroscopy. In tetrahydrofuran, as expected, the negative charge at the terminal chain unit is more delocalized than in benzene and, consequently, the carbon-lithium bond has a more ionic character. In both solvents the living chain end shows a cisoid-4, 1-structure. No cistrans isomerization could be detected. This independence of the carbanion structure of the solvent polarity is explained by the complexation of the Li+ counter ion to the amino group of the terminal monomer unit and by the bulkiness of the isopropyl side groups, which hinder isomerization and favour the cisoid conformation of the living chain end.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 1995-05-01 | Macromolecular Chemistry and Physics |