Nuclear magnetic resonance studies on polymer carbanions, 2. Model compounds for α-methylstyrene and α-methylstyrene tetramer dianions

¹H and ¹³C NMR spectra of model compounds for the poly-α-methylstyryl anion, 2-lithio, 2-potassio, and 2-cesio-2-phenylbutane, were determined. The lithium compound had a higher charge density at the α-carbon and a lower charge on the phenyl ring than the other compounds and exhibited phenyl ring rotation at higher temperatures. The activation energy was calculated to be 61, 0 kJ/mol. The potassium and cesium compounds did not show phenyl ring rotation at 80°C. Quantum chemical calculations indicated that the larger cations interact with the phenyl ring especially with the ortho carbons. ¹³C NMR spectra of α-methylstyrene tetramer dianion with sodium and potassium as counter cation were also measured and compared with those of the model compounds.