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

Abstract

Abstract1H 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.