Ion pairing of 1,5-diarylpentadienyl carbanions

Abstract

The 1,5-diarylpentadienyl carbanions exist in solution as mixtures of tight and loose ion pairs. The thermodynamic parameters for the change tight → loose ion pair have been determined for several combinations of solvent and counterion. The introduction into the rings of electron-releasing substituents increases the magnitude of ΔH and ΔS; a similar effect is produced by increasing the chain length from pentadiene to heptatriene and nonatetraene.