A kinetic study of sodium cation migration in 2,5-di-tert-butyl-1,4- benzoquinone radical anion in the presence of crown ethers as studied with high-pressure electron spin resonance

The effects of crown ethers were examined for the intramolecular two-site jumping rates of sodium cations in 2,5-ditert-1,4-benzoquinone ion pairs using a high-pressure electron spin resonance (ESR) technique. The activation volumes for the intramolecular migration of the sodium cation (ΔV> ₁‡) and the inclusion complex of the sodium cation with crown ethers (ΔV₂‡) were estimated to be -7.4 and 9.5-13.8 cm²3 mol^-1, respectively. Further, the reaction volumes (ΔV) for the Na⁺/crown-ether complex formation were determined as 15.6-17.5 cm³ mol^-1 in 1,2-dimethoxyethane. Based on the results, the mechanism for intramolecular sodium cation migration in the presence of crown ethers is discussed from the perspective of volume.