Structures of Linear Poly(ethylene oxide) Compounds and Potassium Complexes in Dichloromethane

Abstract

The H-1 NMR spectra of a series of linear poly(ethylene oxides) compounds (POE compounds) were measured in dichloromethane-d2 at 25 degrees C, where the POE compounds (HO-(CH2CH2O-)n-R) were unsubstituted POE, HEOn (R=H, n=3, 4, 6), and alkyl-substituted POE, DEOn (R=C12H25, n=4, 6, 8) and MeEO6 (R=CH3, n=6). All the peaks of H-1 NMR signals were assigned to each methylene proton of POE. The chemical shifts and coupling constant between vicinal protons were evaluated by a complete spin analysis. The spectral changes of POE compounds by the addition of potassium ion were measured at various metal-to-POE ratios. The chemical shift change of each methylene proton by the formation of the complex was evaluated. The downfield shift of methylene protons caused by the complex formation indicates that the ethylene oxide that the ethylene oxide moiety is coordinating to surround the potassium ion in the same manner as the cyclic crown ether complexes. The results of spin lattice relaxation time measurements of DEO6 suggest that all the methylenes of the ethylene oxides are immobilized by the coordination to the metal ion. Thus, it was confirmed that all oxygens of POE are participating in the complex formation.