Polyether-phenol complex

Solutes held firmly in the vehicle exhibit low activity coefficients (low escaping tendencies) and thus low rates of penetration. Differences occur in the activity of phenols in mineral oil and polypropylene glycol bases. The latter are bland, the former corrosive. Polyether-phenol complex formation decreases the thermodynamic activity of the phenols, which are therefore less toxic. 

Also of interest is the oxidative polycondensation of 2,6-disubstituted phenols with transition metal catalysts such as palladium complexes, which produces aromatic polyethers [2]. 

If traces of transitional metals are present accidentally (Fe3+, Cr2+, Ni2+) in the polyether polyols, these ions interact with the antioxidants and give chromophoric substances by complexation with hindered phenols or with the alkylated diphenylamines. 

A number of reports [10, 17, 22, 25-27] suggest that, in the case of condensation between aromatic diols and polyethylene glycols, the nature of the template exerts an influence on the rate of macrocyclisation. The templates form various series depending on the size of the synthesised crown ether, but lithium ion is an inhibitor in all cases. This must be attributed to the fact that Li+ forms the most stable ion pair with phenolate and simultaneously gives the least stable complexes with benzo crown ethers. It should be noted that alkaline earth metal ions, even in small concentrations, promote these reaction more effectively than alkali metal ions. In addition, it has been emphasised [12] that there is a definite correlation between the basicity of the substance used in the template synthesis of macrocyclic polyethers and the yield of final product. 

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