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- W2002604145 abstract "Abstract Cyclic oligomers (I, R′ = H) obtained from the base-catalyzed reaction of p-substituted phenols and formaldehyde are an old class of compounds [1] which are experiencing new interest because of their cone-shape that brought them the name of calixarenes [2]. The tetramer (II) we isolated from the reaction of p-t-butylphenol and formaldehyde forms a stable 1:1 chlatrate of cage-type with toluene which is held into the cavity as guest [3]. Chlatrates, whose structures are under investigation, are also formed by the octamer (III) which has been isolated from the same reaction mixture. Both compounds have been used as ordered building blocks for open chain cation ligands [4] obtained by alkylation of the phenolic OH with different binding groups [I, R′ = CH3, CH3CO, (CH2CH2)(n)-CH3]. The alkylation of II and Ill destroys the cup-like structure of the starting compounds, which is mainly determined by intramolecular hydrogen bonds, giving products with different geometries and complexing abilities toward cations. Derivatives of the tetrameric oligomer (II) are a mixture of stereoisomers which do not interconvert at ambient temperature and have non convergent binding groups. Their complexation toward Li+, Na+, K+,NH+4, [C(NH2)3]+picrates is very poor, these salts being not extracted by the ligands from water to CDCl3 and CH2Cl2. Derivatives of the octamer (III) have chains which easily pass through the central hole and are able to wrap the cations as the octopus molecules [4]. Methyl and acetyl derivatives of III do not complex any tested cation, while compounds with even short poliethers chains [I, R′ = CH2CH2OCH3, (CH2-CH2O)2CH3] are able to extract picrates from water to CH2Cl2 and CDCl3. A remarkable strong complexation of the latter compounds is observed toward guanidinium cation whose tetraphenylborate is dissolved in CDCl3 up to a ratio [salt]/[ligand] = 1.3−1.5 and picrate extracted from H2O to CH2Cl2 with an extraction constant Ke ⋍ 2× 104 M−2. Results obtained with other ligands built on cyclic oligomers derived from p-cresol and p-octylphenol will be also reported." @default.
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- W2002604145 date "1980-01-01" @default.
- W2002604145 modified "2023-10-16" @default.
- W2002604145 title "Complexing properties of phenol—formaldehyde cyclic oligomers and their derivatives" @default.
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- W2002604145 doi "https://doi.org/10.1016/s0020-1693(00)92242-4" @default.
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