On the Acidity of the Hydroxyl Groups in Calix[4]arenes and the Dissociation-dependent Conformational Change

Shinkai, Seiji; Araki, Koji; Koreishi, Hiroshi; Tsubaki, Takayuki; Manabe, Osamu

doi:10.1246/cl.1986.1351

Cited by 47 publications

(21 citation statements)

References 5 publications

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“…As shown by Shinkai et al, 32 the same effect is observed for sodium p-sulfonate calix [4]arene salt relative to that of the corresponding noncyclic monomer. These authors also found that the methylene hydrogens of the oxy-anions formed by the dissociation of the hydroxyl groups of p-sulfonate calix [4]arene give a pair of doublets in the NMR spectrum, which is due to a more rigid conic conformation that resulted from the strong intramolecular hydrogen bonding.…”

Section: Effect Of Water On the Activity Of Organocatalysts I And Iisupporting

confidence: 66%

p-Sulfonic acid calix[n]arenes: the most active and water tolerant organocatalysts in esterification reactions

Natalino

Varejão

Silva

et al. 2014

Catal. Sci. Technol.

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This work reports the novel results obtained from an in situ kinetic study, which was conducted via 1 H NMR, of the palmitic acid esterification reaction with deuterated methanol in the presence of organocatalysts: p-sulfonic acid calix[6]arene, p-hydroxybenzenesulfonic acid and p-toluenesulfonic acid. The kinetic order of reaction relative to the catalyst concentration and the main thermodynamic properties, such as the activation energy (ΔE), entropy variation (ΔS), enthalpy variation (ΔH) and Gibbs free energy variation (ΔG), were obtained. The results indicated that p-sulfonic acid calix[6]arene was the most active organocatalyst in esterification reactions, regardless of temperature or catalyst concentration employed. Additionally, by performing the reactions in the presence of increasing amounts of water, it was found that p-sulfonic acid calix[n]arenes are more tolerant to water than the other catalysts investigated.This result, when combined with the kinetic and thermodynamic measurements, may explain their highest catalytic activity.

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Section: Effect Of Water On the Activity Of Organocatalysts I And Iisupporting

confidence: 66%

p-Sulfonic acid calix[n]arenes: the most active and water tolerant organocatalysts in esterification reactions

Natalino

Varejão

Silva

et al. 2014

Catal. Sci. Technol.

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“…17 At pH 1 and 5, the binding of 1 to lysine and arginine causes large changes in the chemical shifts of the protons of the amino acid lateral chains. All peaks shift to higher magnetic field with increasing calixarene concentration.…”

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confidence: 99%

Complexation of basic amino acids by water-soluble calixarene sulphonates as a study of the possiblemechanisms of recognition of calixarene sulphonates by proteins

Douteau‐Guével

Coleman

Morel

et al. 1998

J. Phys. Org. Chem.

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The interactions of calixarene sulphonates with the basic amino acids arginine and lysine were studied by 1 H NMR spectroscopy. Strong electrostatic binding occurs for calix [4]arene sulphonate with both lysine and arginine at pH 1 and 5. For the higher calixarenes, only weak interactions at the faces of the flattened macrocycles occur. This binding is in contrast to the inhibition of protein-protein interactions by the calixarenes where the calix[6]arene and calix [8]arene sulphonates show much stronger effects.

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“…In addition, the phenolic groups at the lower rim of the calixarene are likely in parts dissociated in MeOH because pK a3 in aqueous medium is 4.0 whereas the last proton has a much higher pK a4 . 11 [44]. Therefore, this calixarene has an advantageous ratio between the hydrodynamic radius and the effective charge.…”

Section: Electrophoretic Mobility Of Calixarenes and Resorcinarenesmentioning

confidence: 99%

Separation of (Z)‐ and (E)‐isomers of thioxanthene and dibenz[b,e]oxepin derivatives with calixarenes and resorcinarenes as additives in nonaqueous capillary electrophoresis

Sokoließ¹,

Gronau²,

Menyes³

et al. 2003

Electrophoresis

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Five acidic calix[4]arenes with carboxylic or sulfonic groups at either the upper or lower rim of the cavity and one resorc[4]arene were investigated to separate three thioxanthenes (flupentixol, clopenthixol, chlorprothixene) and a dibenz[b,e]oxepin derivative (doxepin) with cis-/trans-isomerism by nonaqueous capillary electrophoresis (NACE). Partial filling of the capillary with the UV-absorbing selectors led to a low detection limit and an advantageous signal-to-noise ratio (S/N). A sufficient electrophoretic mobility of the calixarenes towards the anode was necessary to outweigh the oppositely directed electroosmotic flow (EOF). This depended from the functional groups, the dissociation and the hydrodynamic radius of the cyclophanes. In contrast, the resorcinarene was useable only by addition of sodium dodecyl sulfate (SDS) because only the complex of the two selectors had an anodic apparent electrophoretic mobility. p-Sulfonyl-calix[4]arene (ss-a1) was the most capable selector for all E/Z-isomers with maximal alpha-values ranging from 1.056 for doxepin to 1.224 for chlorprothixene. This was due to the sufficient migration in reversed direction to the EOF even at low pH* values of 3.0. Otherwise, electrostatic as well as hydrophobic interactions with the positively charged isomers seem to contribute to a superior recognition. Increasing the concentration up to 15 mM ss-a1 and using acidic media (pH* 5.0) led to high separation efficiency. Changing the organic solvent provides a powerful tool to improve selectivity with N,N-dimethylformamide-methanol (DMF-MeOH)-mixtures for thioxanthenes. Further electrophoretic parameters were optimized, such as the concentration of the electrolytes, the addition of SDS, the kind of electrolytes and the voltage. Distinct differences in selectivities were found between the derivatives with thioxanthene and dibenzo[b,e]oxepin ring system, respectively. Further, the different basic side chain was responsible for the different selectivity at higher pH* values. In contrast, the substitution at position 2 of the thioxanthenes played a secondary role. Based on the studies of single parameters a method for a simultaneous separation of the four pairs of isomers within 13 min was developed.

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On the Acidity of the Hydroxyl Groups in Calix[4]arenes and the Dissociation-dependent Conformational Change

Cited by 47 publications

References 5 publications

p-Sulfonic acid calix[n]arenes: the most active and water tolerant organocatalysts in esterification reactions

p-Sulfonic acid calix[n]arenes: the most active and water tolerant organocatalysts in esterification reactions

Complexation of basic amino acids by water-soluble calixarene sulphonates as a study of the possiblemechanisms of recognition of calixarene sulphonates by proteins

Separation of (Z)‐ and (E)‐isomers of thioxanthene and dibenz[b,e]oxepin derivatives with calixarenes and resorcinarenes as additives in nonaqueous capillary electrophoresis

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