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Issue 6, 2002
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Acid–base properties of sulfur-bridged calix[4]arenes

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Abstract

The acid–base properties of sulfur-bridged calixarenes, thiacalix[4]arenetetrasulfonate (4) and its sulfonyl analogue (5), have been investigated via potentio- and spectrophoto-metric studies, comparing them with the conventional methylene-bridged calix[4]arenetetrasulfonate (3). The titration curves revealed the acidity of the phenolic OH groups in the calix[4]arenes 35 to be in the order: 3 < 45. In particular, the oxidation of the bridging sulfur to sulfone strongly enhanced the acidity of the sulfur-bridged calix[4]arene; the pKa,n values (n = 2–4) of the sulfone-bridged 5 were lower by 7 pK units than those of the sulfide-bridged 4. The effects of the linkage groups on the acidity of the calix[4]arenes are discussed from the structural and electronic viewpoints, such as the macrocyclic ring size, the hydrogen bonding manner, and the resonance of the linkage moiety.

Graphical abstract: Acid–base properties of sulfur-bridged calix[4]arenes

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Article information


Submitted
08 Jan 2002
Accepted
15 Apr 2002
First published
09 May 2002

J. Chem. Soc., Perkin Trans. 2, 2002, 1166-1172
Article type
Paper

Acid–base properties of sulfur-bridged calix[4]arenes

H. Matsumiya, Y. Terazono, N. Iki and S. Miyano, J. Chem. Soc., Perkin Trans. 2, 2002, 1166
DOI: 10.1039/B200228K

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