Determination of the acid dissociation constants of the p-sulphonato-calix[4]arene

Subject Areas : Journal of Nanoanalysis

Monireh  Hajmalek ¹ (Department of Chemistry, Islamic Azad University, Science and Research Branch, Tehran, Iran)
Mohammad Sajjad  Khalili ² (Department of Chemistry, Faculty of Science and Engineering, Islamic Azad University, Saveh Branch, Saveh, Iran)
Karim  Zare ³ (Department of Chemistry, Islamic Azad University, Science and Research Branch, Tehran, Iran)
Omid  Zabihi ⁴ (Department of Chemistry, Islamic Azad University, Science and Research Branch, Tehran, Iran)

Received: 2017-05-31 Accepted : 2017-05-31 Published : 2014-04-01

Keywords: p-sulfonatocalix[4]arene, acid–base properties, acid dissociation constant,

Abstract :

The acid dissociation constants of the hydroxyl groups in 25, 26, 27, 28-tetrahydroxy-5, 11, 17, 23-tetrasulphonic-calix[4]arene (SC4) were determined at 25οC by a combination of potentiometric and spectrophotometric titration method. The first and second acid dissociation constants (pKa1, pKa2) were found to be 3.19 and 12.1, which demonstrated pKa shift due to intramolecular hydrogen bonding interactions among hydroxyl groups in SC4.