title: Deprotonation of calixarenes in acetonitrile.
abstract: [Structure: see text]. The pKa values for calixarenes in MeCN have been determined by selective titration with bases using a spectroscopic method. These values are as follows: calix[4]arene pKa(1) = 19.06 +/- 0.22, pKa(2) > 33; calix[6]arene pKa(1) = 15.59 +/- 0.06, pKa(2) = 23.85 +/- 0.35, pKa(3) > 33; calix[8]arene pKa(1) = 17.20 +/- 0.20, pKa(2) = 20.32 +/- 0.31, pKa(3) > 33. The trends in acidity are rationalized using structures generated by a DFT model. For mono-deprotonation, the degree and nature of hydrogen bonding in the anion is the dominant factor; for di-deprotonation, spatial separation of the anionic charges becomes important.
authors.affiliation: Chemistry, SBMS, University of Surrey, Guildford GU2 7XH, UK. i.cunningham@surrey.ac.uk
authors.forename: Ian D
authors.initials: ID
authors.lastname: Cunningham
authors.forename: Marc
authors.initials: M
authors.lastname: Woolfall