Related Experiment Video
Updated: Jan 17, 2026

Sulfate Separation by Selective Crystallization with a Bis-iminoguanidinium Ligand
Published on: September 8, 2016
Pyridine and N-Pyridinium Functionalized Macrocyclic Squaramide Anion Receptors with High Affinity for Aqueous
Thomas M Salmon1,2, Ena T Luis1,2, Stephen M Butler1,2
1School of Chemistry, The University of Sydney, NSW, Australia.
None:
Macrocyclic squaramide-containing receptors have previously been shown to bind sulfate with high selectivity and affinity in aqueous-organic mixtures. To increase binding affinity of this class of hydrogen-bonding receptors in pure water, macrocycles in which pyridinium groups have been inserted to provide additional charge-assisted hydrogen-bonding interactions were synthesized and their anion binding evaluated. The inclusion of charge-assisted interactions provides enhanced binding affinity for sulfate in water but concomitantly reduces ability of the receptors to discriminate sulfate from the closely related selenate and leads to unexpected changes in binding stoichiometry.
More Related Videos
10:31Detection and Recovery of Palladium, Gold and Cobalt Metals from the Urban Mine Using Novel Sensors/Adsorbents Designated with Nanoscale Wagon-wheel-shaped Pores
Published on: December 6, 2015
14:11Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach
Published on: June 10, 2021
Related Concept Videos
Basicity of Heterocyclic Aromatic Amines
Diazonium Group Substitution with Halogens and Cyanide: Sandmeyer and Schiemann Reactions
Diazonium Group Substitution: –OH and –H
Ion Exchange
Preparation and Reactions of Sulfides
Acidity of 1-Alkynes
The acidic strength of hydrocarbons follows the order: Alkynes > Alkenes > Alkanes. The strength of an acid is commonly expressed in units of pKa — the lower the pKa, the stronger the acid. Among the hydrocarbons, terminal alkynes have lower pKa values and are, therefore, more acidic. For example, the pKa values for ethane, ethene, and acetylene are 51, 44, and 25, respectively, as shown here.