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Updated: Jan 17, 2026

Sulfate Separation by Selective Crystallization with a Bis-iminoguanidinium Ligand

Sulfate Separation by Selective Crystallization with a Bis-iminoguanidinium Ligand

Published on: September 8, 2016

水性硫酸塩に対する高親和性を持つピリジンおよびN-ピリジニウム官能化大環状スクアロアミドアニオン受容体

Thomas M Salmon^1,2, Ena T Luis^1,2, Stephen M Butler^1,2

¹School of Chemistry, The University of Sydney, NSW, Australia.

Chemistry, an Asian journal

|January 14, 2026

Abstract:

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.

キーワード:

アニオン受容体大環状化合物分子認識超分子化学

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Basicity of Heterocyclic Aromatic Amines

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Heterocyclic amines, where the N atom is a part of an alicyclic system, are similar in basicity to alkylamines. Interestingly, the heterocyclic amine having a nitrogen atom as part of an aromatic ring has much less basicity than its corresponding alicyclic counterpart. For this reason, as presented in Figure 1, piperidine (pKb = 2.8) is significantly more basic than pyridine (pKb = 8.8).

Diazonium Group Substitution with Halogens and Cyanide: Sandmeyer and Schiemann Reactions

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Arenediazonium substitution reactions occur when the diazonium group is substituted by various functional groups such as halides, hydroxyl, nitrile, etc. For instance, arenediazonium salts react with copper(I) salts of chloride, bromide, or cyanide to form corresponding aryl chlorides, bromides, and nitriles. These reactions are named Sandmeyer reactions. Although the mechanism of this reaction is complicated, as illustrated in Figure 1, they are believed to progress via an aryl copper...

Diazonium Group Substitution: –OH and –H

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Nitrous acid, a weak acid, is prepared in situ via the reaction of sodium nitrite with a strong acid under cold conditions. This nitrous acid prepared in situ reacts with primary arylamines to form arenediazonium salts. Such reactions are known as diazotization reactions. As shown in Figure 1, the formation of arenediazonium salts begins with the decomposition of nitrous acid in an acidic solution to give nitrosonium ions.

Ion Exchange

Ion Exchange

Ion exchange chromatography separates charged molecules from a solution by reversibly exchanging them with mobile, or 'active', ions associated with the oppositely charged stationary phase. This method can be used to separate ions, soften and deionize water, and purify solutions. The polymers comprising the ion-exchange column are high-molecular-weight and chemically stable polymers, crosslinked to be porous and essentially insoluble. They are also functionalized with either acidic or...

Preparation and Reactions of Sulfides

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Sulfides are the sulfur analog of ethers, just as thiols are the sulfur analog of alcohol. Like ethers, sulfides also consist of two hydrocarbon groups bonded to the central sulfur atom. Depending upon the type of groups present, sulfides can be symmetrical or asymmetrical. Symmetrical sulfides can be prepared via an SN2 reaction between 2 equivalents of an alkyl halide and one equivalent of sodium sulfide.

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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.