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Related Concept Videos

Ionic Association01:28

Ionic Association

199
The ionic association is the association of oppositely charged ions in an electrolyte solution to form ion pairs. Bjerrum defined ion pairs as two oppositely charged ions whose electrostatic attraction exceeds the thermal energy of the system, typically expressed as 2kT. Electrostatic attraction depends on ionic charge, separation distance, and the dielectric constant of the medium. Thermal energy, represented by kT, reflects the tendency of ions to move independently due to molecular motion.
199
Ions as Acids and Bases02:54

Ions as Acids and Bases

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Salts with Acidic Ions
Salts are ionic compounds composed of cations and anions, either of which may be capable of undergoing an acid or base ionization reaction with water. Aqueous salt solutions, therefore, may be acidic, basic, or neutral, depending on the relative acid-base strengths of the salt’s constituent ions. For example, dissolving the ammonium chloride in water results in its dissociation, as described by the equation:
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Ionic Crystal Structures02:42

Ionic Crystal Structures

21.6K
Ionic crystals consist of two or more different kinds of ions that usually have different sizes. The packing of these ions into a crystal structure is more complex than the packing of metal atoms that are the same size.
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...
21.6K
Basicity of Heterocyclic Aromatic Amines01:25

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).
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Formation of Complex Ions03:45

Formation of Complex Ions

26.9K
A type of Lewis acid-base chemistry involves the formation of a complex ion (or a coordination complex) comprising a central atom, typically a transition metal cation, surrounded by ions or molecules called ligands. These ligands can be neutral molecules like H2O or NH3, or ions such as CN− or OH−. Often, the ligands act as Lewis bases, donating a pair of electrons to the central atom. These types of Lewis acid-base reactions are examples of a broad subdiscipline called coordination...
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Determining the pH of Salt Solutions04:08

Determining the pH of Salt Solutions

50.7K
The pH of a salt solution is determined by its component anions and cations. Salts that contain pH-neutral anions and the hydronium ion-producing cations form a solution with a pH less than 7. For example, in ammonium nitrate (NH4NO3) solution, NO3− ions do not react with water whereas NH4+ ions produce the hydronium ions resulting in the acidic solution. In contrast, salts that contain pH-neutral cations and the hydroxide ion-producing anions form a solution with a pH greater than 7.
50.7K

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Related Experiment Video

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Ion Mobility-Mass Spectrometry Techniques for Determining the Structure and Mechanisms of Metal Ion Recognition and Redox Activity of Metal Binding Oligopeptides
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Ion Mobility-Mass Spectrometry Techniques for Determining the Structure and Mechanisms of Metal Ion Recognition and Redox Activity of Metal Binding Oligopeptides

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Imidazolium salt ion pairs in solution.

Hubert K Stassen1, Ralf Ludwig2,3, Alexander Wulf2

  • 1Institute of Chemistry, UFRGS, Av. Bento Gonçalves, 9500 Porto Alegre 91501-970 RS (Brazil).

Chemistry (Weinheim an Der Bergstrasse, Germany)
|April 3, 2015
PubMed
Summary

Imidazolium ionic liquids form contact ion pairs and larger aggregates in solution. Their stability and reactivity depend on solvent, concentration, and ion structure, influencing their behavior in various applications.

Keywords:
conductivityimidazolium saltsion pairsionic liquidssolutions

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Area of Science:

  • Physical Chemistry
  • Supramolecular Chemistry
  • Materials Science

Background:

  • Non-protic imidazolium ionic liquids (ILs) are versatile solvents and electrolytes.
  • Understanding ion aggregation is crucial for predicting IL behavior in solution.
  • Previous studies have explored IL structure-property relationships, but aggregation dynamics require further clarification.

Purpose of the Study:

  • To conceptualize the formation, stabilization, and reactivity of contact ion pairs in imidazolium ILs.
  • To investigate the influence of solvent, concentration, and ion structure on IL aggregation.
  • To differentiate between contact ion pairs and solvent-separated ions in IL solutions.

Main Methods:

  • Analysis of experimental data including electric conductivity, NMR, ESI-MS, and IR spectroscopy.
  • Inclusion of theoretical calculations from the last decade.
  • Focus on non-protic imidazolium-based ionic liquids.

Main Results:

  • Experimental and theoretical data confirm the formation of contact ion pairs in IL solutions.
  • Larger ionic and neutral aggregates are observed even in high dielectric constant solvents.
  • Aggregate formation is favored by higher salt concentrations, low dielectric constants, shorter N-alkyl chains, and low-coordination anions.
  • Stability and reactivity are influenced by anion nature, imidazolium substituents, and charge-transfer complex formation.

Conclusions:

  • Imidazolium ILs exist as contact ion pairs and larger aggregates in solution.
  • Ion aggregation is a significant factor affecting IL properties and reactivity.
  • Some ILs exhibit reactivity primarily as contact ion pairs, deviating from solvent-separated ion behavior.