D

Dimer

2A ⇌ A₂ (e.g., 2NO₂ ⇌ N₂O₄)
Quick Reference
Formula / Notation2A ⇌ A₂ (e.g., 2NO₂ ⇌ N₂O₄)
Also Known AsMolecular dimer, homodimer, dimerisation product, bimolecular association

What is Dimer?

A molecule formed by the combination of two identical or similar monomer units. Dimers can be held together by covalent bonds or weaker intermolecular forces. For example, acetic acid forms dimers in the gas phase through hydrogen bonding.

Formula & Notation

2A ⇌ A₂ (e.g., 2NO₂ ⇌ N₂O₄)

Other Names / Synonyms: Molecular dimer, homodimer, dimerisation product, bimolecular association

Properties & Characteristics

A dimer is a molecule or complex formed by the association or combination of two identical monomeric units. Dimers can be covalent (acetic acid dimer via hydrogen bonding, diborane B₂H₆), non-covalent (protein homodimers via hydrophobic interactions), or ionic. Protein dimers often exhibit allosteric regulation. The dimerisation equilibrium is characterised by a dimerisation constant Kd.

Uses & Applications

Dimers are important in catalysis (many enzymes are dimers), polymer chemistry (dimerisation as a side reaction), atmospheric chemistry (dinitrogen tetroxide N₂O₄ ⇌ 2NO₂ equilibrium important in rocket propellants), and in materials science (dimer formation in liquid crystals and self-assembled monolayers).

Safety Information

Some dimers are more hazardous than the monomer: dinitrogen tetroxide (N₂O₄) is a toxic oxidiser used as rocket fuel. Cyclopentadiene dimerises to dicyclopentadiene; the monomer can be obtained by thermal cracking, but it is flammable and irritant.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Dimer
Formula 2A ⇌ A₂ (e.g., 2NO₂ ⇌ N₂O₄)
Synonyms Molecular dimer, homodimer, dimerisation product, bimolecular association

Frequently Asked Questions

A molecule formed by the combination of two identical or similar monomer units. Dimers can be held together by covalent bonds or weaker intermolecular forces. For example, acetic acid forms dimers in the gas phase through hydrogen bonding.

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