1,3-dipole

From top to bottom, azides, nitrones, and nitro compounds are examples of 1,3-dipoles.

In organic chemistry, a 1,3-dipolar compound or 1,3-dipole is a dipolar compound with delocalized electrons and a separation of charge over three atoms, as follows: the dipole has at least one resonance structure with positive and negative charges having a 1,3 relationship which can generally be denoted as ⁺a−b−c⁻, where a may be a carbon, oxygen or nitrogen, b may be nitrogen or oxygen, and c may be a carbon, oxygen or nitrogen. ^[1]

A demonstration that how some well known 1,3-dipoles like ozone, nitro compounds and azides can be shown to have a resonance structure having 1,3 relationship between positive and negative formal charges

They are reactants in 1,3-dipolar cycloadditions. ^{[2] [3]}

Known 1,3-dipoles are:

• Azides (RN₃)
• Ozone (O₃)
• Nitro compounds (RNO₂)
• Diazo compounds (R₂CN₂)
• Some oxides
  • Azoxide compounds (RN(O)NR)
  • Carbonyl oxides (Criegee zwitterions) ^{[4] [5]}
  • Nitrile oxides (RCN−O)
  • Nitrous oxide (N₂O)
  • Nitrones (R₂CN(R)O)

Carbonyl oxide

• Some imines:
  • Azomethine imine
  • Nitrilimines (RCN−NR, analogous to nitrile oxide)
  • Carbonyl imines
• Some ylides
  • Azomethine ylide
  • Nitrile ylide (RCNCR'₂)
  • Carbonyl ylide
  • Thiosulfines (R₂CSS)

References

1. Jagadamba, Singh (2009). Photochemistry and Pericyclic Reactions. New Academic Science. p. 100. ISBN   978-1906574161.
2. Francis A. Carey, Richard J. Sundberg (2007). "Part A: Structure and mechanisms". Advanced Organic Chemistry (5, illustrated ed.). Springer. p. 874. ISBN   978-0-387-44897-8.
3. IUPAC Gold Book dipolar compounds
4. https://www.organic-chemistry.org/namedreactions/ozonolysis-criegee-mechanism.shtm Ozonolysis mechanism on Organic Chemistry Portal site
5. Li, Jie Jack: Criegee mechanism of ozonolysis Book: Name Reactions. 2006, 173-174, doi : 10.1007/3-540-30031-7_77