dipolar compounds

Electrically neutral molecules carrying a positive and a negative charge in one of their major canonical descriptions. In most dipolar compounds the charges are delocalized; however the term is also applied to species where this is not the case. 1,2-Dipolar compounds have the opposite charges on adjacent atoms. The term 1,3-dipolar compounds is used for those in which a significant canonical resonance form can be represented by a separation of charge over three atoms (in connection with 1,3-dipolar cycloadditions). Subclasses of 1,3-dipolar compounds include:

1. Allyl type X=Y⁺–Z⁻X⁻–Y⁺=ZX⁺–Y–Z⁻X⁻=Y–Z⁺ (X, Z = C, N, or O; Y = N or O)
   See: azo imides, azomethine imides, azomethine ylides, azoxy compounds, carbonyl imides, carbonyl oxides, carbonyl ylides, nitrones, nitro compounds
2. Propargyl type X≡N⁺–Z⁻X⁻=N⁺=ZX⁻=N–Z⁺X–N=Z (X = C or O, Z = C, N, or O)
   See: nitrile imides, nitrile oxides, nitrile ylides, nitrilium betaines, azides, diazo compounds
3. Carbene type X:–C=ZX⁺=C–Z⁻ (X = C or N; Z = C, N, or O)
   See: acyl carbenes, imidoyl carbenes, vinyl carbenes
   See: betaines
   Source:
   PAC, 1995, 67, 1307 (Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1333