1,3-dipole

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. They are reactants in 1,3-dipolar cycloadditions.

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\sb\sc-, where a may be a carbon, oxygen or nitrogen, b may be nitrogen or oxygen, and c may be a carbon, oxygen or nitrogen. 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)
 * Nitrile oxides (RCN\sO)
 * Nitrous oxide (N2O)
 * Nitrones (R2CN(R)O)
 * Some imines:
 * Azomethine imine
 * Nitrilimines (RCN\sNR, analogous to nitrile oxide)
 * Carbonyl imines
 * Some ylides
 * Azomethine ylide
 * Nitrile ylide (RCNCR'2)
 * Carbonyl ylide
 * Thiosulfines (R2CSS)