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 c****an generally be denoted as +a\sb\sc-, where a may be a c****arbon, oxygen or nitrogen, b may be nitrogen or oxygen, and c may be a c****arbon, oxygen or nitrogen. Known 1,3-dipoles are: