Dipolar compound

In organic chemistry, a dipolar compound or simply dipole is an electrically neutral molecule carrying a positive and a negative charge in at least one canonical description. In most dipolar compounds the charges are delocalized.[1] Unlike salts, dipolar compounds have charges on separate atoms, not on positive and negative ions that make up the compound. Dipolar compounds exhibit a dipole moment.

Example of a dipolar compound, represented by a resonance structure (isocyanide)

Dipolar compounds can be represented by a resonance structure. Contributing structures containing charged atoms are denoted as zwitterions. [2] [3] [4] [5] [6] Some dipolar compounds can have an uncharged canonical form.

Types of dipolar compounds
  • 1,2-dipolar compounds have the opposite charges on adjacent atoms.
  • 1,3-dipolar compounds have the charges separated over three atoms.[1] They are reactants in 1,3-dipolar cycloadditions.
  • Also 1,4-dipolars,[4] 1,5-dipolars, and so on exist.

Examples
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See also

References
  1. IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "dipolar compounds". doi:10.1351/goldbook.D01753
  2. Braida et al.: A clear correlation between the diradical character of 1,3-dipoles and their reactivity toward ethylene or acetylene.; J. Am. Chem. Soc.; 2010 Jun 9;132(22):7631-7
  3. Hartmann and Heuschmann: Isolation of a Zwitterion in a Diels–Alder Reaction with Inverse Electron Demand; Angewandte Chemie; september 1989; Volume 28, Issue 9, pages 1267–1268
  4. MacHiguchi, Takahisa; Okamoto, Junko; Takachi, Junpei; Hasegawa, Toshio; Yamabe, Shinichi; Minato, Tsutomu (2003). "Exclusive Formation of α-Methyleneoxetanes in Ketene−Alkene Cycloadditions. Evidence for Intervention of Both an α-Methyleneoxetane and the Subsequent 1,4-Zwitterion". Journal of the American Chemical Society. 125 (47): 14446–8. doi:10.1021/ja030191g. PMID 14624592.
  5. IUPAC: Preferred IUPAC Names; Chapter 7, September 2004, pp. 56-70
  6. Rolf Huisgen (IUPAC): Cycloaddition mechanism and the solvent dependence of rate; Pure Appl. Chem.; 1980, Vol.52, pp.2283—2302.
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