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.
![{\displaystyle {\ce {[R-{\overset {\oplus }{N}}{\equiv }{\overset {\ominus }{C}}{:}<->R-{\ddot {N}}=C{:}]}}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/5755177ecf83528cc710550d28d4727f06d6f8f0)
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
edit- 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
editReferences
edit- ^ a b IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "dipolar compounds". doi:10.1351/goldbook.D01753
- ^ 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
- ^ 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
- ^ a b 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.
- ^ Preferred IUPAC Names: "CHAPTER 7: RADICALS, IONS, AND RELATED SPECIES", September 2004, pp. 56-70
- ^ Rolf Huisgen (IUPAC): Cycloaddition mechanism and the solvent dependence of rate; Pure Appl. Chem.; 1980, Vol.52, pp.2283—2302.