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.
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.
Dipolar compounds can be represented by a
resonance structure. Contributing structures containing charged atoms are denoted as
zwitterions.
[{{cite journal, last1=MacHiguchi, first1=Takahisa, last2=Okamoto, first2=Junko, last3=Takachi, first3=Junpei, last4=Hasegawa, first4=Toshio, last5=Yamabe, first5=Shinichi, last6=Minato, first6=Tsutomu, title=Exclusive Formation of α-Methyleneoxetanes in Ketene−Alkene Cycloadditions. Evidence for Intervention of Both an α-Methyleneoxetane and the Subsequent 1,4-Zwitterion, journal=Journal of the American Chemical Society, volume=125, issue=47, pages=14446–8, year=2003, pmid=14624592, doi=10.1021/ja030191g]
[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.
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.
They are reactants in
1,3-dipolar cycloadditions.
*Also 1,4-dipolars,
[ 1,5-dipolars, and so on exist.
]
Examples
File:Triphenyl phosphonium ylide.svg, Phosphonium ylide
The Wittig reaction or Wittig olefination is a chemical reaction of an aldehyde or ketone with a triphenyl phosphonium ylide called a Wittig reagent. Wittig reactions are most commonly used to convert aldehydes and ketones to alkenes. Most of ...
File:Diazomethane.svg, Diazo
The diazo group is an organic moiety consisting of two linked nitrogen atoms ( azo) at the terminal position. Overall charge neutral organic compounds containing the diazo group bound to a carbon atom are called diazo compounds or diazoalkanes ...
methane
File:Carbonyl oxide (Criegee zwitterion).svg, Carbonyl oxide
See also
* Zwitterion
* Ylide
*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 st ...
* 1,3-Dipolar cycloaddition
* Betaine
References
Organic chemistry