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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 ]
They are reactants in 1,3-dipolar cycloadditions. [1] [2] 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−b−c −, where a may be a carbon, oxygen or nitrogen, b may be nitrogen or oxygen, and c may be a carbon, oxygen or nitrogen. [3]
However, a few examples exist of a stepwise mechanism for the catalyst-free 1,3-dipolar cycloaddition reactions of thiocarbonyl ylides, [6] and nitrile oxides [7] The generic mechanism of a 1,3-dipolar cycloaddition between a dipole and a dipolarophile to give a five-membered heterocycle, through a six-electron transition state.
In physics, a dipole (from Ancient Greek δίς (dís) 'twice' and πόλος (pólos) 'axis') [1] [2] [3] is an electromagnetic phenomenon which occurs in two ways: An electric dipole deals with the separation of the positive and negative electric charges found in any electromagnetic system. A simple example of this system is a pair of charges ...
Note that the dipole moments drawn in this diagram represent the shift of the valence electrons as the origin of the charge, which is opposite the direction of the actual electric dipole moment. The bond dipole moment [5] uses the idea of electric dipole moment to measure the polarity of a chemical bond within a molecule. It occurs whenever ...
An example of a dipole–dipole interaction can be seen in hydrogen chloride (HCl): the positive end of a polar molecule will attract the negative end of the other molecule and influence its position. Polar molecules have a net attraction between them. Examples of polar molecules include hydrogen chloride (HCl) and chloroform (CHCl 3).
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[2] 1,2-dipolar compounds, such as ylides, are sometimes excluded from the definition. [3] Some zwitterions, such as amino acid zwitterions, are in chemical equilibrium with an uncharged "parent" molecule. Betaines are zwitterions that cannot isomerize to an all-neutral form, such as when the positive charge is located on a quaternary ammonium ...