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Contributing structures of the carbonate ion. In chemistry, resonance, also called mesomerism, is a way of describing bonding in certain molecules or polyatomic ions by the combination of several contributing structures (or forms, [1] also variously known as resonance structures or canonical structures) into a resonance hybrid (or hybrid structure) in valence bond theory.
In chemistry, the mesomeric effect (or resonance effect) is a property of substituents or functional groups in a chemical compound.It is defined as the polarity produced in the molecule by the interaction of two pi bonds or between a pi bond and lone pair of electrons present on an adjacent atom. [1]
The two dominant resonance forms of the phosphaethynolate anion localise negative charge on either the phosphorus or oxygen atoms meaning both are sites of nucleophilicity. [11] The same applies for the cyanate anion hence why PCO is observed to have similar pseudo-halogenic behaviour. [3] [12]
Expressing resonance when drawing Lewis structures may be done either by drawing each of the possible resonance forms and placing double-headed arrows between them or by using dashed lines to represent the partial bonds (although the latter is a good representation of the resonance hybrid which is not, formally speaking, a Lewis structure).
The deprotonated conjugate base is the ascorbate anion, which is stabilized by electron delocalization that results from resonance between two forms: For this reason, ascorbic acid is much more acidic than would be expected if the compound contained only isolated hydroxyl groups.
Resonance is largely prevented in the very strained quinuclidone. In their IR spectra, amides exhibit a moderately intense ν CO band near 1650 cm −1. The energy of this band is about 60 cm-1 lower than for the ν CO of esters and ketones. This difference reflects the contribution of the zwitterionic resonance structure.
Oxocarbenium and iminium ions have important secondary canonical forms (resonance structures) in which carbon bears a positive charge. As such, they are carbocations according to the IUPAC definition although some chemists do not regard them to be "true" carbocations, as their most important resonance contributors carry the formal positive ...
Compounds that contain the cyanate functional group, −O−C≡N, are known as cyanates or cyanate esters. Aryl cyanates such are phenyl cyanate, C 6 H 5 OCN can be formed by a reaction of phenol with cyanogen chloride, ClCN, in the presence of a base. Organic compounds that contain the isocyanate functional group −N=C=O are known as ...