Resonance structure:
Resonance structures are sets of Lewis structures that describe the delocalization of electrons in a polyatomic ion or a molecule.
a) Resonance structures for
C6H5OH
The lone pair of electron starts shifting to oxygen - carbon bond and form a double bond character and
π electron of
C−C bond shift to next
C−C single bond.
![](https://df0b18phdhzpx.cloudfront.net/ckeditor_assets/pictures/1643939/original_Web_capture_25-4-2022_17653_.jpeg)
b) Resonance structures for
C6H5NO2
Here the electrons of
N−O bonds shift to oxygen atom (more electronegative) and then the
π electron of carbon-carbon double bonds starts delocalising towards the
N atom.
![](https://df0b18phdhzpx.cloudfront.net/ckeditor_assets/pictures/1643952/original_Web_capture_25-4-2022_17921_.jpeg)
c) Resonance structures for
CH3CH=CH−CHO
Here the
π electrons of
C−O bond shifts to oxygen atom (more electronegative) and then the
π electron of carbon-carbon double bonds starts shifting towards the next
C−C bond, introducing a partial double bond character.
![](https://df0b18phdhzpx.cloudfront.net/ckeditor_assets/pictures/1643965/original_Web_capture_25-4-2022_171120_.jpeg)
d) Resonance structures for
C6H5−CHO
Here the
π electron of carbon-oxygen double bond starts shifting towards the electronegative oxygen atom and the
π-electrons of
C−C double bonds shifting towards carbonyl group (as shown in figure).
![](https://df0b18phdhzpx.cloudfront.net/ckeditor_assets/pictures/1643974/original_Web_capture_25-4-2022_171257_.jpeg)
e) Resonance structures for
C6H5−+CH2
The
π - electrons of
C−C double bond shift towards the bond to minimise the deficiency of electron density and the rest of the
π - electrons follow the same process
![](https://df0b18phdhzpx.cloudfront.net/ckeditor_assets/pictures/1643978/original_Web_capture_25-4-2022_171514_.jpeg)
f) Resonance structure for
CH3CH=CH+CH2
The
π-electrons of
C−C double bond shift towards the
C−C+ bond to minimise the deficiency of electron density at
CH+2. So, in this way only one resonant is possible.
![](https://df0b18phdhzpx.cloudfront.net/ckeditor_assets/pictures/1643985/original_Web_capture_25-4-2022_171750_.jpeg)