Steric inhibition of resonance

Steric Inhibition of Resonance

       Resonance inhibition effect on 

1) Physical properties

2) Acidity & basicity &

3) Reactivity of the compounds

 1) Physical properties & steric inhibition of the resonance: 

i) Bond length & bond strength:

       Resonance increases bond length with double bond & decreases with single bond.

  

 C一N bond is more because both type of bond single & double bond involved in resonance. But in following structure,

t-Bu group inhibits the resonance hence C一N bond is only single bond.

2) Dipole moments: 

        Steric inhibition reduces the dipole moments because their dipole distance becomes less in aromatic compounds  

 

 Distance of two poles is large.

 Distance of two poles is less.