Question

Its basic strength is ${10}^{10}$ more than 1-dimethyl amino naphthalene due to:

• A. resonance
• B. steric inhibitation of resonance
• C. ortho effect
• D. hyperconjugation

Answer 1

Answer: (B)

steric inhibitation of resonance

For participation in resonance, the $p-orbital$ of $N$ should be perpendicular to the plane of the ring.
Presence of two bulky methyl groups does not allow the $p-orbital$ to get perpendicular to the plane and hence the lone pair of $N$ does not involve in resonance.
This increases the lone pair availability, thus increasing the basic strength.
Hence, $1,8-bis\left(dimethylamino\right)$ napthalene is more basic than $1-dimethylamino$ napthalene due to steric inhibition of resonance.