# Comparison of basic strength of benzylamine and ammonia

According to me, ammonia should be the stronger base for two reasons:

1. $\ce{-C_6H_5}$ group shows $-I$ effect, due to which electron density on $\ce{N}$ atom of benzylamine decreases
2. steric hindrance in benzylamine is more than that in ammonia

But their $\mathrm{pK_b}$ values are: benzylamine: $4.70$ and ammonia : $4.75$. High $\mathrm{pK_b}$ value of ammonia shows that it is actually less basic than benzylamine, contrary to my reasoning. Why is it so?

• See nitrogen inversion $\ce{->}$Wikipedia Feb 8 '18 at 14:38

Benzylamine is $$\ce{C6H5CH2NH2}.$$ Therefore, $$\ce{NH2}$$ group is bonded to $$\ce{C6H5-CH2}$$ unit which has greater +I effect. Therefore, it increases electron density on $$\ce{N}$$ and makes benzylamine more basic.