Interpret the following values of $pK_a$ (the larger the $pK_a$ is, the stronger the base)
- In e), the $-I$ of oxygen effect and the $-M$ effect "suck" the doublet N which becomes less available to fix $H^+$
- Ammonia d) does not benefit from $+I$ effects that would make the $N$ doublet more available.
- The secondary amine a) is more basic than the primary amine b) because of two $+I$ effects on $N$ (on both sides of the ring)
- In general, the tertiary amines are less basic than primary amines because of steric hindrance. Here this space is reduced due to the narrow cycle which would explain the equal basicities of b) and c).
