Question

why is propen-1-amine less basic that propanamine?

Answer 1

Hi.
First of all the basicity of both the mentioned compounds is due to the lone pair present on the nitrogen atom of the amino group. Also whichever nitrogen atom has "greater electron density will be more basic."
Now the reason :-
in propen-1-amine the nitrogen atom is attached to SP2 hybridised carbon which is more electron withdrawing as compared to sp3 carbon of propanamine. Therefore it is less basic due to electron withdrawing nature of sp2 hybridized carbon.

:))