- Conjugate acids of both molecules have the same number of stable resonance structures. So no conclusion from here.
- Conjugate acid of 2-imidazoline will have negative inductive on the lone pair donating nitrogen by the other nitrogen atom. Since this effect is absent in acetamidine, acetamidine should be a stronger base.
Is the above approach right? Can ring strain affect the basic strength of 2-imidazoline in any way? Should I consider any other factor too to make the right comparison of the basic strength of the above two molecules?