Question

Which is the stronger base CH3-CH2-NH2 or CH2=CH-NH2? I know it has something to do with resonance but I dont quite know how. How do I know which is engaged in resonance?

Answer 1

The lewis bases are the substances that donates its lone pair of electrons to the other compounds in the reaction.

In both these compounds , amine group is present that has an available lone pair on the Nitrogen atom.

The lone pair of the CH2=CH-NH2 , is in the conjugation with the double bond , so it is less available for the donation , whereas the lone pair of nitrogen atom in CH3-CH2-NH2 is freely available.

So the later donates its electron pair more easily , and hence behaves as a stronger base.

To know if there is resonance or not , look for alternating double and single bonds like this : - = -

or you can look for electron single bond and then double bond , or look for positive charge single bond and then double bond.

Hope this helps !!