Very simple resonance question

[TheRelevant]

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Hey guys,

Hope the MCAT studying is going well. Just wanted to confirm that this mechanism is the reason why the alkene is electron-withdrawing and therefore decreases the nitrogen's basicity? Thank you!

 

[JMMTB]

Yes that is absolutely correct. The nitrogen is sp2 hybridized thus the lone pair is tied up in the pi system. This makes it less available to grab a proton and act as a base. An sp3 Nitrogen is thus more basic because the lone pair can easily grab a proton.

Nice job!

 

[TheRelevant]

Thanks for your reply and encouragment 🙂

The resonance structure on the right is a fairly small contributor, given that the negative charge is on the less electronegative atom. Do we still consider the nitrogen sp2 hybridized despite the relatively small contribution of the resonance contributor that causes nitrogen's sp2 hybridization? Thanks again!

 

[JMMTB]

Yes the resonance structure on the right is the minor contributor but we have to remember that in reality the structure is a hybrid of the two. Our use of lines and dots can only show when electrons are temporarily. It is this hybrid that explains why the nitrogen is sp2.