Destroyer 2015 orgo problem 31

[maiyaa]

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[FeralisExtremum]

This isn't so much about electron donating/withdrawing (like ortho/meta/para stuff) as it is simply resonance and other CARDIO factors that affect the strength of a base.

The most basic one is going to be the one that is least stable. We also note that the electron pair on the Nitrogen atom is most likely what we're focusing on in terms of where the base will attack from. So looking at our choices, which ones have stabilization going for them, therefore being relatively weaker bases? If you number them 1 - 5 starting from the left: 2, 3, and 5 all have resonance stabilization from the attached benzene ring. We can instantly rule them out as they are less basic.

That leaves 1 and 4. What other factors in CARDIO (Chad's mnemomic from his first Orgo lecture) are differentiating the two? The orbitals of the Nitrogen atom. Since choice 4 is sp2 hybridized, it stabilizes the electron pair on that atom more so than the sp3 hybridized Nitrogen atom in choice 1.

Choice 1 is left as the least stable (and most basic) as a result.

 

[maiyaa]

Thanks again! 🙂

 

[DAT Destroyer]

Hello!

Can someone explain to me what's electron withdrawing and what is electron donating in the answer choices?

I'm comparing the solution in the back to chads videos.

The solution says the first one is more basic. View attachment 188272

Here is a simple way to do this problem. The first compound is more basic because the electrons are totally LOCALIZED on the nitrogen atom. The other choices have resonance and electron withdrawing groups removing electron density from the nitrogen making it less basic. As a general rule an SP3 nitrogen will be more basic than an SP2 nitrogen since the electrons are more loosely held and can be shared with a proton.

Hope this helps..

 

[maiyaa]

Thank you.