Resonance contributors

[NA19]

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Which of the following is an appropriate resonance form of the conjugate base of p-aminobenzoic acid?

I'm struggling with how to approach resonance questions. If someone could help, that would be great!

 

[Temperature101]

Which of the following is an appropriate resonance form of the conjugate base of p-aminobenzoic acid?

I'm struggling with how to approach resonance questions. If someone could help, that would be great!

C should be the answer...Look at the charges...

 

[FeinMS]

That's a gross looking question.
A. Eliminated because carboxyl carbon is pentavalent (the worst thing you can draw in ochem)
B. Eliminated because carboxyl carbon has 3 bonds without + formal charge.
C. Looks ok without any violation of bondings and formal charge
D. Eliminated because carbon connected to the carboxyl carbon has 4 bonds with a formal charge
E. same reason as D

 

[NA19]

So can you just approach resonance questions by figuring out how many bonds the carbons have and what formal charges they have? Are there any other strategies people recommend?

 

[monkeyvokes]

So can you just approach resonance questions by figuring out how many bonds the carbons have and what formal charges they have? Are there any other strategies people recommend?

the ones with nitrogen in the ring are wrong
the net charge should be -1, equal to the net charge of p aminobenzoate (the conjugate base)

these two rules alone rule out everything but C