Which acid is the strongest?

[sopliim]

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Which acid is more stronger?

NO2CH2COOH vs benzoic acid.

Answer is NO2CH2COOH..
Following by cardio rule, benzoic zcid is more stronger acid because of resonance priority.
Anyone can explain??

 

[DAT Destroyer]

Which acid is more stronger?

NO2CH2COOH vs benzoic acid.

Answer is NO2CH2COOH..
Following by cardio rule, benzoic zcid is more stronger acid because of resonance priority.
Anyone can explain??

This is Not even close,,,,,,The nitroacetic acid has a pKa of about 1.7,,,,,,Benzoic Acid is about 4.2.......the nitroacetic acid has an anion that is well stabilized by resonance,,,,as well as by the Inductive Effect due to the NO2 group. Oxygen carries a negative charge quite well.....and this is borne out in the many resonance forms that can be drawn for this anion.

Believe it or not......Benzoic acid is NOT that much more acidic than an aliphatic carboxy acid such as acetic or propanoic acid !!!The negative charge on the carboxylate ion is shared by the two carboxylate oxygens and is NOT effectively delocalized by the aromatic ring. Having resonance forms in which carbon bears the negative charge contributes only slightly.

As a general rule.....DO NOT bet against a NITRO group or a Cyano group when it comes to acidity ....as these groups stabilize the anion by resonance AND induction quite well.

I hope this helps.....

Dr. Jim Romano

 

[whoaarr]

Which acid is more stronger?

NO2CH2COOH vs benzoic acid.

Answer is NO2CH2COOH..
Following by cardio rule, benzoic zcid is more stronger acid because of resonance priority.
Anyone can explain??

Wouldn't the A have priority over R in CARDIO? Nitrogen is more electronegative than carbon. Maybe I'm oversimplifying things..

 

[DAT Destroyer]

Wouldn't the A have priority over R in CARDIO? Nitrogen is more electronegative than carbon. Maybe I'm oversimplifying things..

Yes.....oversimplifying indeed. LOL......CARDIO is a very general rule......from the Klein book.

As you can see by the pKa values,,,,,,Benzoic acid is not even close. You seem a bit confused. As I stated above......In Benzoic acid,,,,,Oxygen has the negative charges .....the most significant resonance forms are from these canonicals. In the nitro compound,,,,,,Oxygen carries the negative charges on the carboxylate BUT......Nitro also allows for Oxygen to bear the negative charges...and these resonance forms are quite significant.

Consult a text to examine the structure of a Nitro group.

Dr. Romano