Acidity Question

[DrTacoElf]

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Rank the following from LEAST acidic to MOST acidic

Phenol
methanoic acid
ethanoic acid
ethanol

Clearly ethanol is least acidic, but after that it becomes less clear to me. In phenol resonance is a pretty big player but generally carboxylic acids are more acidic. So here is what i reason (please tell me if this is correct)

From LEAST acidic to MOST acidic

ethanol, phenol, ethanoic acid, methanoic acid

I assumed that methanoic acid is more acidic than ethanoic acid b/c with ethanoic acid you have an alkyl group (CH3) which is donating electrons thus the labile proton is less likely to be removed?


ANy input guys?

 

[Cowboy DO]

Acoording to this site:

http://people.ouc.bc.ca/woodcock/molecule/modelfiles/Acids_(organic).htm

methanoic acid: ~pKa 3.75
ethanoic acid: ~pKa 4.75

So methanoic acid is stronger, and your logic in deducing that seems correct to me.

 

[ItsGavinC]

Dr TacoElf, good question, but I hope you aren't using these questions to gauge your level of preparation for the DAT. The DAT would ask, which is the strongest acid: HCl, water, bubblegum, or asparagus? Seriously.

You'll do fine!