Ada 2009 #78

[n27s]

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Are carboxylic acids or aromatic acids more acidic? Destroyer says aromatic acids > carboxy acids > alcohols > ketones/aldehydes > alkynes etc.. but number 78 on the ADA 09 exam has the answer as acetic acid (CH3COOH) will be more acidic than a phenol, I am confused now! Is it another ADA error? The 09 is full off it!

 

[njdoc327]

carboxy acids are very acidic. however aromaticity will increase acidity. so in the case of benzoic acid vs acetic acid, benzoic acid is more acidic. however a carboxy acid is more acidic than a phenol regardless of aromaticity. the pka of acetic acid is about 5 and the pka of benzoic acid is 4. and the pka of phenol is around 9-10

 

[n27s]

thanks for clearing that up!