Question

ethanoic acid is a weaker acid than benzoic acid . why

Answer 1

Stronger acids have lower pKa value. The ethanoic acid (pKa = 4.76) is weaker acid than benzoic acid (pKa = 4.19 ).

Explanation

Electron withdrawing groups increase the acidity of carboxylic acids by stabilising the conjugate base through delocalisation of the negative charge by inductive and/or resonance effects. Due to the presence of benzene ring in benzoic acid, delocalisation of electron makes it more acidic than ethanoic acid but such stabilization is not present in ethanoic acid.

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