Substituents affect carboxylic acid acidity by influencing the stability of the conjugate base. Electron-withdrawing groups increase acidity by stabilizing the conjugate base through inductive and/or resonance effects, while electron-donating groups decrease acidity by destabilizing the conjugate base.
How do substituents influence the acidity of carboxylic acids, and what is the impact of electron-withdrawing groups versus electron-donating groups on the stability of the conjugate base?
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Substituents in carboxylic acids can significantly affect acidity. Electron-withdrawing groups (EWG) enhance acidity by stabilizing the conjugate base through resonance and inductive effects. For example, a carboxylic acid with an EWG exhibits increased acidity due to the withdrawal of electron density, promoting resonance in the conjugate base. Conversely, electron-donating groups (EDG) reduce acidity by destabilizing the conjugate base. EDGs donate electron density, hindering resonance stabilization. Therefore, the impact of substituents on carboxylic acid acidity is contingent on their electron-withdrawing or electron-donating nature, influencing the stability of the resulting conjugate base.