Final answer:
Carboxylic acids are normally found in the organic layer during extraction but turn into carboxylates that reside in the aqueous layer upon reaction with a base.
Step-by-step explanation:
In the extraction procedure with a carboxylic acid such as benzoic or toluic acid using water and an organic solvent like diethyl ether, the carboxylic acid typically resides in the organic layer due to its nonpolar nature. However, when a base is added to form the corresponding carboxylate, the carboxylic acid loses a proton, becoming an anion, which is more soluble in water. Consequently, the carboxylate will be found predominantly in the aqueous layer due to its increased polarity and ionic character.