What is the reaction of benzoic acid with sodium hydroxide?
benzene-COOH + NaOH -> benzene-COO-Na + H2O
Sodium benzoate is a salt of a weak acid (benzoic acid). In water, sodium benzoate hydrolyses to form a strong base (sodium hydroxide) and benzoinc acid. This is an equilibrium reaction. Benzoic acid being a weak acid is only partially ionized in water whilst sodium hydroxide is fully ionoized. The resultant solution is therefore alkaline since the concentration of hydroxyl ions is greater than the concentration of hydrogen ions. The addittion of hydrochloric acid results…
Why is it necessary to extract ether layer with sodium hydroxide when reacting benzoic acid with hydroxide ion?
It depends on the overall reaction. If the carboxylic acid is an impurity in the reaction (undesired), then washing with sodium hydroxide will extract the carboxylic into the aqueous layer, and it can then be disposed. The reaction for this looks as follows: (ring)-COOH + NaOH -> (ring)-COO-Na+ + H20 Where the ring loses a proton to the hydroxide ion and becomes water soluble.