Hydrolysis of Acid Chloride | Acyl Chloride | Mechanism

Acid chloride such as ethanoyl chloride, benzoyl chloride hydrolysis easily in the water and give carboxylic acid and HCl as the products. We know carboxylic acid is a weak acid and HCl is a strong acid in the water.



Note that, acid chlorides are also named as acyl chlorides or carboxylic acid chlorides.


Acid chloride aqueous solution | Reaction of acid chloride and water

Aqueous acid chloride is a very acidic solution due to formation of a strong acid and a weak acid. This hydrolysis reaction is a elimination reaction and water is participated as a reagent. This reaction completely converts acid chloride to carboxylic acid and HCl.


Calculate pH of strong acid and weak acid solution

Some examples of hydrolysis of acyl chlorides are explained below.


Ethanoyl chloride and water reaction

Ethanoic acid and HCl are given as products by the hydrolysis of ethanoyl chloride. Ethanoyl chloride is soluble in water and form a strong acidic solution due to HCl acid.

carboxylic acid chloride and water reaction

Benzoyl chloride hydrolysis

Benzoyl chloride hydrolysis give benzoic acid and HCl as products. Benzoic acid is a white precipitate which is a not soluble organic compound in water.


Mechanism

  • We know, carbonyl carbon has positively charged and H2O is a good nucleophile.
  • Water molecule attacks the carbonyl carbon. It's going to form new C-O bond. With that step, two electrons of one bond of existed C=O bond is gone to the oxygen atom. See the mechanism figure.
  • Next. C-Cl bond is broken and Cl- is given. Existed C=O bond forms once again.
  • Now oxygen atom has a positive +1 charge. Oxygen does not like to hold positive charge die to higher electronegativity. So one O-H bond is broken and hydrogen atom is eliminated as H+.
  • Cl- combines with H+ to form HCl.
carboxylic acid chloride hydrolysis mechanism

Aqueous carboxylic acid chloride show following reactions also

  • Emits CO2 with Na2CO3 or NaHCO3
  • Add dilute HNO3 and AgNO3. It gives the AgCl, white precipitate.


Organic Chemistry Reactions for Grade 12 Chemistry