Question

Write chemical test to distinguish between the following compounds:

Phenol and Benzoic acid

Give chemical test to distinguish between the following pair of compound:

Phenol and Benzoic acid

Answer 1

Phenol and Benzoic Acid can be distinguished by the iron chloride FeCl₃ test. As phenol gives violet colouration with neutral FeCl₃, solution while benzoic acid gives buff-coloured precipitate of ferric benzoate.

\[\ce{6C6H5OH + FeCl3 -> [\underset{Violet complex}{Fe(OC6H5)6]^{3-}} + 3H^{+} + 3HCl}\]

\[\ce{\underset{Benzoic acid}{3C6H5COOH} + FeCl3 -> \underset{Buff coloured ppt.}{(C6H5COO)3Fe} + 3HCl}\]

Answer 2

Reagent	Phenol	Benzoic acid
Neutral ferric chloride	When phenol is treated with ferric chloride, there is a change in colour; the product formed is either green, blue, purple, or red.	No change in the colour of benzoic acid.