Question

(a) Write the structures of the main products of above reactions :
(b) Give chemical tests to distinguish between :
(i) Phenol and benzoic acid

(ii) Benzophenone and Acetophenone

Answer 1

(b) (i) Phenol and benzoic acid can be distinguished by ferric chloride test.

Ferric chloride test:

Phenol reacts with neutral $FeC{l}_3$ to form ferric phenoxide complex giving violet colouration.

$6C_6{H}_{5}OH+FeC{l}_3\to \left[Fe\right(O{C}_6{H}_5{)}_6{]}^{3-}+3H^{+}+3C{l}^{-}$

Phenol trace-phenol complex

(violet colour)

But benzoic acid reacts with neutral $FeC{l}_3$ to give a buff-coloured precipitation of benzoate.

$3C_6{H}_{5}OH+FeC{l}_3⟶(C_6{H}_{5}COO{)}_{3}Fe+3HCl$

Benzoic acid Ferric benzoate

(Baff coloured ppt)

(ii) Benzophenone $\left(C_6{H}_{5}CO{C}_6{H}_5\right)$ and acetophenone $\left(C_6{H}_{5}COC{H}_3\right)$ can be distinguished by iodoform test.

Acetophenone, being a methyl ketone on treatment with $I_2/NaOH$ undergoes iodoform reaction to give a yellow ppt. of iodoform. On the other hand, benzaldehyde does not give this test.

$C_6{H}_{5}COC{H}_3+3NaOI$

Acetophenone

$\downarrow$

$C_6{H}_{5}COONa+CH{I}_3\downarrow +2NaOI$

Iododorm

$C_6{H}_{5}CO{C}_6{H}_5\stackrel{NaOI}{⟶}$ No yellow ppt

(a) (i), (ii) and (iii) - Ref image