Question

The oxidation of toluene with $Cr{O_3}$ in the presence of ${\left( {C{H_3}CO} \right)_2}O$ gives a product A, which on treatment with aqueous$NaOH$, produces?
A.${C_6}{H_5}COONa$
B.$2,4 - {\text{diacetyl toluene}}$
C.${C_6}{H_5}CHO$
D.${\left( {{C_6}{H_5}CO} \right)_2}O$

Answer 1

Hint: Chromic oxide is a bright green powder which mild oxidizing agent which is used to oxidize toluene in presence of acetic anhydride${\left( {C{H_3}CO} \right)_2}O$.

Complete step by step answer:
Toluene is also known as methylbenzene. It is an aromatic compound in which one methyl group is attached to a benzene ring. Its properties are-
It is in the form of a clear, colorless liquid with a characteristic sweet aroma.
Its vapours are heavier than air hence it floats on water.
It is insoluble in water but soluble in organic solvents like chloroform, ether, acetic acid and acetone.
It is a potentially toxic compound as its inhalation or ingestion may be toxic to our health.
When toluene reacts with $Cr{O_3}$ in the presence of${\left( {C{H_3}CO} \right)_2}O$, toluene is oxidized and it forms an intermediate known as benzylidene diacetate. When this intermediate reacts with aqueous $NaOH$, it changes into $Ph - CH{\left( {OH} \right)_2}$ where Ph- indicates phenyl group. Then the water molecule is removed from the product and benzaldehyde is formed. The reaction is given as-
$Ph - C{H_3}\xrightarrow[{{{\left( {C{H_3}CO} \right)}_2}O}]{{Cr{O_3}}}Ph - CH{\left( {OH} \right)_2}{\left( {C{H_3}CO} \right)_2}\xrightarrow{{Aqueous{\text{ }}NaOH}}Ph - CH{\left( {OH} \right)_2}\xrightarrow[{ - {H_2}O}]{}Ph - CHO$Here the benzaldehyde does not further oxidize into benzoic acid because chromic oxide is a mild oxidizing agent.

Hence the correct answer is C.

Note:
Benzaldehyde is an aromatic compound with an aldehyde functional group and it has an almond like odor. It is used in following ways-
-It is used as a flavouring agent.
-It is used as a preservative in cosmetics and personal care products.
-It is used as a solvent for oils and in synthetic perfumes and soaps.
-It is used in the manufacture of triphenyl-methane dyes.