Question

The correct match between Item – I (Starting material) and Item – II (reagent) for the preparation of benzaldehyde is :

• A. (I) - (R), (II) - (P) and (III) - (Q)
• B. (I) - (P), (II) - (Q) and (III) - (R)
• C. (I) - (Q), (II) - (R) and (III) - (P)
• D. (I) - (R), (II) - (Q) and (III) - (P)

Answer 1

The correct option is A

(I) - (R), (II) - (P) and (III) - (Q)

The correct option is (A):

Explanation for the correct answer:-

(I) Benzene - (R) $\mathrm{CO},\mathrm{HCl}\mathrm{and}{\mathrm{AlCl}}_3$

1. So basically when benzene gets treated with the vapors of the Carbon monoxide and Hydrogen chloride in the presence of the catalyst mixture of the ${\mathrm{AlCl}}_3/\mathrm{CuCl}$ there would be formation of benzaldehyde.
2. This reaction basically takes place under the high pressure and is known as Gattermann-Koch aldehyde synthesis.
3. In this reaction actually there is the formation or the production of benzaldehyde from benzene.

(II) Benzonitrile - (P) $\mathrm{HCl}\mathrm{and}{\mathrm{SnCl}}_2.{\mathrm{H}}_3{\mathrm{O}}^{+}$

1. This is actually a chemical reaction in which the Alkyl nitriles on the reduction with Stannous chloride and also Hydrochloric acid in the presence of dry ether will give the imine hydrochlorides .
2. Further which on acid hydrolysis will correspondingly give aldehyde.
3. This reaction is actually known as Stephen's reaction.

(III) Benzoyl chloride - (Q) ${\mathrm{H}}_2,\mathrm{Pd}-{\mathrm{BaSO}}_4\mathrm{and}\mathrm{quinoline}$

1. This reaction is basically known as the Rosenmund reaction.
2. In this reaction the hydrogenation process will take place where the molecular Hydrogen will react with the Acyl chloride and in the presence of catalyst such as Palladium on the Barium sulfate.
3. This Barium sulfate will reduce the activity of the Palladium and further due to it's low surface area there would be prevention over the reduction.

Therefore,

Item -I	Item -II
(I) Benzene	(R) $\mathrm{CO},\mathrm{HCl}\mathrm{and}{\mathrm{AlCl}}_3$
(II) Benzonitrile	(P) $\mathrm{HCl}\mathrm{and}{\mathrm{SnCl}}_2.{\mathrm{H}}_3{\mathrm{O}}^{+}$
(III) Benzoyl chloride	(Q) ${\mathrm{H}}_2,\mathrm{Pd}-{\mathrm{BaSO}}_4\mathrm{and}\mathrm{quinoline}$