Match List-I with List-II
|
List-I Name Reaction |
List-II Reagent |
|
(A) Rosenmund Reaction |
(I) \( CO/HCl \), anhyd. \( AlCl_3, CuCl \) |
|
(B) Stephen Reaction |
(II) \( CrO_2Cl_2 \) |
|
(C) Etard Reaction |
(III) \( SnCl_2 \) and \( HCl \) |
|
(D) Gatterman Koch Reaction |
(IV) \( H_2,Pd-BaSO_4 \) |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A)-(IV), (B)-(III), (C)-(II), (D)-(I)
All four named reactions are methods of preparing aldehydes; they differ in the starting compound:
from an acyl chloride, by partial hydrogenation (Rosenmund);
from a nitrile, by reduction to an imine and hydrolysis (Stephen);
from the methyl group of toluene, by partial oxidation (Etard);
from benzene itself, by formylation of the ring (Gattermann–Koch).
(A) Rosenmund Reaction — This matches (IV) \(H_2,Pd-BaSO_4\). An acyl chloride is hydrogenated over palladium on barium sulphate; the catalyst is poisoned so that the reduction stops at the aldehyde:
\( \displaystyle \ce{R-COCl + H2} \xrightarrow{\ce{Pd-BaSO4}} \ce{R-CHO + HCl} \)
(B) Stephen Reaction — This matches (III) \(SnCl_2\) and \(HCl\). Stannous chloride and HCl reduce the nitrile to an imine, which is hydrolysed to the aldehyde:
\( \displaystyle \ce{R-C#N} \xrightarrow{\ce{SnCl2 + HCl}} \ce{R-CH=NH} \xrightarrow{\ce{H3O^+}} \ce{R-CHO} \)
(C) Etard Reaction — This matches (II) \(CrO_2Cl_2\). Chromyl chloride oxidises the methyl group of toluene to a chromium complex, which is hydrolysed to benzaldehyde:
\( \displaystyle \ce{C6H5CH3} \xrightarrow[\text{(ii) }\ce{H3O^+}]{\text{(i) }\ce{CrO2Cl2},\ \ce{CS2}} \ce{C6H5CHO} \)
(D) Gatterman Koch Reaction — This matches (I) \(CO/HCl\), anhyd. \(AlCl_3, CuCl\). Benzene is treated with carbon monoxide and hydrogen chloride in the presence of anhydrous aluminium chloride and cuprous chloride:
\( \displaystyle \ce{C6H6 + CO + HCl} \xrightarrow{\text{anhyd. }\ce{AlCl3}/\ce{CuCl}} \ce{C6H5CHO} \)
Shortcut: (A)-(IV) appears only in Option (1).