Question

The reagent used in Gatterman-Koch formylation of arene is

• A. $\text{CO}_2$, HCl
• B. $\text{CrO}_2\text{Cl}_2$
• C. CO, HCl
• D. DiBAl-H

Hint:

Associate the keywords "Koch" and "Formylation" directly with Carbon Monoxide (CO). The "C" and "O" letters in "Koch" can serve as a simple memory anchor for $\text{CO} + \text{HCl}$!

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The problem asks for the identity of the primary chemical reagents utilized in the Gatterman-Koch reaction to convert an arene (such as benzene) into its corresponding aromatic aldehyde.

Step 2: Detailed Explanation:
The Gatterman-Koch reaction is a variation of Friedel-Crafts acylation. In this reaction, benzene or its derivatives are treated with a gaseous mixture of carbon monoxide (CO) and hydrogen chloride (HCl) under high pressure in the presence of a catalyst like anhydrous aluminum chloride ($\text{AlCl}_3$) or cuprous chloride (CuCl). \includegraphics[width=0.7\linewidth]{images/11sol.png}
The mixture of CO and HCl essentially functions in situ to generate a transient formyl chloride species (HCOCl), which subsequently provides the active formyl electrophile ($\text{CHO}^+$) to attack the aromatic ring, yielding benzaldehyde as the primary product.

Step 3: Final Answer:
The reagents used in this reaction are CO and HCl, which corresponds to option (C).