The major product of the following chemical reaction is :
R-CN $\xrightarrow{(1) H_3O^+, \Delta (2) SOCl_2 (3) Pd/BaSO_4, H_2}$ ?
(Using $R$ as the alkyl group from the prompt skeleton)
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Rosenmund Reduction ($Pd/BaSO_4$ with $S$ or quinoline) is a poisoned catalyst method that stops the reduction of acid chlorides at the aldehyde stage, preventing further reduction to alcohol.
The reaction given here involves a multi-step process starting with a nitrile group R-CN. To determine the major product, let's analyze each step involved in the reaction:
The first step involves hydrolysis of nitrile in the presence of acid and heat, H_3O^+, \Delta, converting it into a carboxylic acid. The reaction can be represented as:
R-CN \xrightarrow{H_3O^+, \Delta} R-COOH.
In the second step, the carboxylic acid (formed in the previous step) reacts with thionyl chloride SOCl_2 to form an acyl chloride:
R-COOH + SOCl_2 \rightarrow R-COCl + SO_2 + HCl.
The final step involves the reduction of the acyl chloride with the Rosenmund reduction method using Pd/BaSO_4 and hydrogen H_2. This results in the formation of an aldehyde:
R-COCl + H_2 \xrightarrow{Pd/BaSO_4} R-CHO.
After these steps, the major product formed is an aldehyde.
Let's evaluate the given options based on the reactions concluded:
Alcohol: Formation of alcohol would require reducing the nitrile or carboxylic acid differently, not via acyl chloride to aldehyde.
Anhydride: Formation would require the reaction of two carboxylic acids or acyl chloride in the presence of a base or dehydrating agent, which is not part of the given sequence.
Alkane: Formation would require stronger reducing agents to go from nitrile to primary amine to alkane, not through the pathway provided.
Aldehyde: As explained through the stepwise reaction mechanism, aldehyde is the correct product.
