Rosenmund's reduction of an acid chloride gives?

Appeared in: KPSC Staff Nurse - 2018

Explanation

Rosenmund reduction is a hydrogenation process that specifically converts an acyl chloride (acid chloride) to an aldehyde.
The reaction utilizes a palladium catalyst supported on barium sulfate (Pd/BaSO₄).
This catalyst is intentionally 'poisoned' with a compound like sulfur or quinoline.
The purpose of the poison is to deactivate the catalyst partially, preventing the over-reduction of the newly formed aldehyde into a primary alcohol.
Therefore, the reaction selectively stops at the aldehyde stage, making it the final product.

Option A: An ester is formed through the reaction of an acid chloride with an alcohol (esterification), which is a substitution reaction, not a reduction.
Option B: An alcohol is the product of a more complete reduction. The poisoned catalyst in the Rosenmund reaction is specifically designed to prevent this over-reduction.
Option D: A hydrocarbon is the result of a complete deoxygenation of the carbonyl group, which is a much more drastic reduction than the Rosenmund reaction.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Named Reactions in Organic Chemistry as background academic context rather than a clinical decision trigger.
While not directly clinical, understanding selective reactions like Rosenmund reduction is fundamental to pharmaceutical chemistry.
Many drugs are complex organic molecules, and their synthesis requires precise, multi-step processes. The ability to stop a reaction at an intermediate stage (like an aldehyde) without it proceeding to an alcohol is crucial for building the correct molecular structure.
What if the catalyst wasn't poisoned? The reaction would produce an alcohol instead of an aldehyde. If the target molecule for a drug required an aldehyde group, the synthesis would fail, yielding an impurity or an entirely different, potentially inactive or harmful, substance.

How to Approach the Question

Identify the key terms in the question: 'Rosenmund's reduction' and 'acid chloride'.
Recognize that 'Rosenmund's reduction' is a specific, named reaction in organic chemistry.
Recall the definition of this reaction: it is the catalytic hydrogenation of an acid chloride to an aldehyde.
Evaluate the options based on this definition. An aldehyde is the direct product.
Consider why the other options are incorrect. An alcohol represents over-reduction, an ester is from a different reaction (esterification), and a hydrocarbon is from a much stronger reduction.
Select the option that matches the specific outcome of this controlled, partial reduction.

Concept Tested & Keywords

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Practise the full KPSC Staff Nurse - 2018

Attempt every question from this paper in a timed mock, then review the full solution for each one.