COMEDK · Chemistry · 27. Aldehydes and Ketones

Which of the following is NOT TRUE about nucleophilic addition reactions of aldehydes?

A Hemiacetals are gem-dialkoxy compounds
B The hydrogensulphite addition product is useful for separation and purification of aldehydes
C Aldehydes and ketones react very slowly with pure HCN to yield cyanohydrins
D 2,4 DNP derivatives are useful to identify aldehydes and ketones

Verified Solution

Answer & Solution

Correct Answer

(A) Hemiacetals are gem-dialkoxy compounds

Step-by-step Solution

Detailed explanation

Hemiacetals contain one alkoxy group (\(-OR\)) and one hydroxyl group (\(-OH\)) attached to the same carbon atom. They are gem-alkoxyalcohols. Acetals contain two alkoxy groups attached to the same carbon atom and are known as gem-dialkoxy compounds. Thus, the statement that…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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