COMEDK · Chemistry · 27. Aldehydes and Ketones

Identify the Reagents I and II to be used in the course of the given reactions.

A \(\text { Reagent I: } \mathrm{Zn} / \mathrm{Hg} \text { in conc. } \mathrm{HCl} \quad \text { Reagent II: }\left[\mathrm{Ag}\left(\mathrm{NH}_3\right)_2\right]^{+}\)
B \(\text { Reagent I: } \mathrm{H}_2 / \mathrm{Pd}-\mathrm{BaSO}_4 \quad \text { Reagent II: } \mathrm{CrO}_3 /\left(\mathrm{CH}_3 \mathrm{CO}\right)_2\)
C \(\text { Reagent I: } \mathrm{NH}_2 \mathrm{NH}_2 / \mathrm{KOH} \quad \text { Reagent II: } \mathrm{Cr}_2 \mathrm{O}_7{ }^{2-} / \mathrm{H}^{+}\)
D \(\text { Reagent I: DIBAL- } \mathrm{H} / \mathrm{H}_2 \mathrm{O} \quad \text { Reagent II: conc. } \mathrm{KOH} / \text { heat }\)

Verified Solution

Answer & Solution

Correct Answer

(D) \(\text { Reagent I: DIBAL- } \mathrm{H} / \mathrm{H}_2 \mathrm{O} \quad \text { Reagent II: conc. } \mathrm{KOH} / \text { heat }\)

Step-by-step Solution

Detailed explanation

Starting material [A] is 1-chloro-1-formylcyclohexan-4-one. \(Cu^{2+}/OH^-\) oxidises the aldehyde to carboxylic acid (ketone unaffected). [B] = 1-chlorocyclohexan-4-one-1-carboxylic acid. \(C_2H_5OH/H^+\) esterifies the carboxylic acid. [C] = ethyl…

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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