Identify A, X, Y, and Z in the reaction sequence involving Ethanal (A):
1. A → X (Reduction)
2. A → Y (Aldol

Question

Identify A, X, Y, and Z in the reaction sequence involving Ethanal (A): 
1. A → X (Reduction) 
2. A → Y (Aldol Condensation) 
3. A → Z (Reaction with Semicarbazide)

Accepted Answer

Based on the options and standard reactions of aldehydes found in the NCERT curriculum:
1.  **Compound A (Ethanal/Acetaldehyde):** The central reactant.
2.  **Product X (Ethanol):** Formed by the **reduction** of Ethanal using reducing agents like $NaBH_4$, $LiAlH_4$, or catalytic hydrogenation ($CH_3CHO + H_2 \rightarrow CH_3CH_2OH$).
3.  **Product Y (But-2-enal):** Formed by the **Aldol Condensation** of two molecules of Ethanal in the presence of dilute alkali, followed by dehydration upon heating. 
    $$ 2CH_3CHO \xrightarrow{dil. NaOH} CH_3CH(OH)CH_2CHO \xrightarrow{\Delta} CH_3CH=CHCHO + H_2O $$
4.  **Product Z (Semicarbazone):** Formed by the nucleophilic addition-elimination reaction of Ethanal with **Semicarbazide** ($NH_2CONHNH_2$) in a weakly acidic medium.
    $$ CH_3CHO + NH_2CONHNH_2 \rightarrow CH_3CH=NNHCONH_2 + H_2O $$

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