See image — Hydrocarbons Chemistry Question

💡 Solution & Explanation

Concept: Red phosphorus (Red P) with HI is a strong reducing agent system commonly used in organic chemistry to reduce carbonyl compounds and alcohols by replacing oxygen-containing functional groups with hydrogen. Step 1: Identify the starting material. The starting material is propanal (CH3-CH2-CHO), an aldehyde with 3 carbons. Step 2: Understand the reagent. Red P + HI is a powerful reducing system. When an aldehyde (or ketone) is treated with Red P and HI, the carbonyl group (C=O) is completely reduced. The HI first reduces the aldehyde to the corresponding alcohol (propanal → propan-1-ol), and then Red P + HI further reduces the C-OH bond by replacing the -OH with -H (since HI converts -OH to -I, and then Red P reduces C-I to C-H). Step 3: Trace the reaction. Propanal (CH3CH2CHO) → [HI reduces C=O to CHOH] → propan-1-ol (CH3CH2CH2OH) → [Red P + HI replaces OH with H] → propane (CH3CH2CH3). Step 4: The net result is complete deoxygenation of the aldehyde, yielding the fully reduced alkane: propane (CH3CH2CH3). Why other options fail: - (b) Propanol: This would be an intermediate, but Red P + HI goes further to fully reduce the alcohol to the alkane. - (c) Propanoic acid: This would require oxidation, not reduction. - (d) Propene: Elimination would require different conditions; Red P + HI does not cause dehydration here. Therefore, the correct answer is A.