See image — Hydrocarbons Chemistry Question

💡 Solution & Explanation

Concept: When an alkyne undergoes ozonolysis (treatment with ozone followed by hydrolysis), the triple bond is cleaved and each carbon of the triple bond is converted into a carboxylic acid group (RCOOH). For a symmetrical internal alkyne R-C≡C-R, both fragments are identical, giving only one carboxylic acid product (2 equivalents of RCOOH). Reasoning: The target product is butanoic acid, CH3CH2CH2CO2H, which has 4 carbons. For butanoic acid to be the ONLY organic product, the alkyne must be a symmetrical internal alkyne where both sides of the triple bond are identical propyl (CH3CH2CH2-) groups. The alkyne would be: CH3CH2CH2-C≡C-CH2CH2CH3, which is 4-octyne (oct = 8 carbons, triple bond at C4). Verification: 4-Octyne is CH3CH2CH2-C≡C-CH2CH2CH3. Ozonolysis cleaves the triple bond: each carbon of the triple bond becomes a carboxyl group, giving CH3CH2CH2COOH + CH3CH2CH2COOH = only butanoic acid as the organic product. Since the molecule is symmetric, only one product forms. Why other options fail: - (a) 1-Butyne: CH3CH2C≡CH. Ozonolysis gives CH3CH2COOH (propanoic acid) + CO2 (or HCOOH from terminal carbon), not only butanoic acid. - (c) 1-Pentyne: CH3CH2CH2C≡CH. Ozonolysis gives CH3CH2CH2COOH (butanoic acid) + CO2/HCOOH. Not the ONLY product (CO2 or formic acid also formed). Also not a single organic product. - (d) 2-Hexyne: CH3-C≡C-CH2CH2CH3. Ozonolysis gives CH3COOH (acetic acid) + CH3CH2CH2COOH (butanoic acid) — two different products, not only butanoic acid. Therefore, the correct answer is B.