See image — IUPAC and Nomenclature Chemistry Question

💡 Solution & Explanation

Concept: IUPAC nomenclature requires selecting the longest carbon chain that includes the principal characteristic group (aldehyde, -CHO) as the parent chain, then numbering to give the principal group the lowest locant. Step 1: Identify the principal characteristic group. The compound contains an aldehyde (-CHO), which is the highest-priority group and must be included in the parent chain. Step 2: Identify the longest carbon chain containing the -CHO group. The chain is: CH3-CH(-)-CHO, which is a 3-carbon chain (propanal backbone: C1=CHO, C2=CH, C3=CH3). Step 3: Number the chain. The aldehyde carbon is always C1. So C1 = CHO, C2 = CH (bearing the phenyl group), C3 = CH3. Step 4: Name the substituent. There is a phenyl group (C6H5-) on C2. Step 5: Assemble the name. Parent chain = propanal (3 carbons with aldehyde at C1). Substituent = phenyl at C2. Full name = 2-Phenylpropanal. Why other options fail: - (a) '2-Phenylpropan-3-al' is incorrect because in a 3-carbon aldehyde, the aldehyde is always at C1, not C3. The locant '3' for the aldehyde is not valid IUPAC nomenclature. - (b) 'Formylethylbenzene' treats benzene as the parent, which is incorrect when an aldehyde chain can serve as the principal chain. - (d) 'Ethylformylbenzene' also incorrectly uses benzene as the parent and misdescribes the substituent. Therefore, the correct answer is C.