See image — IUPAC and Nomenclature Chemistry Question

💡 Solution & Explanation

Concept: IUPAC nomenclature of carboxylic acids with unsaturation and aryl substituents. Step 1: Identify the parent chain. The compound is Ph-CH=CH-COOH. The principal characteristic group is the carboxylic acid (-COOH), which determines the parent chain and must be at C1. Step 2: Count the carbon chain including the -COOH carbon. C1 = COOH carbon, C2 = CH (double bond), C3 = CH (double bond, attached to Ph). This gives a 3-carbon chain: prop-enoic acid. Step 3: Locate the double bond. The double bond is between C2 and C3, so it is prop-2-enoic acid. Step 4: Identify the substituent. A phenyl group (Ph) is attached at C3, giving 3-phenyl prop-2-enoic acid. Step 5: Evaluate other options. - (b) '3-phenol prop-1-enoic acid' is incorrect: 'phenol' is wrong (should be 'phenyl'), and the double bond position is wrong (C1-C2 instead of C2-C3; also C1 is the COOH carbon so a double bond at C1 is impossible in this context). - (c) '3-carboxy-prop-1-ene benzene' is incorrect: this treats benzene as the parent, which is not appropriate when a higher-priority group (-COOH) is present, and the numbering is wrong. - (d) 'but-2-enoic acid' is incorrect: this implies a 4-carbon chain with no phenyl substituent (it would be CH3-CH=CH-COOH, i.e., crotonic acid). The correct IUPAC name is 3-phenyl prop-2-enoic acid. Therefore, the correct answer is A.