See image — IUPAC and Nomenclature Chemistry Question

💡 Solution & Explanation

Step 1: Identify the functional group and parent chain. The molecule contains a -COOH (carboxylic acid) group. The carboxylic acid carbon is C1. Step 2: Trace the longest carbon chain containing the COOH group and both double bonds. Starting from the COOH carbon (C1), we go to C2 which bears a double bond (C2=C3, with a methyl branch at C2), then C3, C4, C5, C6 which bears another double bond (C5=C6, with a methyl branch at C6), then C7. Step 3: Identify the structure more carefully. The structure shows: - C1: COOH - C2=C3: double bond (one alkenyl arm going up, with methyl at C2) - C5=C6: double bond (another alkenyl arm going down, with methyl at C6) - C7: terminal carbon (methyl from the isopropylidene group) This gives a 7-carbon chain (heptanoic acid backbone) with double bonds at positions 2 and 5, and methyl groups at positions 2 and 6: 2,6-dimethylhepta-2,5-dienoic acid. Step 4: Number the chain to give the COOH the lowest locant (C1). The double bonds are at C2-C3 and C5-C6, methyl substituents are at C2 and C6. Step 5: Construct the name: parent chain = heptadienoic acid; double bonds at 2,5; methyls at 2,6 → 2,6-dimethylhepta-2,5-dienoic acid. Step 6: Why other options fail: - (b) 3,7-Dimethylhepta-2,5-dienoic acid: incorrect numbering/position of methyls. - (c) 1-Hydroxy-2,6-dimethylhepta-2,5-dienone: treats as a ketone with hydroxyl, but the functional group is COOH (carboxylic acid), not a ketone plus alcohol. - (d) none of these: incorrect since option (a) is correct. Therefore, the correct answer is A.