See image — IUPAC and Nomenclature Chemistry Question

💡 Solution & Explanation

Step 1: Identify the longest carbon chain containing the principal characteristic group (carboxylic acid) and the maximum number of substituents. The molecule has a carboxylic acid (-COOH) at one end. Counting the main chain: starting from the carbonyl carbon of -COOH as C1, we trace the longest chain that also incorporates the terminal alkyne. The main chain contains 12 carbons total, ending in a terminal triple bond (C11≡C12), making it a dodec-11-ynoic acid. Step 2: Identify the parent chain name. The 12-carbon chain with a terminal alkyne at C11-C12 and a carboxylic acid at C1 gives the base name: dodec-11-ynoic acid. Step 3: Identify and number the substituents. There are six ethynyl groups (-C≡CH) attached to the main chain. Looking at the structure, these are located at carbons 4, 5, 6, 7, 8, and 9. Step 4: Verify the numbering gives substituents the lowest possible locants. With -COOH at C1 (fixed as the principal characteristic group), the six ethynyl groups at C4–C9 and the chain triple bond at C11 is consistent with lowest locant assignment. Step 5: Construct the full IUPAC name. Six ethynyl substituents at positions 4,5,6,7,8,9 on a dodec-11-ynoic acid backbone: 4,5,6,7,8,9-hexaethynyldodec-11-ynoic acid. The prefix 'hexa' indicates six ethynyl groups; 'ethynyl' is the -C≡CH substituent name; 'dodec' indicates 12 carbons in the main chain; '11-yn' locates the triple bond in the main chain at C11-C12; 'oic acid' indicates the carboxylic acid terminus. Therefore, the correct answer is 4,5,6,7,8,9-hexaethynyldodec-11-ynoic acid.