See image — IUPAC and Nomenclature Chemistry Question

💡 Solution & Explanation

Step 1: Identify the structure. The compound shown is NC-CH2-CH2-CN, i.e., two -CH2-CN groups connected to each other. This gives the connectivity: NC-CH2-CH2-CN, which is a two-carbon chain (ethane backbone) each end bearing a -CN (nitrile) group. Step 2: Determine the parent chain and functional group naming. In IUPAC nomenclature for nitriles, when the CN carbon is NOT included in the parent chain (i.e., the CN is treated as a suffix '-carbonitrile'), we count only the carbon atoms in the chain excluding the CN carbons. Alternatively, when CN carbons ARE included in the parent chain, the suffix '-nitrile' or '-dinitrile' is used. Step 3: Count the carbons. The full chain is: N≡C-CH2-CH2-C≡N. Including the CN carbons, this is a 4-carbon chain (butane backbone: C1≡N, C2H2, C3H2, C4≡N). The CN groups are at positions 1 and 4. Since the CN carbons are included in numbering, the suffix is '-dinitrile' (not '-dicarbonitrile'). Step 4: Assign the name. The parent chain has 4 carbons (but-), with nitrile groups at C1 and C4: Butane-1,4-dinitrile. Step 5: Eliminate other options. (a) Butane-1,4-dicarbonitrile would imply 6 carbons total (4 in chain + 2 CN carbons), which is incorrect for this structure. (b) Ethane-1,2-dicarbonitrile would also imply 4 carbons total but uses 'dicarbonitrile' incorrectly here. (c) Ethane-1,2-dinitrile would mean only a 2-carbon chain with nitrile at C1 and C2, which does not match the 4-carbon structure. Therefore, the correct answer is D.