JEE Main 2025 · 29 January · morning · Single correct · +4 / −1
Match List - I with List - II.
Choose the correct answer from the options given below :
| List - I (Structure) | List - II (IUPAC Name) |
|---|---|
| (A) H₃C, -, CH₂, -, CH, -, CH₂, -, CH, -, C₂H₅; |, |; C₂H₅, CH₃ | (I) 4-Methylpent-1-ene |
| (B) (CH₃)₂C(C₃H₇)₂ | (II) 3-Ethyl-5-methylheptane |
| (C) | (III) 4,4-Dimethylheptane |
| (D) | (IV) 2-Methyl-1,3-pentadiene |
- (a) (A)-(II), (B)-(III), (C)-(IV), (D)-(I)
- (b) (A)-(II), (B)-(III), (C)-(I), (D)-(IV)
- (c) (A)-(III), (B)-(IV), (C)-(I), (D)-(II)
- (d) (A)-(III), (B)-(II), (C)-(I), (D)-(IV)
Answer and solution
Answer (a) (A)-(II), (B)-(III), (C)-(IV), (D)-(I)
Solution
Chemistry ma’am · 4 steps
Pick the longest chain, then number it so double bonds, then branches, get the lowest numbers.
- Structure A. The longest chain runs from the left CH₃ to the end of the right-hand ethyl group, which is 7 carbons, so the parent is heptane. The branches sit at 3 and 5 from either end. When the numbers tie, the group earlier in the alphabet gets the lower number, so ethyl takes C3: 3-ethyl-5-methylheptane.
- Structure B. Expand it: CH₃CH₂CH₂-C(CH₃)₂-CH₂CH₂CH₃. The two propyl groups and the central carbon make a 7-carbon chain, and both methyls sit on C4: 4,4-dimethylheptane.
- Structures C and D. Here the double bonds get the lowest numbers first. C is CH₂=C(CH₃)-CH=CH-CH₃, a 5-carbon chain with double bonds at C1 and C3 and a methyl on C2. D is CH₂=CH-CH₂-CH(CH₃)₂, a 5-carbon chain with one double bond at C1 and a methyl on C4.
Structure Parent chain Locants IUPAC name A heptane ethyl 3, methyl 5 (II) 3-Ethyl-5-methylheptane B heptane methyl 4, methyl 4 (III) 4,4-Dimethylheptane C (two C=C) pentadiene C=C at 1 and 3, methyl 2 (IV) 2-Methyl-1,3-pentadiene D (one C=C) pentene C=C at 1, methyl 4 (I) 4-Methylpent-1-ene - So. The match is (A)-(II), (B)-(III), (C)-(IV), (D)-(I), which is option (a).
The idea to keep. Main chain first, then lowest numbers for double bonds, then for branches. If the branch numbers still tie, the group earlier in the alphabet takes the lower number.
Answer from the NTA final answer key. Solution by PrepWiser.