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Basics of Organic Chemistry question

2025 · 29 Jan · Shift 1 · Q17
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Basics of Organic Chemistry question

2025 · 29 Jan · Shift 1 · Q17

JEE MainChemistryBasics of Organic ChemistryMCQ+4 / −1

Match List - I with List - II.

List - I (Structure) List - II (IUPAC Name)
(A) JEE Main 2025 (Online) 29th January Morning Shift Chemistry - Basics of Organic Chemistry Question 31 English 1 (I) 4-Methylpent-1-ene
(B) (CH3)2C(C3H7)2 (II) 3-Ethyl-5-methylheptane
(C) JEE Main 2025 (Online) 29th January Morning Shift Chemistry - Basics of Organic Chemistry Question 31 English 2 (III) 4,4-Dimethylheptane
(D) JEE Main 2025 (Online) 29th January Morning Shift Chemistry - Basics of Organic Chemistry Question 31 English 3 (IV) 2-Methyl-1,3-pentadiene

Choose the correct answer from the options given below :

  1. A
    (A)-(II), (B)-(III), (C)-(IV), (D)-(I)
  2. B
    (A)-(II), (B)-(III), (C)-(I), (D)-(IV)
  3. C
    (A)-(III), (B)-(IV), (C)-(I), (D)-(II)
  4. D
    (A)-(III), (B)-(II), (C)-(I), (D)-(IV)
View written solutionFree

Correct answer: A

  1. We identify each structure in List-I and match it with the correct IUPAC name in List-II.

Step 1: Identify structure (B)

Given:

(CH3)2C(C3H7)2(\mathrm{CH_3})_2\mathrm{C}(\mathrm{C_3H_7})_2(CH3​)2​C(C3​H7​)2​

This means one central carbon is attached to:

  • two methyl groups,
  • two propyl groups.

So the skeleton is:

CH3−CH2−CH2−C(CH3)2−CH2−CH2−CH3\mathrm{CH_3-CH_2-CH_2-C(CH_3)_2-CH_2-CH_2-CH_3}CH3​−CH2​−CH2​−C(CH3​)2​−CH2​−CH2​−CH3​

The longest chain has 777 carbons ⇒ \Rightarrow⇒ heptane. At carbon 444, there are two methyl substituents.

Hence the name is:

4,4-Dimethylheptane\boxed{4,4\text{-Dimethylheptane}}4,4-Dimethylheptane​

So,

(B)→(III)(B) \to (III)(B)→(III)

Step 2: Use options to narrow remaining matches

Only options A and B have:

(B)→(III)(B)\to(III)(B)→(III)

So the answer must be either A or B.

Difference between A and B is in matching of (C) and (D):

  • Option A: (C)→(IV)(C)\to(IV)(C)→(IV) and (D)→(I)(D)\to(I)(D)→(I)
  • Option B: (C)→(I)(C)\to(I)(C)→(I) and (D)→(IV)(D)\to(IV)(D)→(IV)

So we now identify (C) and (D).


Step 3: Identify the alkene/diene structures

From the given list, the two remaining names are:

  • (I) 444-Methylpent-111-ene
  • (IV) 222-Methyl-1,31,31,3-pentadiene

Name (I): 444-Methylpent-111-ene

Main chain: pent-111-ene

CH2=CH−CH2−CH(CH3)−CH3\mathrm{CH_2=CH-CH_2-CH(CH_3)-CH_3}CH2​=CH−CH2​−CH(CH3​)−CH3​

This has one double bond.

Name (IV): 222-Methyl-1,31,31,3-pentadiene

Main chain: penta-1,31,31,3-diene

CH2=C(CH3)−CH=CH−CH3\mathrm{CH_2=C(CH_3)-CH=CH-CH_3}CH2​=C(CH3​)−CH=CH−CH3​

This has two double bonds.

Thus:

  • the structure with two double bonds must match (IV),
  • the structure with one double bond must match (I).

From the given figure, structure (C) is the diene and structure (D) is the mono-alkene. Therefore,

(C)→(IV),(D)→(I)(C)\to(IV), \qquad (D)\to(I)(C)→(IV),(D)→(I)

Step 4: Identify structure (A)

Now only name (II) remains for (A).

Name (II) is:

3-Ethyl-5-methylheptane3\text{-Ethyl-}5\text{-methylheptane}3-Ethyl-5-methylheptane

So,

(A)→(II)(A)\to(II)(A)→(II)

Step 5: Final matching

Thus the correct matching is:

(A)→(II),(B)→(III),(C)→(IV),(D)→(I)(A)\to(II), \quad (B)\to(III), \quad (C)\to(IV), \quad (D)\to(I)(A)→(II),(B)→(III),(C)→(IV),(D)→(I)

This corresponds to Option A.


Step 6: Compare with stored correct answer

Stored correct answer: A

Our derived answer: A

So they agree.

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