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Hydrocarbons · Question 20

JEE Main 2026 (Online) 21st January Morning ShiftMCQMedium📈 Topic in 32% papers+4−1
1

Identify A in the following reaction. [figure]

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]

Answer

(1) [figure]

Solution

A 2H2/Pt decalin A has the decalin skeleton with two C=C bonds.

Hot KMnO4 cleaves each C=C; every =CH– carbon is oxidised to –COOH.

Products: cyclohexane-1,2-dicarboxylic acid + oxalic acid (HOOC-COOH).

One ring (the cyclohexane ring of the product) is saturated and is not broken.

Both C=C are in the other ring as a diene C1=C2-C3=C4, with C1 and C4 bonded to the two ring-fusion carbons.

Cleavage of C1=C2 and C3=C4: C1, C4 → two –COOH on adjacent ring carbons; C2-C3 → HOOC-COOH.

This is structure (1).

(2): one double bond is at the ring fusion – its cleavage opens both rings (no cyclohexane-1,2-dicarboxylic acid).

(3), (4): one double bond in each ring – both rings are cleaved and no oxalic acid is formed.

Answer: (1)

JEE Main 2026 (Online) 21st January Morning Shift

Keep practising — Hydrocarbons

2

[figure] 'P' is

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
JEE Main 2025 (Online) 8th April Evening Shift
3

Choose the correct set of reagents for the following conversion. [figure]

  1. Cl2/ anhy. AlCl3; Br2/Fe; alc. KOH
  2. Cl2/Fe; Br2/ anhy. AlCl3; aq. KOH
  3. Br2/Fe; Cl2, ; alc. KOH
  4. Br2/ anhy. AlCl3; Cl2, ; aq. KOH
JEE Main 2025 (Online) 8th April Evening Shift
4

Given below are two statements: In the light of the above statements, choose the correct answer from the options given below

  1. Statement I is false but Statement II is true
  2. Both Statement I and Statement II are false
  3. Statement I is true but Statement II is false
  4. Both Statement I and Statement II are true
JEE Main 2025 (Online) 7th April Morning Shift
5

Identify the structure of the final product (D) in the following sequence of the reactions : [figure] Total number of sp2 hybridised carbon atoms in product D is .

JEE Main 2025 (Online) 7th April Evening Shift
6

Predict the major product of the following reaction sequence: [figure]

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
JEE Main 2025 (Online) 4th April Morning Shift
7

Consider the following molecule(X). [figure] The major product formed when the given molecule (X) is treated with HBr (1 eq) is :

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
JEE Main 2025 (Online) 4th April Evening Shift
8

Which compound would give 3-methyl-6-oxoheptanal upon ozonolysis?

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
JEE Main 2025 (Online) 3rd April Morning Shift
9

An optically active alkyl halide C4H9Br [A] reacts with hot KOH dissolved in ethanol and forms alkene [B] as major product which reacts with bromine to give dibromide [C]. The compound [C] is converted into a gas [D] upon reacting with alcoholic NaNH2. During hydration 18 gram of water is added to 1 mole of gas [D] on warming with mercuric sulphate and dilute acid at 333 K to form compound [E]. The IUPAC name of compound [E] is :

  1. Butan-2-ol
  2. But-2-yne
  3. Butan-2-one
  4. Butan-1-al
JEE Main 2025 (Online) 2nd April Morning Shift
10

Given below are two statements: In the light of the above statements, choose the most appropriate answer from the options given below:

  1. Statement I is incorrect but Statement II is correct
  2. Both Statement I and Statement II are correct
  3. Statement I is correct but Statement II is incorrect
  4. Both Statement I and Statement II are incorrect
JEE Main 2025 (Online) 2nd April Evening Shift
11

A molecule (P) on treatment with acid undergoes rearrangement and gives (Q). (Q) on ozonolysis followed by reflux under alkaline condition gives (R). The structure of (R) is given below. [figure] The structure of (P) is

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
JEE Main 2025 (Online) 28th January Morning Shift

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