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Hydrocarbons · Question 28

JEE Main 2025 (Online) 2nd April Morning ShiftMCQMedium📈 Topic in 26% papers+4−1
1

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

Answer

(3) Butan-2-one

Solution

The only optically active C4H9Br is 2-bromobutane: [A] = CH3- *CHBr-CH2-CH3

[A] alc. KOH, [B] = CH3-CH=CH-CH3 (but-2-ene, Saytzeff product)

[B] Br2 [C] = CH3-CHBr-CHBr-CH3 (2,3-dibromobutane)

[C] alc. NaNH2 [D] = CH3-C C-CH3 (but-2-yne, gas) by double dehydrohalogenation

[D] [333 K] H2O, Hg2+/H+ CH3-C(OH)=CH-CH3 (enol) CH3-CO-CH2-CH3

[E] = butan-2-one

Answer: (3)

JEE Main 2025 (Online) 2nd April Morning Shift

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2

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
3

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
4

Identify product [A], [B] and [C] in the following reaction sequence. CH3-C CH [H2]Pd/C [A] [(ii) Zn, H2O](i) O3 [B] + [C]

  1. [A]: CH3-CH=CH2, [B]: CH3CHO, [C]: CH3CH2OH
  2. [A]: CH3-CH=CH2, [B]: CH3CHO, [C]: HCHO
  3. [A]: CH3CH2CH3, [B]: CH3CHO, [C]: HCHO
  4. [A]: CH2=CH2, [B]: H3C- O \|C-CH3, [C]: HCHO
JEE Main 2025 (Online) 28th January Evening Shift

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