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Hydrocarbons

JEE Main 2025 (Online) 4th April Evening ShiftMCQMedium📈 Topic in 28% papers+4−1
Ques. 1JEE Main 2025, 4 April (Evening Shift)

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]

Answer

(1) [figure]

Solution

X has three C=C bonds; 1 equivalent of HBr adds to only one of them by electrophilic addition (H+ first, then Br-). The C=C giving the most stable carbocation reacts.

• C=C in the six-membered ring: protonation gives a secondary carbocation.

• C=C in the upper-left five-membered ring: protonation gives a secondary carbocation.

• C=C in the lower five-membered ring is trisubstituted (one carbon is the ring-fusion carbon). H+ adds to the CH carbon (Markovnikov's rule), giving a tertiary carbocation on the ring-fusion carbon (stabilised by +I effect and hyperconjugation of three alkyl groups).

3° carbocation > 2° carbocation, HBr adds to this double bond.

Br- attacks the tertiary carbocation Br on the ring-fusion carbon; the other two C=C bonds remain unchanged.

Answer: (1)

Keep practising — Hydrocarbons

Ques. 2JEE Main 2025, 3 April (Morning Shift)

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

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  4. [figure]
Ques. 3JEE Main 2025, 2 April (Morning Shift)

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
Ques. 4JEE Main 2025, 2 April (Evening Shift)

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
Ques. 5JEE Main 2025, 29 January (Evening Shift)

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 true but Statement II is false
  2. Both Statement I and Statement II are true
  3. Both Statement I and Statement II are false
  4. Statement I is false but Statement II is true
Ques. 6JEE Main 2025, 29 January (Evening Shift)

Isomeric hydrocarbons negative Baeyer's test (Molecular formula C9H12) The total number of isomers from above with four different non-aliphatic substitution sites is -

Ques. 7JEE Main 2025, 28 January (Morning Shift)

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]
Ques. 8JEE Main 2025, 28 January (Evening Shift)

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
Ques. 9JEE Main 2025, 24 January (Morning Shift)

The product (A) formed in the following reaction sequence is [figure]

  1. CH3-CH2- OH |CH-CH2-NH2
  2. CH3-CH2- NH2 |CH-CH2-NH2
  3. CH3- CH3 | OH |C-CH2-NH2
  4. CH3- CH3 | NH2 |C-CH2-OH
Ques. 10JEE Main 2025, 24 January (Morning Shift)

Following are the four molecules "P", "Q", "R" and "S". Which one among the four molecules will react with H-Br(aq) at the fastest rate? [figure]

  1. Q
  2. S
  3. P
  4. R
Ques. 11JEE Main 2025, 24 January (Evening Shift)

Identify correct statement/s : Choose the correct answer from the options given below :

  1. A, C and D only
  2. A, B and E only
  3. A and C only
  4. A only

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