Logo
Jeeify
MCQMediumJEE 2026Ethers

JEE Chemistry 2026 Question with Solution

A mixed ether (P), when heated with excess of hot concentrated hydrogen iodide produces two different alkyl iodides which when treated with aq. NaOH give compounds (Q) and (R) give yellow precipitate with NaOI. Identify the mixed ether (P):

  • A
    Skeletal structure of a mixed ether with an ethyl group on the left and a branched tert-amyl type alkyl group on the right connected through oxygen.
  • B
    Skeletal structure of isopropyl sec-butyl ether, showing two different secondary alkyl groups connected through an oxygen atom.
  • C
    Skeletal structure of a mixed ether containing an ethyl group on one side and a phenyl-substituted secondary alkyl group on the other.
  • D
    Skeletal structure of a mixed ether containing a phenethyl group on one side and a sec-butyl group on the other.

Answer

Correct answer:B

Step-by-step solution

Standard Method

Given: A mixed ether P on cleavage with excess hot concentrated HI gives two different alkyl iodides. On treatment with aqueous NaOH, these give compounds Q and R, both of which give yellow precipitate with NaOI.

Find: The correct mixed ether P.

Ethers cleave with HI to form alkyl iodides. Hydrolysis of those alkyl iodides gives the corresponding alcohols.

The iodoform test is positive for alcohols containing the group CH3−CH(OH)−\mathrm{CH_3-CH(OH)-}.

From the solution, Option 2 is isopropyl sec-butyl ether.

Cleavage with HI gives isopropyl iodide CH3CHICH3\mathrm{CH_3CHICH_3} and sec-butyl iodide CH3CHICH2CH3\mathrm{CH_3CHICH_2CH_3}.

Hydrolysis gives isopropyl alcohol (2-propanol) and 2-butanol.

Both 2-propanol and 2-butanol contain the required CH3−CH(OH)−\mathrm{CH_3-CH(OH)-} group, so both give a positive iodoform test.

Also, this ether is mixed because the two alkyl groups are different.

Therefore, the correct option is B.

Common mistakes

  • Assuming that any alcohol formed after hydrolysis gives the iodoform test. This is wrong because the test is specific to compounds containing the CH3CO−\mathrm{CH_3CO-} or CH3−CH(OH)−\mathrm{CH_3-CH(OH)-} group. Always check the functional group in each alcohol.

  • Ignoring that the ether must be mixed. This is wrong because the question requires two different alkyl groups attached to oxygen. Verify that the ether contains two non-identical groups before testing the products.

  • Checking only one cleavage product for the iodoform test. This is wrong because both compounds Q and R are stated to give yellow precipitate with NaOI. Both alcohols formed after hydrolysis must satisfy the iodoform condition.

Practice more Ethers questions

Get unlimited AI-adaptive practice, mastery tracking, and an AI tutor that explains every step — free to start.

Start free trialMore on Ethers

Related questions