JEE Main 2026 — Jan 23, Shift 2 — Chemistry solution

JEE Main2026Jan 23, Shift 2Chemistry

Iodoform test can differentiate between

A. Methanol and Ethanol

B. $C H_{3} C O O H$ and $C H_{3} C H_{2} C O O H$

C. Cyclohexene and cyclohexanone

D. Diethyl ether and Pentan-3-one

E. Anisole and acetone

Choose the correct answer from the options given below:

A
A & E only
B
A & D only
C
A, B & E only
D
B, C & E only

Solution

The iodoform test requires either a methyl ketone ( $C H_{3} - C O - R$ ) or a secondary alcohol of type $C H_{3} - C H (O H) - R$ (which is oxidised to the corresponding methyl ketone by $N a O I$ ). It also responds to ethanol and acetaldehyde.

(A) Methanol gives no iodoform; ethanol gives a positive test (yellow ppt). Distinguishable.

(B) Neither $C H_{3} C O O H$ nor $C H_{3} C H_{2} C O O H$ contains the required structural unit; both give a negative test. Not distinguishable.

(C) Cyclohexene (alkene) and cyclohexanone (cyclic ketone with no $- C O C H_{3}$ ) both give negative tests. Not distinguishable.

(D) Diethyl ether gives no test; pentan-3-one ( $C H_{3} C H_{2} - C O - C H_{2} C H_{3}$ ) lacks the methyl ketone group and gives no test. Not distinguishable.

(E) Anisole ( $C_{6} H_{5} - O C H_{3}$ ) gives no test; acetone ( $C H_{3} - C O - C H_{3}$ ) gives a positive test. Distinguishable.

Only A and E can be differentiated.

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