Complete Information about Iodoform Test | NEB Class 12 Chemistry

Introduction:

The iodoform test is a chemical test used to detect the presence of certain types of organic compounds in an unknown substance. This test is particularly useful for identifying carbonyl compounds with the structure R-CO-CH ₃ or alcohols with the structure R-CH(OH)-CH₃.

Iodoform Test Reaction For Alcohols:

CH₃-CH₂-OH + 6NaOH +4I₂ →CHI₃)(Iodoform) + HCOONa (Formic Acid) + 5NaI +5H₂O
Smell of Iodoform: Hospital Smell
Color of Iodoform: Yellow crystals

Iodoform Test Reaction For Aldehyde:

CH₃-CHO + 3I₂ + 4NaOH→CHI₃(Iodoform) + HCOONa (Formic Acid) + 3NaI +3H₂O
Smell of Iodoform: Hospital Smell
Color of Iodoform:Lemon Yellow crystals

Iodoform Test Reaction For Ketone:

CH₃-CO-CH₃ + 3I₂ + 4NaOH→CHI₃(Iodoform) + CH₃-COONa + 3NaI +3H₂O
Smell of Iodoform: Hospital Smell
Color of Iodoform:Lemon Yellow crystals

Most Asked Question in NEB Exam:

A. Which of the following does not give iodoform?

1. Acetic Acid
2. Lactic Acid
3. Acetophenone
4. Propionic Acid

Correct Answer is : i and iv
Acetic Acid and Propionic Acid

B. Why Carboxilic Acid Do not Give Iodoform Test

Carboxylic acids react as acid with the base and hence do not form CI3 because the C=O. in the COOH has delocalisation over the group.

C. Which type of alcohol gives iodoform test?

Only certain secondary alcohols that have a methyl group attached to the carbon atom next to the hydroxyl group (alpha position) will give a positive iodoform test. Primary alcohols do not give a positive iodoform test, except for ethanol.