Question

C$_3$H$_6$O does not form a silver mirror with Tollen’s reagent but forms an oxime with hydroxylamine. It can give positive:

• A. Iodoform test
• B. Fehling’s test
• C. Schiff’s test
• D. Carbylamine test

Hint:

The Iodoform test is a specific test for methyl ketones, like acetone, that produces a yellow precipitate of iodoform (CHI₃). The carbylamine test, Schiff’s test, and Fehling’s test are typically negative for ketones.

Answer 1

The Correct Option is A

Given Information:

• C₃H₆O is likely acetone (CH₃COCH₃), which is a ketone.
• Tollens’ reagent is used to test for aldehydes. Acetone, being a ketone, does not give a silver mirror.
• Hydroxylamine reacts with ketones to form oximes, which is characteristic of ketones.

Evaluation of Chemical Tests:

• Iodoform test: Methyl ketones like acetone give a positive iodoform test, producing a yellow precipitate of iodoform (CHI₃).
• Fehling’s test: This test detects aldehydes and is negative for ketones like acetone.
• Schiff’s test: This test is specific for aldehydes and gives a negative result for acetone.
• Carbylamine test: This test is specific for primary amines and is negative for ketones.

Chemical Reactions:

1. Formation of Oxime with Hydroxylamine:
When acetone reacts with hydroxylamine, an oxime is formed:

CH₃COCH₃ + NH₂OH → CH₃C(=NOH)CH₃

2. Iodoform Test for Acetone:
Acetone gives a positive iodoform test, forming a yellow precipitate of iodoform (CHI₃):

CH₃COCH₃ + 3I₂ + 4NaOH → CHI₃ + CH₃COONa + 3NaI + 3H₂O

Conclusion:
Acetone reacts positively in the iodoform test and forms an oxime with hydroxylamine, confirming that the compound is a methyl ketone.