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 the information:
- C₃H₆O is likely acetone (CH₃COCH₃), which is a ketone.
- Tollen's reagent is used to test for aldehydes, and acetone (a ketone) does not react with Tollen's reagent to form a silver mirror. This is characteristic of ketones (unlike aldehydes).
- Hydroxylamine reacts with ketones to form oximes. This reaction is typical for ketones. Based on this information, acetone (or another ketone with similar properties) is the compound being described. Let's evaluate the tests:
- Iodoform test: Ketones, particularly methyl ketones like acetone, give a positive Iodoform test (yellow precipitate of iodoform, CHI₃), so this test is positive for acetone.
- Fehling’s test: This test is used to detect aldehydes, not ketones, so it would be negative for acetone.
- Schiff’s test: This test is also used for aldehydes, not ketones, so it would be negative for acetone.
- Carbylamine test: Ketones do not react positively in the Carbylamine test, as this test is used for primary amines. Chemical Reactions: - Formation of Oxime with Hydroxylamine: When acetone reacts with hydroxylamine, an oxime is formed: \[ \text{CH}_3\text{COCH}_3 + \text{NH}_2\text{OH} \rightarrow \text{CH}_3\text{C=NOH}\text{CH}_3 \] - Iodoform Test for Acetone: The Iodoform test is positive for acetone (CH₃COCH₃) and other methyl ketones, resulting in the formation of a yellow precipitate of iodoform (CHI₃): \[ \text{CH}_3\text{COCH}_3 + 3 \text{I}_2 + 4 \text{NaOH} \rightarrow \text{CHI}_3 + \text{CH}_3\text{COONa} + 3 \text{NaI} + 3 \text{H}_2\text{O} \]
Thus, acetone reacts positively in the Iodoform test and gives a yellow precipitate. Diagram for the Reaction with Hydroxylamine: Here is the diagram illustrating the formation of an oxime from acetone and hydroxylamine: ```latex \begin{center} \includegraphics[width=0.6\textwidth]{q32_image.png} \end{center}