Compound 'A' `C_(5)H_(10)O` forms a phenyl hydrazone and gives a negative Tollen's reagent test and iodoform test. On reduction with Zn-Hg/HCl, compound A gives n-Pentane. The compound 'A' is

Options

A. Primary alcohol
B. Aldehyde
C. Secondary alcohol
D. Ketone.

Explanation

To determine the identity of compound 'A' with the molecular formula C₅H₁₀O, we can analyze the information given step by step.

### Step 1: Analyze the Molecular Formula
The molecular formula of compound 'A' is C₅H₁₀O. This indicates that it could be either an aldehyde or a ketone.

**Hint 1:** Remember that the presence of a carbonyl group (C=O) is characteristic of both aldehydes and ketones.

### Step 2: Formation of Phenylhydrazone
The fact that compound 'A' forms a phenylhydrazone indicates that it contains a carbonyl group. This is a characteristic reaction for both aldehydes and ketones.

**Hint 2:** Phenylhydrazones are formed when hydrazine reacts with carbonyl compounds.

### Step 3: Negative Tollen's Test
The negative Tollen's reagent test suggests that compound 'A' is not an aldehyde, as aldehydes typically give a positive result with Tollen's reagent. Therefore, compound 'A' must be a ketone.

**Hint 3:** Tollen's reagent is used to distinguish between aldehydes and ketones; aldehydes reduce it to metallic silver, while ketones do not.

### Step 4: Negative Iodoform Test
The negative iodoform test indicates that compound 'A' does not have a methyl ketone structure (RCOCH₃) or an alcohol that can be oxidized to form a methyl ketone. This further confirms that compound 'A' is a ketone but not a methyl ketone.

**Hint 4:** The iodoform test is used to identify methyl ketones and some alcohols; a negative result suggests the absence of these structures.

### Step 5: Reduction with Zn-Hg/HCl
When compound 'A' is reduced with zinc amalgam in the presence of HCl, it yields n-pentane. This suggests that compound 'A' is a ketone that, upon reduction, gives a straight-chain alkane.

**Hint 5:** The Clemmensen reduction (using Zn-Hg and HCl) converts ketones to alkanes.

### Step 6: Identify Compound 'A'
Given that compound 'A' is a ketone (C₅H₁₀O), does not give a Tollen's test or iodoform test, and reduces to n-pentane, the most likely structure for compound 'A' is 3-pentanone (or another ketone with a similar structure).

**Final Conclusion:** Compound 'A' is 3-pentanone (C₅H₁₀O).