How many structural isomeric ketones having molecular formula `(C_(5)H_(10)O)` give iodoform test?

Options

A. 1
B. 2
C. 3
D. 4

Explanation

To determine how many structural isomeric ketones with the molecular formula \( C_5H_{10}O \) give a positive iodoform test, we can follow these steps:

### Step 1: Understand the Iodoform Test
The iodoform test is positive for compounds that have a methyl ketone group (i.e., a ketone with the structure \( RCOCH_3 \)) or for secondary alcohols that can be oxidized to form such ketones.

### Step 2: Identify Possible Ketones
We need to find the structural isomers of ketones with the formula \( C_5H_{10}O \). The general structure of a ketone is \( R_1CO R_2 \).

### Step 3: List Structural Isomers
1. **3-Pentanone**: \( CH_3CH_2COCH_2CH_3 \) - This is a methyl ketone and will give a positive iodoform test.
2. **2-Pentanone**: \( CH_3COCH_2CH_2CH_3 \) - This is also a methyl ketone and will give a positive iodoform test.
3. **4-Methyl-2-pentanone**: \( CH_3C(CH_3)COCH_2CH_3 \) - This is another methyl ketone and will give a positive iodoform test.
4. **3-Methyl-3-butanone**: \( (CH_3)_2C(=O)CH_2CH_3 \) - This is also a methyl ketone and will give a positive iodoform test.

### Step 4: Count the Isomers
From the above analysis, we find that:
- 3-Pentanone
- 2-Pentanone
- 4-Methyl-2-pentanone
- 3-Methyl-3-butanone

All four of these ketones give a positive iodoform test.

### Conclusion
Thus, the total number of structural isomeric ketones with the molecular formula \( C_5H_{10}O \) that give a positive iodoform test is **4**.

---