An organic compound `X (C_(4)H_(8)O_(2))` gives positive test with `NaOH` and Phenopthalein. Structure of `X` will be:

Options

A. `CH_(3)-CH_(2)-CH_(2)-underset(O)underset(||)NH_(2)`
B. `CH_(3)-underset(O)underset(||)C-underset(O)underset(||)C-CH_(3)`
C. `CH_(3)-underset(O)underset(||)C-O-C_(2)H_(5)`
D. `CH_(3)-underset(O)underset(||)C-OCH_(3)`

Answer

To determine the structure of the organic compound \( X \) with the molecular formula \( C_4H_8O_2 \) that gives a positive test with sodium hydroxide and phenolphthalein, we can follow these steps:

### Step 1: Analyze the Molecular Formula
The molecular formula \( C_4H_8O_2 \) indicates that the compound contains 4 carbon atoms, 8 hydrogen atoms, and 2 oxygen atoms.

**Hint:** Count the number of carbons, hydrogens, and oxygens to understand the possible functional groups.

### Step 2: Identify Possible Functional Groups
In organic chemistry, two common functional groups that contain two oxygen atoms are carboxylic acids and esters. Carboxylic acids have the structure \( RCOOH \), while esters have the structure \( RCOOR' \).

**Hint:** Recall that carboxylic acids and esters are the primary candidates for compounds with two oxygen atoms.

### Step 3: Determine the Type of Compound
Given that the compound gives a positive test with sodium hydroxide (NaOH), it suggests that the compound is likely a carboxylic acid. This is because carboxylic acids can react with bases like NaOH to form salts and water.

**Hint:** Remember that phenolphthalein is an acid-base indicator that turns colorless in acidic solutions, which aligns with the behavior of carboxylic acids.

### Step 4: Construct the Structure
Let’s construct the structure based on the assumption that \( X \) is a carboxylic acid. We can start with a straight-chain structure:

- The carboxylic acid group will be at one end of the carbon chain.
- A possible structure could be \( CH_3CH_2COOH \) (butyric acid) or \( CH_3C(=O)OCH_2CH_3 \) (an ester).

However, since the positive test with NaOH indicates that it is indeed a carboxylic acid, we will focus on the structure \( CH_3CH_2C(=O)OH \).

**Hint:** Draw the carbon chain and place the carboxylic acid group at one end to satisfy the molecular formula.

### Step 5: Verify the Structure
Now, let’s verify the structure:
- Count the carbons: 4 (correct)
- Count the hydrogens: 8 (correct)
- Count the oxygens: 2 (correct)

Thus, the structure of \( X \) is confirmed to be butanoic acid, \( CH_3CH_2C(=O)OH \).

**Hint:** Always double-check the molecular formula against your drawn structure to ensure accuracy.

### Conclusion
The structure of the organic compound \( X \) is butanoic acid, which can be represented as:

\[ \text{Structure of } X: \quad CH_3CH_2C(=O)OH \]