Identify Z in the following reaction :
`2H_(3)C COCH_(3) underset(ii.Delta, H^(+))overset(i.Ba(OH)_(2))to Z`

Options

A. `H_(3)C CH_(2)CO_(2)H`
B. `2H_(3)C CO_(2)H`
C. `H_(3)C COCH_(2)CO_(2)H`
D. `H_(3)C-underset(CH_(3))underset(|)C=CHCOCH_(3)`

Answer

To identify Z in the given reaction involving acetone (2H₃C COCH₃), we will go through the steps of the reaction systematically.

### Step-by-Step Solution:

1. **Identify the Reactants:**
The reactants are two moles of acetone, which has the structure CH₃C(=O)CH₃.

2. **First Step - Reaction with Ba(OH)₂:**
In the first step, we treat the acetone with barium hydroxide (Ba(OH)₂). The hydroxide ion (OH⁻) from Ba(OH)₂ acts as a base and abstracts a proton (H⁺) from one of the methyl groups (CH₃) of acetone. This results in the formation of an enolate ion:
\[ CH₃C(=O)CH₂⁻ \]

3. **Nucleophilic Attack:**
The enolate ion formed in the previous step acts as a nucleophile and attacks the carbonyl carbon of another acetone molecule. This leads to the formation of a β-hydroxy ketone:
\[ CH₃C(=O)CH₂C(OH)(CH₃)₂ \]

4. **Second Step - Protonation and Heating:**
In the second step, we add an acid (H⁺) and heat the reaction mixture. The negative charge on the oxygen of the β-hydroxy ketone is protonated, resulting in a hydroxyl group. Upon heating, a water molecule is eliminated, leading to the formation of an α,β-unsaturated ketone:
\[ CH₃C(=O)CH=CH₂ \]

5. **Final Product - Identify Z:**
The final product, which is Z, is an α,β-unsaturated ketone. The structure can be represented as:
\[ CH₃C(=O)CH=CH₂ \]
This compound is known as 4-methylpent-3-en-2-one.

### Conclusion:
Thus, Z in the reaction is an α,β-unsaturated ketone, specifically 4-methylpent-3-en-2-one.