Polyvinyl alcohol is an important polymer. The structure is given below
`(-CH_(2)-underset(OH)underset("| ")"CH"-CH_(2)-underset(OH)underset("| ")"CH"-CH_(2)-underset(OH)underset("| ")"CH"-)`
It is prepared by polymerization of

Options

A. `CH_(2)=CH-OH`
B. `CH_(2)=CH-OCOCH_(3)`, followed by hydrolysis
C. `CH_(2)=CH-CN`, followed by hydrolysis
D. `CH_(2)=CH-COOCH_(3)`, followed by hydrolysis

Answer

To determine the monomer from which polyvinyl alcohol is prepared, we need to analyze the structure of polyvinyl alcohol and identify the corresponding monomeric unit.

### Step-by-Step Solution:

1. **Identify the Structure of Polyvinyl Alcohol**:
The structure of polyvinyl alcohol consists of repeating units that include hydroxyl (–OH) groups attached to a carbon chain. The given structure can be represented as:
\[ (-CH_2-CHOH-CH-CHOH-CH-CHOH-CH-) \]
This indicates that each repeating unit contains a vinyl group (–CH=CH2) that has undergone polymerization.

2. **Determine the Monomer**:
The repeating unit in polyvinyl alcohol suggests that it is derived from a monomer that has a double bond and can form a hydroxyl group upon polymerization. The most likely candidate for this is vinyl alcohol, which has the structure:
\[ CH_2=CHOH \]
This monomer can polymerize to form the polymer structure of polyvinyl alcohol.

3. **Polymerization Process**:
The polymerization of vinyl alcohol occurs through an addition reaction, where the double bond in vinyl alcohol opens up to form long chains. The reaction can be summarized as:
\[ n \, CH_2=CHOH \rightarrow [-CH_2-CHOH-]_n \]
where \( n \) is the number of repeating units.

4. **Conclusion**:
Therefore, polyvinyl alcohol is prepared by the polymerization of vinyl alcohol (CH2=CHOH).

### Final Answer:
Polyvinyl alcohol is prepared by the polymerization of **vinyl alcohol (CH2=CHOH)**.

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