`CH_(3)CH(OH)COOH` molecule shows:

Options

A. geometrical isomerism
B. metamerism
C. optical isomerism
D. tautomerism

Answer

To analyze the molecule \( CH_3CH(OH)COOH \) and determine the types of isomerism it exhibits, we will follow these steps:

### Step 1: Identify the Structure
The molecular formula \( CH_3CH(OH)COOH \) corresponds to lactic acid. The structure can be drawn as follows:
- The first carbon is attached to three hydrogens (methyl group, \( CH_3 \)).
- The second carbon has a hydroxyl group (\( OH \)) and is attached to the first carbon.
- The third carbon is part of the carboxylic acid group (\( COOH \)).

### Step 2: Check for Geometrical Isomerism
Geometrical isomerism requires the presence of a carbon-carbon double bond (C=C) or a carbon with different substituents. In this case, the carbon atoms in lactic acid are all single-bonded (C-C), and the carbon with the hydroxyl group does not have different groups attached to it. Therefore, lactic acid does not exhibit geometrical isomerism.

**Hint:** Geometrical isomerism requires a double bond or a carbon with different substituents.

### Step 3: Check for Metamerism
Metamerism occurs in compounds with the same functional group but different carbon skeletons. Lactic acid has a single carboxylic acid group and does not have two different functional groups on either side of a carbon chain. Therefore, it does not exhibit metamerism.

**Hint:** Metamerism requires bifunctional groups or different carbon skeletons.

### Step 4: Check for Optical Isomerism
Optical isomerism occurs when a molecule has a chiral center, which is a carbon atom bonded to four different groups. In lactic acid, the carbon atom with the hydroxyl group is attached to four different groups: a methyl group (\( CH_3 \)), a hydroxyl group (\( OH \)), a carboxylic acid group (\( COOH \)), and a hydrogen atom (\( H \)). Thus, lactic acid is chiral and exhibits optical isomerism.

**Hint:** Optical isomerism requires a chiral carbon with four different substituents.

### Step 5: Check for Tautomerism
Tautomerism involves the migration of a hydrogen atom and a shift of a double bond. For a compound to exhibit tautomerism, it typically requires a carbonyl group adjacent to an alpha hydrogen. In lactic acid, although there is a carbonyl group in the carboxylic acid, the negative charge that would form upon deprotonation is unstable and does not lead to resonance stabilization. Therefore, lactic acid does not exhibit tautomerism.

**Hint:** Tautomerism requires a stable resonance structure after deprotonation.

### Conclusion
The molecule \( CH_3CH(OH)COOH \) (lactic acid) shows **only optical isomerism** due to the presence of a chiral carbon.

**Final Answer:** The molecule shows optical isomerism.