Ethyl acetoacetate shows -

Options

A. Enantiomorphism
B. Geometrical isomerism
C. Diastereoisomerism
D. Keto-enol tautomerism

Answer

To determine the types of isomerism exhibited by ethyl acetoacetate, we can follow these steps:

### Step 1: Draw the Structure of Ethyl Acetoacetate
Ethyl acetoacetate has the following structure:
- It consists of a carbon chain with a carbonyl (C=O) group and an ester functional group.
- The structure can be represented as:

```
CH3-C(=O)-CH2-C(=O)-O-CH2-CH3
```

### Step 2: Identify Chiral Centers
- A chiral center is a carbon atom that is attached to four different groups.
- In the structure of ethyl acetoacetate, we can see that there are no carbon atoms that are bonded to four different substituents.
- Therefore, there are no chiral centers in ethyl acetoacetate.

### Step 3: Check for Optical Isomerism (Enantiomers)
- Since there are no chiral centers, ethyl acetoacetate cannot exhibit optical isomerism (enantiomers).
- Thus, it does not show enantiomerism.

### Step 4: Check for Geometrical Isomerism
- Geometrical isomers (cis/trans or E/Z isomerism) occur due to restricted rotation around a double bond or a ring structure.
- In ethyl acetoacetate, there are no such restrictions in the carbon chain that would lead to geometrical isomerism.
- Therefore, it does not show geometrical isomerism.

### Step 5: Check for Diastereomers
- Diastereomers are stereoisomers that are not mirror images of each other.
- Since ethyl acetoacetate does not have optical isomers (due to the absence of chiral centers) or geometrical isomers, it cannot have diastereomers either.

### Step 6: Check for Tautomerism
- Tautomerism is a special type of isomerism involving the migration of a hydrogen atom and a shift of a double bond.
- Ethyl acetoacetate can exist in two forms: the keto form and the enol form.
- The keto form is the more stable form, while the enol form can be formed through tautomerization.
- The keto form is represented as:

```
CH3-C(=O)-CH2-C(=O)-O-CH2-CH3
```

- The enol form is represented as:

```
CH3-C(OH)=CH-C(=O)-O-CH2-CH3
```

### Conclusion
Based on the analysis, ethyl acetoacetate shows **keto-enol tautomerism**.

### Summary of Isomerism in Ethyl Acetoacetate:
1. **Optical Isomerism**: No (no chiral centers)
2. **Geometrical Isomerism**: No (no restricted rotation)
3. **Diastereomers**: No (no optical or geometrical isomers)
4. **Tautomerism**: Yes (keto-enol tautomerism)