Stereoisomers which are not mirror image of each other, are called.:

Options

A. Enantiomers
B. Tautomers
C. Meso
D. Diastereomers

Answer

To solve the question "Stereoisomers which are not mirror images of each other, are called:", we will analyze the options provided and determine the correct answer step by step.

### Step 1: Understand the Types of Stereoisomers
Stereoisomers are compounds that have the same molecular formula and connectivity of atoms but differ in the spatial arrangement of those atoms. There are two main types of stereoisomers:
1. **Enantiomers**: These are stereoisomers that are non-superimposable mirror images of each other.
2. **Diastereomers**: These are stereoisomers that are not mirror images of each other.

### Step 2: Analyze the Options
Let's look at the options provided in the question:

1. **Enantiomers**: As defined, enantiomers are mirror images of each other. Therefore, this option cannot be correct since we are looking for stereoisomers that are not mirror images.

2. **Tautomers**: Tautomers are a type of structural isomerism, not stereoisomerism. They involve the shifting of protons and electrons within a molecule, leading to different structural forms. Thus, this option is also incorrect.

3. **Mesocompounds**: Mesocompounds are a specific type of stereoisomer that has multiple stereogenic centers but is superimposable on its mirror image, making it achiral. Therefore, this option does not fit our requirement either.

4. **Diastereomers**: Diastereomers are stereoisomers that are not mirror images of each other. They can have different physical and chemical properties. This option fits our requirement perfectly.

### Step 3: Conclusion
Based on the analysis of the options, the correct answer to the question is:

**Diastereomers**