The number of isomers for the compound with molecule formula `C_2HDFCl` is :

Explanation

To determine the number of isomers for the compound with the molecular formula C₂HDFCl, we will follow these steps:

### Step 1: Identify the Structure
The compound C₂HDFCl consists of two carbon atoms, one hydrogen atom, one deuterium atom (D), one fluorine atom (F), and one chlorine atom (Cl). The two carbon atoms are connected by a double bond (C=C).

### Step 2: Draw the Basic Structure
We can start by drawing the basic structure of the compound:
```
H F
\ /
C=C
/ \
D Cl
```
In this structure, we have one carbon atom with a hydrogen (H) and fluorine (F) attached, and the other carbon atom with a deuterium (D) and chlorine (Cl) attached.

### Step 3: Identify Possible Isomers
Now we will identify the possible isomers by changing the positions of the substituents (H, D, F, Cl) on the carbon atoms.

1. **Isomer 1**: H on one carbon, D on the other, F and Cl on the same carbons as shown above.
2. **Isomer 2**: H on one carbon, F on the other, D and Cl on the same carbons.
3. **Isomer 3**: D on one carbon, Cl on the other, H and F on the same carbons.
4. **Isomer 4**: F on one carbon, Cl on the other, H and D on the same carbons.
5. **Isomer 5**: H and F on one carbon, D and Cl on the other carbon.
6. **Isomer 6**: D and F on one carbon, H and Cl on the other carbon.

### Step 4: Count Unique Isomers
After drawing and considering the different arrangements, we can see that we have 6 unique isomers.

### Conclusion
The total number of isomers for the compound C₂HDFCl is **6**.

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