How many stereoisomers can be drawn for the following molecule?
`H_(3)"CCH"_(2)CH=CHCH_(2)CH(Cl)CH_(3)`

Answer

To determine the number of stereoisomers for the molecule `H₃C-CH₂-CH=CH-CH₂-CH(Cl)-CH₃`, we will follow these steps:

### Step 1: Identify the Structure
The given molecule can be represented structurally as follows:
```
H H H H
| | | |
H₃C-C-C=C-C-CH(Cl)-CH₃
| | |
H H H
```
This molecule contains a double bond and a chiral center.

### Step 2: Identify Chiral Centers
A chiral center is a carbon atom that has four different substituents. In this molecule, we can identify the following:
- The carbon attached to the chlorine (C(Cl)) is a chiral center because it is bonded to four different groups (H, Cl, CH₂, and CH₃).
- The carbon involved in the double bond (C=C) can also exhibit geometrical isomerism (cis/trans) but is not a chiral center.

### Step 3: Count the Chiral Centers
In this molecule, there is **1 chiral center** (the carbon with the chlorine).

### Step 4: Determine the Number of Stereoisomers
The formula for calculating the number of stereoisomers based on the number of chiral centers (n) is:
\[ \text{Number of stereoisomers} = 2^n \]
Since we have 1 chiral center:
\[ \text{Number of stereoisomers} = 2^1 = 2 \]

### Step 5: Consider Geometrical Isomerism
The double bond in the molecule can also lead to geometrical isomers (cis and trans). For the double bond, we can have:
- **Cis isomer**: where the higher priority groups are on the same side.
- **Trans isomer**: where the higher priority groups are on opposite sides.

Thus, for the double bond, we have **2 geometrical isomers**.

### Step 6: Combine the Stereoisomers
Now, we combine the stereoisomers from the chiral center and the geometrical isomers:
- From the chiral center: 2 optical isomers (R and S forms).
- From the double bond: 2 geometrical isomers (cis and trans).

### Final Calculation
The total number of stereoisomers is:
\[ \text{Total stereoisomers} = \text{Optical isomers} \times \text{Geometrical isomers} = 2 \times 2 = 4 \]

### Conclusion
The total number of stereoisomers for the molecule `H₃C-CH₂-CH=CH-CH₂-CH(Cl)-CH₃` is **4**.

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