To determine how many different dichlorobutanes can be formed from pure (+) 2-chlorobutane, we can follow these steps:
### Step 1: Understand the Structure of 2-Chlorobutane
2-Chlorobutane is a four-carbon alkane with a chlorine atom attached to the second carbon. The molecular formula for 2-chlorobutane is C4H9Cl.
### Step 2: Identify Possible Chlorination Sites
When chlorination occurs, we can replace hydrogen atoms with chlorine atoms. In 2-chlorobutane, we can chlorinate at different positions, leading to different isomers.
### Step 3: Consider the Different Isomers
1. **1,2-Dichlorobutane**: Chlorine atoms can be added to the first and second carbon.
2. **1,3-Dichlorobutane**: Chlorine atoms can be added to the first and third carbon.
3. **1,4-Dichlorobutane**: Chlorine atoms can be added to the first and fourth carbon.
4. **2,3-Dichlorobutane**: Chlorine atoms can be added to the second and third carbon.
5. **2,4-Dichlorobutane**: Chlorine atoms can be added to the second and fourth carbon.
### Step 4: Analyze Stereoisomers
For some of the dichlorobutane isomers, we can have stereoisomers due to the presence of chiral centers:
- **2,3-Dichlorobutane** has two chiral centers, leading to two stereoisomers.
- The other isomers (1,2-, 1,3-, 1,4-, and 2,4-dichlorobutane) do not have chiral centers or are symmetrical.
### Step 5: Count the Total Isomers
- **1,2-Dichlorobutane**: 1 isomer
- **1,3-Dichlorobutane**: 1 isomer
- **1,4-Dichlorobutane**: 1 isomer
- **2,3-Dichlorobutane**: 2 stereoisomers
- **2,4-Dichlorobutane**: 1 isomer
Adding these together gives us:
1 (1,2) + 1 (1,3) + 1 (1,4) + 2 (2,3) + 1 (2,4) = **5 different dichlorobutanes**.
### Final Answer
Pure (+) 2-chlorobutane gives a total of **5 different dichlorobutanes**.
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