Dehydrohalogenation and acidcatalyzed dehydration reactions are frequently used to propare alkenes from corresponding alkylhalides and alcohols . Out of the given substrates which can be used to prepare styrene ?

Options

A.
B.
C.
D.

Answer

To determine which substrates can be used to prepare styrene (C6H5-CH=CH2) through dehydrohalogenation and acid-catalyzed dehydration reactions, we will analyze each substrate step by step.

### Step 1: Understand the Reaction Mechanisms
- **Dehydrohalogenation**: This is the elimination of a hydrogen halide (HX) from an alkyl halide, resulting in the formation of an alkene. The reaction typically requires a strong base (like alcoholic KOH).
- **Acid-catalyzed dehydration**: This involves the removal of water from an alcohol in the presence of an acid, leading to the formation of an alkene.

### Step 2: Identify Styrene
Styrene has the structure CH2=CH-C6H5. We need to check if the given substrates can lead to this structure through the aforementioned reactions.

### Step 3: Analyze Each Substrate

#### Substrate A: Alkyl Halide
1. **Reaction with Alcoholic KOH**:
- The strong base (OH-) will abstract a proton from the alkyl halide.
- The halogen will leave, resulting in the formation of a double bond.
- **Product**: CH2=CH-C6H5 (Styrene).
2. **Conclusion**: Substrate A can be used to prepare styrene.

#### Substrate B: Alcohol
1. **Reaction with Acid**:
- The alcohol will be protonated by the acid.
- Water will be eliminated, forming a carbocation.
- A proton will be abstracted, leading to the formation of a double bond.
- **Product**: CH2=CH-C6H5 (Styrene).
2. **Conclusion**: Substrate B can also be used to prepare styrene.

#### Substrate C: Alkyl Halide
1. **Reaction with Alcoholic KOH**:
- The strong base will abstract a proton.
- The halogen will leave, but the structure may lead to a different alkene.
- **Product**: A different alkene (not styrene).
2. **Conclusion**: Substrate C cannot be used to prepare styrene.

#### Substrate D: Alkyl Halide
1. **Reaction with Alcoholic KOH**:
- The strong base will abstract a proton.
- The halogen will leave, resulting in a double bond.
- **Product**: CH2=CH-C6H5 (Styrene).
2. **Conclusion**: Substrate D can be used to prepare styrene.

### Final Conclusion
The substrates that can be used to prepare styrene through dehydrohalogenation and acid-catalyzed dehydration are:
- **Substrate A**
- **Substrate B**
- **Substrate D**

### Summary of Answers
- **Correct Answers**: A, B, and D can be used to prepare styrene.

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