Propyne is formed by heating 1,2-dibromopropane with -

Options

A. `C_(2)H_(5)ONa`
B. Alc. KOH and sodamide
C. Aqueous alkali
D. Sodalime

Answer

To form propyne from 1,2-dibromopropane, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Structure of 1,2-Dibromopropane**:
- 1,2-Dibromopropane has the structure:
\[ CH_2Br-CHBr-CH_3 \]
- This structure consists of three carbon atoms (propane) with two bromine atoms attached to the first and second carbon.

2. **Understand the Elimination Reaction**:
- To convert 1,2-dibromopropane to propyne, we need to perform an elimination reaction where two bromine atoms (Br) and two hydrogen atoms (H) are removed to form a triple bond between the first and second carbon atoms.

3. **Choose the Correct Reagent**:
- The reaction requires a strong base to facilitate the elimination of HBr. Suitable reagents include:
- Alcoholic KOH (potassium hydroxide)
- Soda lime (a mixture of NaOH and CaO)
- These reagents promote the elimination reaction, leading to the formation of a triple bond.

4. **Perform the Reaction**:
- When heating 1,2-dibromopropane with alcoholic KOH or soda lime, the following elimination occurs:
- The first bromine (from the first carbon) and a hydrogen (from the second carbon) are eliminated, forming a double bond.
- Then, the second bromine (from the second carbon) and another hydrogen (from the first carbon) are eliminated, forming a triple bond.
- The resulting structure will be:
\[ CH \equiv C - CH_3 \]
- This structure represents propyne.

5. **Final Product**:
- The final product of the reaction is propyne, which is represented as:
\[ CH_3C \equiv CH \]