Complete the following reaction:
`CH_(3)CH_(2)COOHoverset(P,Br_(2))to[A]underset((ii)H^(+))overset((i)alc. KOH("excess"))to[B]`

Explanation

To complete the reaction given in the question, we will follow these steps:

### Step 1: Reaction of Propionic Acid with Red Phosphorus and Bromine
- **Starting Material**: Propionic acid (CH₃CH₂COOH)
- **Reagents**: Red phosphorus (P) and bromine (Br₂)
- **Process**: The reaction involves the halogenation of the alpha carbon of propionic acid. The bromine replaces one of the alpha hydrogens (the hydrogen on the carbon adjacent to the carboxylic acid group).
- **Product**: The product of this step is alpha-bromopropanoic acid (CH₃CHBrCOOH).

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