Identify A and B in the `CH_3CH_2 CH_2Br overset("alc. KOH")to A overset(HBr)toB`.

Explanation

To solve the problem, we will follow the reactions step by step.

### Step 1: Identify the starting compound
The starting compound is **CH₃CH₂CH₂Br**, which is 1-bromopropane.

### Step 2: Reaction with alcoholic KOH
When 1-bromopropane (CH₃CH₂CH₂Br) is treated with alcoholic KOH, it undergoes an elimination reaction (dehydrohalogenation). In this reaction, a hydrogen atom and the bromine atom are removed, resulting in the formation of an alkene.

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