Identify B in the following sequence,
`CH_(3)CH_(2)CH_(2)OHoverset(PCl_(3))rarrAoverset("alc.KOH")rarrB` :

Options

A. Propyne
B. Propene
C. Propanol
D. Propanone

Explanation

To identify compound B in the given sequence, we will analyze the reactions step by step.

### Step 1: Identify the starting compound
The starting compound is **CH₃CH₂CH₂OH**, which is known as **1-propanol** or **n-propanol**.

### Step 2: Reaction with PCl₃
When 1-propanol reacts with phosphorus trichloride (PCl₃), it undergoes a substitution reaction. In this reaction, the hydroxyl group (-OH) is replaced by a chlorine atom (-Cl).

The reaction can be represented as:
\[ \text{CH}_3\text{CH}_2\text{CH}_2\text{OH} + \text{PCl}_3 \rightarrow \text{CH}_3\text{CH}_2\text{CH}_2\text{Cl} + \text{HCl} + \text{H}_3\text{PO}_3 \]

The product formed here is **1-chloropropane** (A).

### Step 3: Reaction with alcoholic KOH
Next, 1-chloropropane (A) reacts with alcoholic potassium hydroxide (KOH). In this reaction, KOH acts as a base and facilitates a dehydrohalogenation reaction. This means that it will abstract a hydrogen atom (H) from the carbon adjacent to the carbon bonded to chlorine, leading to the elimination of HCl.

The reaction can be represented as:
\[ \text{CH}_3\text{CH}_2\text{CH}_2\text{Cl} + \text{alc. KOH} \rightarrow \text{CH}_3\text{CH}=\text{CH}_2 + \text{HCl} + \text{KCl} \]

The product formed from this reaction is **propene** (B), which is an alkene.

### Conclusion
Thus, the final product B is **propene**.

### Summary of Steps:
1. Identify the starting compound (1-propanol).
2. React with PCl₃ to form 1-chloropropane (A).
3. React A with alcoholic KOH to form propene (B).