`(CH_(3))_(2)CHI overset(KOH)underset(EtOH)rarr A overset(SO_(2)Cl_(2))underset(475 K)rarr B`
The compound B in the sequence is

Options

A. Dimethyl sulphate
B. `1,2--` Dichloro ethane
C. `3-` Chloro propene
D. `1-` Chloro`-2-` iosopropane

Explanation

To solve the given question, we will break down the reaction sequence step by step.

### Step 1: Identify the Starting Compound
The starting compound is (CH₃)₂CHI, which is 2-iodopropane. This compound has three carbon atoms and is a secondary alkyl halide.

### Step 2: Reaction with KOH in Ethanol
When 2-iodopropane reacts with alcoholic KOH (KOH in ethanol), it undergoes an elimination reaction (dehydrohalogenation). In this reaction, the iodine atom (I) and a hydrogen atom (H) from the adjacent carbon are removed, leading to the formation of an alkene.

- **Elimination Reaction**:
- The H atom is removed from the carbon adjacent to the carbon bearing the iodine.
- The I atom is removed from the carbon that has it.

This results in the formation of propene (C₃H₆), which has the structure:

\[ \text{CH}_2=CH-CH_3 \]

### Step 3: Identify the Product A
The product formed from the first reaction is propene (C₃H₆). We will denote this compound as A.

### Step 4: Reaction with SO₂Cl₂
Next, propene (A) reacts with sulfur dichloride (SO₂Cl₂) at elevated temperature (475 K). This reaction involves the halogenation of the allylic carbon, which is the carbon adjacent to the double bond.

- **Halogenation**:
- The chlorine atom from SO₂Cl₂ will add to the allylic carbon (the carbon adjacent to the double-bonded carbon).

In propene, the allylic carbon is the one next to the double bond. Therefore, the chlorine will substitute for a hydrogen atom on this carbon.

### Step 5: Identify the Product B
The final product formed from the reaction of propene with SO₂Cl₂ is 3-chloropropene. The structure of 3-chloropropene is:

\[ \text{CH}_2=CH-CH_2Cl \]

### Conclusion
Thus, the compound B in the sequence is **3-chloropropene**.

### Summary of Steps:
1. Identify the starting compound (2-iodopropane).
2. React with alcoholic KOH to form propene (A).
3. React propene with SO₂Cl₂ to form 3-chloropropene (B).