Which of the following is least reactive in a nucleophilic substiution reaction

Options

A. `CH_(2)=CHCI`
B. `CH_(3)CH_(2)CI`
C. `CH_(2)=CHCH_(2)CI`s
D. `(CH_(3))_(3)C-CI`

Answer

To determine which compound is least reactive in a nucleophilic substitution reaction among the given options (Vinyl Chloride, Ethyl Chloride, Allyl Chloride, and Tert-Butyl Chloride), we need to analyze the stability of the resulting carbocations formed after the departure of the leaving group (Cl).

### Step 1: Understand Nucleophilic Substitution Reactions
Nucleophilic substitution reactions involve the replacement of a leaving group (in this case, Cl) by a nucleophile. The reactivity of the alkyl halide in these reactions is influenced by the stability of the carbocation that forms after the leaving group departs.

**Hint:** Remember that the stability of the carbocation is crucial for the reactivity in nucleophilic substitution reactions.

### Step 2: Analyze Each Compound
1. **Ethyl Chloride (CH3CH2Cl)**:
- Upon losing Cl, it forms an ethyl carbocation (CH3CH2+), which is a primary carbocation. Primary carbocations are less stable compared to secondary and tertiary carbocations.

2. **Tert-Butyl Chloride ((CH3)3CCl)**:
- This compound forms a tert-butyl carbocation ((CH3)3C+), which is a tertiary carbocation. Tertiary carbocations are very stable due to hyperconjugation and inductive effects from the surrounding alkyl groups.

3. **Allyl Chloride (CH2=CH-CH2Cl)**:
- When Cl is removed, it forms an allyl carbocation (CH2=CH-CH2+). This carbocation is resonance-stabilized because the positive charge can be delocalized over the double bond, making it more stable than a primary carbocation.

4. **Vinyl Chloride (CH2=CHCl)**:
- Upon losing Cl, it forms a vinyl carbocation (CH2=CH+). This carbocation is also resonance-stabilized, but the carbon-chlorine bond has a partial double bond character due to the presence of the double bond. This makes the bond stronger and more difficult to break, leading to lower reactivity.

**Hint:** Compare the stability of the carbocations formed from each compound to determine which one is least reactive.

### Step 3: Compare Reactivity
- **Tert-Butyl Chloride** is the most reactive due to the stability of the tertiary carbocation.
- **Allyl Chloride** is also reactive due to resonance stabilization.
- **Ethyl Chloride** is less reactive than allyl and tert-butyl chlorides because it forms a primary carbocation.
- **Vinyl Chloride** is the least reactive because the carbon-chlorine bond has partial double bond character, making it harder for the bond to break.

### Conclusion
Based on the analysis, **Vinyl Chloride** is the least reactive in a nucleophilic substitution reaction due to the stability of the resulting carbocation and the strength of the carbon-chlorine bond.

**Final Answer:** Option A: Vinyl Chloride is least reactive in nucleophilic substitution reactions.