The reaction shows which of the following mechanisms?
`CH_(3) - underset(CH_(3))underset(|)CH - Cl overset("KOH"(aq))(rarr) CH_(3) - underset(CH_(3))underset(|)(CH)-OH + Cl^(-)`

Options

A. `S_(E)`2
B. `S_(N)`2 only
C. `E_(2)`
D. `S_(N)^(2)` majorly

Answer

To determine the mechanism of the given reaction, we will analyze the reactants, the conditions under which the reaction occurs, and the nature of the nucleophile involved.

### Step-by-Step Solution:

1. **Identify the Reactants and Products:**
The reactant is a haloalkane (specifically, a secondary haloalkane due to the presence of a carbon bonded to two other carbon atoms) and the product is an alcohol. The reaction is as follows:
\[ CH_3 - CH(CH_3) - Cl + KOH(aq) \rightarrow CH_3 - CH(CH_3) - OH + Cl^- \]

2. **Identify the Reaction Conditions:**
The reaction is carried out in the presence of aqueous KOH. This means that KOH is dissolved in water, which dissociates to provide hydroxide ions (OH⁻) as the nucleophile.

3. **Understand the Nature of the Nucleophile:**
In aqueous KOH, OH⁻ is a strong nucleophile. Strong nucleophiles favor bimolecular nucleophilic substitution (SN2) mechanisms, especially when the substrate is a secondary haloalkane.

4. **Consider the Mechanism:**
For a secondary haloalkane, two mechanisms could potentially occur:
- **SN2 Mechanism:** In this mechanism, the nucleophile attacks the carbon atom from the opposite side of the leaving group (Cl), resulting in a concerted reaction where the bond formation and bond breaking occur simultaneously.
- **SN1 Mechanism:** This mechanism involves the formation of a carbocation intermediate after the leaving group departs. However, this is less favored in the presence of a strong nucleophile like OH⁻.

5. **Determine the Likely Mechanism:**
Given that:
- The substrate is a secondary haloalkane.
- Aqueous KOH provides a strong nucleophile (OH⁻).
- SN2 reactions are favored with strong nucleophiles and secondary substrates.

The reaction is most likely to proceed via the **SN2 mechanism**. However, it is also possible for the SN1 mechanism to occur, but the probability is significantly lower.

### Conclusion:
Thus, the reaction predominantly follows the **SN2 mechanism**.

---