which of the following statement is correct for the reactivity in `S_(N)2` reaction ?

Options

A.
B.
C.
D. is more reactive than

Answer

To determine the correct statement regarding the reactivity in \( S_N2 \) reactions, let’s analyze the factors that influence the reactivity of alkyl halides in these reactions step by step.

### Step 1: Understanding \( S_N2 \) Mechanism
The \( S_N2 \) reaction is a bimolecular nucleophilic substitution reaction where the nucleophile attacks the electrophilic carbon atom from the opposite side of the leaving group. This results in an inversion of configuration at the carbon center.

**Hint:** Remember that \( S_N2 \) reactions involve a backside attack by the nucleophile.

### Step 2: Role of Nucleophile
The strength of the nucleophile is crucial for \( S_N2 \) reactions. A strong nucleophile will effectively attack the electrophilic carbon. The nucleophile should be electron-rich and capable of forming a bond with the carbon atom.

**Hint:** Strong nucleophiles enhance the reactivity in \( S_N2 \) reactions.

### Step 3: Leaving Group Ability
The leaving group must be a good leaving group, meaning it should be able to depart easily from the carbon atom. Good leaving groups are typically weak bases, which can stabilize the negative charge after leaving.

**Hint:** The weaker the bond between the carbon and the leaving group, the better the leaving group.

### Step 4: Steric Hindrance
Steric hindrance around the carbon atom affects the reactivity in \( S_N2 \) reactions. The less steric hindrance there is, the more reactive the alkyl halide will be. Methyl halides are the most reactive due to minimal steric hindrance, followed by primary, secondary, and tertiary alkyl halides, which have increasing steric hindrance.

**Hint:** Methyl halides are the most reactive in \( S_N2 \) due to less steric hindrance.

### Step 5: Reactivity Order
The general order of reactivity for alkyl halides in \( S_N2 \) reactions is:
1. Methyl halides (most reactive)
2. Primary alkyl halides
3. Secondary alkyl halides
4. Tertiary alkyl halides (least reactive)

**Hint:** Remember the reactivity decreases as the number of alkyl groups attached to the carbon increases.

### Step 6: Considering Hybridization
The hybridization of the carbon atom also plays a role. Carbon atoms with higher \( s \)-character (like \( sp^2 \) or \( sp \)) are more electronegative and can stabilize the positive charge better, making them less favorable for \( S_N2 \) reactions compared to \( sp^3 \) hybridized carbons.

**Hint:** \( sp^3 \) hybridized carbons are more favorable for \( S_N2 \) reactions.

### Conclusion
Based on the analysis, the correct statement regarding the reactivity in \( S_N2 \) reactions is that methyl halides are the most reactive, followed by primary, secondary, and tertiary alkyl halides. The factors influencing reactivity include the strength of the nucleophile, the ability of the leaving group, and steric hindrance.

**Final Answer:** The correct statement for the reactivity in \( S_N2 \) reaction is that methyl halides are the most reactive due to less steric hindrance and a good leaving group.