`SN^(2)` reaction is a bimolecular reaction which takes places by the formation of `T.S.` Veolcity of the reaction depends on the concentration of the substrate as well as the nucleophile.
The reaction is favoureed by strong `Nu^(o-)` and in the presence of polar aprotic sovlent, optically active halides give. Walken inversion by `SN^(2)` mechanism. The presence of hero group (atom) at `beta-C` atom, unsaturation at `beta-C` and `(-overset(O)overset(||)(C)-)` group at `alpha-C` atomn favor `SN^(2)` mechanism.
Allyl halides and benzyl halides give `SN^(1)` and `SN^(2)` reactions. Allyl halides alos give `SN^(2)` mechanism `EDG` at ortho- and para- postions in benzyl halides favors `SN^(1)` mechanism, wheras `EWG` favors `SN^(2)` mechanism.
Which of the following will give Walden inversion ?

Options

A. `C_(4)H_(9) - CHD - Br`,
B.
C.
D. All

Explanation

To determine which of the given compounds will give Walden inversion, we need to analyze the conditions for an SN2 reaction and the presence of a chiral center. Here’s a step-by-step solution:

### Step 1: Understand Walden Inversion
Walden inversion refers to the inversion of configuration at a chiral center during a chemical reaction, specifically in the context of SN2 reactions. In SN2 reactions, a nucleophile attacks the electrophilic carbon, leading to the inversion of the stereochemistry at that carbon.

**Hint:** Remember that Walden inversion occurs at a chiral center during an SN2 reaction.

### Step 2: Identify Chiral Centers
A chiral center is typically a carbon atom that has four different substituents attached to it. To find out if a compound can undergo Walden inversion, we need to identify if it has a chiral carbon.

**Hint:** Look for carbon atoms that have four different groups attached to them to identify chiral centers.

### Step 3: Analyze Each Compound
- **Compound A:** Check if it has a chiral center. If it has a carbon with four different groups, it is chiral. Since it is also a primary alkyl halide, it can undergo an SN2 reaction, leading to Walden inversion.

- **Compound B:** Check for a chiral center. If this compound has two identical groups (like two hydrogens) on the carbon, it is not chiral and cannot lead to Walden inversion, even if it can undergo SN2.

- **Compound C:** Similar to Compound B, if it has two identical groups on the carbon, it is not chiral and cannot undergo Walden inversion.

**Hint:** For each compound, determine if it has a chiral center and if it is capable of undergoing an SN2 reaction.

### Step 4: Conclusion
After analyzing the compounds:
- **Compound A** has a chiral center and can undergo an SN2 reaction, thus it will lead to Walden inversion.
- **Compound B** and **Compound C** do not have chiral centers, so they cannot undergo Walden inversion.

**Final Answer:** The compound that will give Walden inversion is **Option A**.