Which of the following is chiral?

Options

A.
B.
C.
D.

Explanation

To determine which of the given options is chiral, we need to follow these steps:

### Step 1: Understand the Definition of Chirality
A chiral molecule is one that cannot be superimposed on its mirror image. A chiral center (often a carbon atom) must have four different substituents (or groups) attached to it, and it should not have any double bonds.

### Step 2: Analyze Each Option
We will analyze each option to see if it contains a chiral center.

#### Option 1:
- **Molecule:** Contains phosphorus.
- **Analysis:** Phosphorus is bonded to four different groups, but it has a double bond with oxygen. Since it has a double bond, it cannot be considered chiral.

#### Option 2:
- **Molecule:** Contains sulfur.
- **Analysis:** Sulfur is bonded to four different groups, but it also has a double bond with oxygen. Thus, it cannot be considered chiral.

#### Option 3:
- **Molecule:** Contains nitrogen.
- **Analysis:** Nitrogen is bonded to four different groups: methyl, ethyl, phenyl, and hydrogen. There are no double bonds present, so this molecule can be considered chiral.

#### Option 4:
- **Molecule:** Contains sulfur.
- **Analysis:** In this case, sulfur is bonded to two identical groups. Since two groups are the same, this cannot be a chiral center.

### Step 3: Conclusion
After analyzing all the options, we find that **Option 3**, which contains nitrogen with four different substituents and no double bonds, is the only chiral molecule.

### Final Answer:
**The chiral molecule is Option 3.**

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