Which of following compounds exists as non-resolvable racemic mixture?

Options

A.
B.
C.
D.

Explanation

To determine which of the given compounds exists as a non-resolvable racemic mixture, we need to analyze each compound for optical activity. A compound is optically active if it has a chiral center and lacks symmetry. Here’s a step-by-step solution:

### Step 1: Understand the Criteria for Optical Activity
- A compound must have a chiral center (a carbon atom bonded to four different groups) or a chiral nitrogen (in the case of amines) to be optically active.
- The compound should not possess any plane of symmetry.

**Hint:** Look for chiral centers or chiral nitrogen atoms in the compounds.

### Step 2: Analyze Each Compound
1. **First Compound:**
- Check the nitrogen atom: It has two hydrogen atoms attached.
- Since there are two identical groups (hydrogens), this nitrogen is not chiral.
- **Conclusion:** This compound is not optically active and thus not a non-resolvable racemic mixture.

**Hint:** Identify if the nitrogen has all different groups attached.

2. **Second Compound:**
- Check the nitrogen atom: It has an ethyl group, a different group (let's say a propyl group), and a hydrogen.
- All three groups attached to the nitrogen are different.
- **Conclusion:** This compound is optically active and can exist as a non-resolvable racemic mixture.

**Hint:** Ensure all groups attached to the chiral center are unique.

3. **Third Compound:**
- Check the nitrogen atom: It has two hydrogen atoms attached.
- Similar to the first compound, the presence of two identical groups means it is not chiral.
- **Conclusion:** This compound is not optically active and thus not a non-resolvable racemic mixture.

**Hint:** Look for identical groups attached to the chiral center.

4. **Fourth Compound:**
- Check the nitrogen atom: It has a methyl group, an ethyl group, and a hydrogen.
- All three groups attached to the nitrogen are different.
- **Conclusion:** This compound is optically active and can exist as a non-resolvable racemic mixture.

**Hint:** Confirm that the nitrogen has three distinct groups.

### Step 3: Final Conclusion
Based on the analysis:
- The second and fourth compounds are the ones that can exist as non-resolvable racemic mixtures due to their optical activity.

**Final Answer:** The second and fourth compounds exist as non-resolvable racemic mixtures.