`CH_(3)-CHCl-CH-CH_(3)` has a chiral centre. Which one of the following represent its `R`-configuration?

Options

A. `H-underset(C_(2)H_(5))underset(|)overset(CH_(3))overset(|)C-Cl`
B. `H_(3)C-underset(H)underset(|)overset(C_(2)H_(5))overset(|)(C)-Cl`
C. `H-underset(Cl)underset(|)overset(C_(2)H_(5))overset(|)C-CH_(3)`
D. `Cl-underset(H)underset(|)overset(C_(2)H_(5))overset(|)C-CH_(3)`

Answer

To determine the R-configuration of the chiral center in the molecule \( CH_3-CHCl-CH-CH_3 \), we will follow these steps:

### Step 1: Identify the Chiral Center
The chiral center in the molecule is the carbon atom that is attached to four different groups. In this case, the carbon attached to the chlorine (Cl) is the chiral center.

### Step 2: Assign Priorities to the Groups
Using the Cahn-Ingold-Prelog (CIP) priority rules, we will assign priorities to the four groups attached to the chiral center based on atomic number:
1. **Chlorine (Cl)** - highest priority (atomic number 17)
2. **Ethyl group (C2H5)** - second priority (carbon has a higher atomic number than hydrogen)
3. **Methyl group (CH3)** - third priority (carbon has a higher atomic number than hydrogen)
4. **Hydrogen (H)** - lowest priority (atomic number 1)

### Step 3: Arrange the Groups
Now, we will visualize the molecule with the groups arranged according to their priority:
- 1: Cl
- 2: C2H5
- 3: CH3
- 4: H

### Step 4: Determine the Orientation
To determine the configuration, we need to orient the molecule so that the lowest priority group (H) is in the back. We will then observe the order of the remaining groups (1, 2, and 3):
- If the order of the groups 1 → 2 → 3 is clockwise, the configuration is R.
- If the order is counterclockwise, the configuration is S.

### Step 5: Analyze the Arrangement
In this case, if we look at the arrangement:
- From Cl (1) to C2H5 (2) to CH3 (3), the order is clockwise.

### Step 6: Conclusion
Since the order of priority (1, 2, 3) is clockwise, the configuration of the chiral center is R.

### Final Answer
The correct representation of the R-configuration of the molecule \( CH_3-CHCl-CH-CH_3 \) is the option that corresponds to this arrangement.

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