`beta-`elimination is not possible in

Options

A. `CHCl_3`
B. `(CH_3)_3CBr`
C. `(CH_3)_2CHBr`
D. `(CH_3)_2CHCH_2Br`

Answer

To solve the question regarding the impossibility of beta-elimination in certain compounds, we need to understand the concept of beta-elimination and identify the presence of beta-hydrogens in the given options.

### Step-by-Step Solution:

1. **Understanding Beta-Elimination**:
- Beta-elimination is a reaction where a molecule loses atoms or groups from the beta position (the carbon adjacent to the carbon bearing the leaving group) along with a leaving group. For this reaction to occur, the beta carbon must have at least one hydrogen atom (beta hydrogen) that can be removed.

2. **Analyzing the Options**:
- We need to evaluate each option to check for the presence of beta hydrogens.

3. **Option 1: CHCl3 (Chloroform)**:
- Structure: CHCl3 has one carbon (alpha carbon) attached to three chlorine atoms and one hydrogen atom.
- There is no beta carbon present because there are no adjacent carbons. Therefore, there are no beta hydrogens.
- Conclusion: Beta-elimination is **not possible** in CHCl3.

4. **Option 2: CH3-CHBr-CH3 (Bromoethane)**:
- Structure: This compound has a carbon chain where the central carbon (alpha carbon) is attached to a bromine atom and two methyl groups (CH3).
- The adjacent carbons (beta carbons) have hydrogen atoms. Thus, beta hydrogens are present.
- Conclusion: Beta-elimination **is possible** in this compound.

5. **Option 3: CH3-CH2-CHBr-CH3 (Bromobutane)**:
- Structure: This compound has a carbon chain where the central carbon (alpha carbon) is attached to a bromine atom and two ethyl groups.
- The adjacent carbons (beta carbons) have hydrogen atoms. Thus, beta hydrogens are present.
- Conclusion: Beta-elimination **is possible** in this compound.

6. **Option 4: CH3-CHBr-CH2-CH3 (Bromobutane)**:
- Structure: Similar to the previous option, this compound has a carbon chain where the central carbon (alpha carbon) is attached to a bromine atom and two other carbons.
- The adjacent carbons (beta carbons) have hydrogen atoms. Thus, beta hydrogens are present.
- Conclusion: Beta-elimination **is possible** in this compound.

7. **Final Conclusion**:
- Among the options analyzed, only **Option 1 (CHCl3)** does not have beta hydrogens, making beta-elimination impossible in this compound.

### Answer:
Beta-elimination is not possible in **CHCl3**.