ElcB` reaction is favoured by stabilisation of carbanion and poor leaving group.
The reaction is kinetically of the second order and unimolecular.

Options

A. If both `(A)` and `(R )` are true, but `( R)` is the correct explanation of `(A)`
B. If both `(A)` and `( R)` are true, but `(R )` is not the correct explanation of `(A)`.
C. If `(A)` is true but `( R)` is false.
D. If `(A)` is false but `( R)` is true.

Answer

### Step-by-Step Solution:

1. **Understanding the E1CB Reaction**:
- The E1CB (unimolecular elimination via a conjugate base) reaction involves the formation of a carbanion intermediate. This reaction typically occurs when the leaving group is poor, meaning it does not easily dissociate from the molecule.

2. **Formation of Carbanion**:
- In the E1CB mechanism, a base abstracts a proton (H+) from the substrate, leading to the formation of a carbanion. This step is crucial as it is the rate-determining step of the reaction.

3. **Stabilization of Carbanion**:
- The stability of the carbanion is essential for the reaction to proceed. More stable carbanions will lead to a faster reaction rate. Factors that stabilize carbanions include resonance, inductive effects, and hybridization.

4. **Kinetics of the Reaction**:
- The E1CB reaction is second-order because the rate depends on the concentration of both the substrate (alkyl halide) and the base. However, it is also considered unimolecular because the rate-determining step involves only the substrate and the base in the formation of the carbanion.

5. **Rate Law**:
- The rate law for the E1CB reaction can be expressed as:
\[ \text{Rate} = k[\text{alkyl halide}][\text{base}] \]
- This indicates that the reaction rate is influenced by the concentrations of both the alkyl halide and the base.

6. **Conclusion**:
- The assertion that the E1CB reaction is favored by the stabilization of the carbanion and poor leaving group is correct. The reason provided, that the reaction is second-order and unimolecular, is also correct but does not adequately explain the assertion. The correct explanation should focus on the relationship between carbanion stability and reaction rate.