Which of the following reactions would give racemised and retention products ?

Options

A.
B.
C.
D.

Explanation

To determine which reactions would give racemized and retention products, we need to analyze the nature of the reactions involved, particularly focusing on whether they are SN1 reactions. SN1 reactions are characterized by the formation of a planar carbocation intermediate, which allows for attack from either side, leading to a mixture of products.

### Step-by-Step Solution:

1. **Understanding SN1 Mechanism**:
- In SN1 reactions, the leaving group departs first, forming a carbocation. This carbocation is planar and can be attacked by the nucleophile from either side.
- If the carbon atom is chiral, this can lead to both retention (where the configuration remains the same) and racemization (where both configurations are formed).

2. **Analyzing the Options**:
- **Option A**: The carbon atom has four different groups (methyl, ethyl, hydrogen, and bromine). When bromine leaves, it forms a chiral carbocation. The nucleophile (OH-) can attack from either side, leading to both retention and racemized products. Therefore, this option is correct.

- **Option B**: This carbon atom is also chiral with four different groups. Similar to option A, the leaving of bromine forms a planar carbocation, allowing for both types of products (retention and racemization). This option is also correct.

- **Option C**: The carbon atom has two ethyl groups, making it achiral. Since there is no chiral center, it cannot produce racemized or retention products. This option is incorrect.

- **Option D**: This carbon atom is chiral. Upon the departure of the leaving group, a planar carbocation is formed, allowing for attack from both sides. This results in both retention and racemized products. Thus, this option is correct.

3. **Conclusion**:
- The reactions that would give racemized and retention products are found in options A, B, and D.

### Final Answer:
The correct options that give racemized and retention products are A, B, and D.