When trans-2-butene reacts with `Br_2//C Cl_4`, X number of products are formed. Whereas when trans-2-butene reacts with HBr Y number of products are formed . Report your answer as Y X .

Answer

To solve the problem, we need to analyze the reactions of trans-2-butene with both Br2 in CCl4 and HBr.

### Step 1: Reaction of trans-2-butene with Br2 in CCl4
1. **Identify the structure of trans-2-butene**: The molecular formula is C4H8, and its structure is CH3-CH=CH-CH3 with the two CH3 groups on opposite sides of the double bond.
2. **Reaction with Br2**: When trans-2-butene reacts with bromine (Br2) in carbon tetrachloride (CCl4), it undergoes an electrophilic addition reaction.
3. **Formation of products**: The addition of Br2 across the double bond leads to the formation of two meso compounds:
- 2,3-dibromobutane (one with Br on the same side and one with Br on the opposite side).
4. **Count the products**: Since both products are meso compounds, they are considered as one unique product in terms of stereochemistry.
5. **Conclusion for x**: Therefore, the total number of distinct products formed is **2**.

### Step 2: Reaction of trans-2-butene with HBr
1. **Reaction with HBr**: When trans-2-butene reacts with hydrogen bromide (HBr), it also undergoes an electrophilic addition reaction.
2. **Formation of products**: The addition of HBr leads to the formation of 2-bromobutane.
3. **Count the products**: In this case, only one product is formed regardless of the stereochemistry.
4. **Conclusion for y**: Therefore, the total number of distinct products formed is **1**.

### Final Answer
Now, we report the answer as Y X:
- y = 1 (from the reaction with HBr)
- x = 2 (from the reaction with Br2 in CCl4)

Thus, the final answer is **1 2**.