Bromocyclodecane on heating with ethanolic KOH, produces two alkenes. Write the two products also mentions the major one.

Answer

To solve the problem of what products are formed when bromocyclodecane is heated with ethanolic KOH, we can follow these steps:

### Step 1: Understand the Reactant
Bromocyclodecane is a cyclic alkane with a bromine atom attached. The structure can be represented as follows:

```
Br
|
C1 - C2
/ \
C10 C3
| |
C9 C4
| |
C8 C5
\ /
C7 - C6
```

### Step 2: Identify the Reaction Type
When bromocyclodecane is treated with ethanolic KOH, an elimination reaction occurs. This is typically an E2 elimination where the bromine atom is removed along with a hydrogen atom from an adjacent carbon.

### Step 3: Determine Possible Elimination Sites
In bromocyclodecane, elimination can occur from two different positions:
1. Removing a hydrogen from the carbon adjacent to the carbon with the bromine (C1 or C2).
2. This can lead to the formation of two different alkenes.

### Step 4: Draw the Possible Products
1. **Cis Product**: When elimination occurs between C1 and C2, the product formed is a cis-alkene.
2. **Trans Product**: When elimination occurs between C1 and C2 but from the opposite side, the product formed is a trans-alkene.

The structures can be represented as follows:
- **Cis Product**:
```
H
\
C1 = C2
/ \
C10 C3
| |
C9 C4
| |
C8 C5
\ /
C7 - C6
```
- **Trans Product**:
```
H
\
C1 = C2
/ \
C10 C3
| |
C9 C4
| |
C8 C5
\ /
C7 - C6
```

### Step 5: Identify the Major Product
In elimination reactions, the stability of the alkene plays a crucial role in determining the major product. Generally, the more substituted alkene is more stable and thus is favored in elimination reactions.

In this case, the **cis product** is more stable due to steric factors and is therefore the major product. The **trans product** is less stable and is the minor product.

### Conclusion
The two products formed from the reaction of bromocyclodecane with ethanolic KOH are:
1. **Cis-alkene** (major product)
2. **Trans-alkene** (minor product)