Consider the following alkenes :
1. `H_(2)C=C(CH_(2)CH_(3))CH(CH_(3))_(2)`
2. `(CH_(3))_(2)C=C(CH_(3))CH_(2)CH_(3)`
3. `CH_(3)CH=C(CH_(3))CH(CH_(3))_(2)`
The correct sequence of increasing order of stability of these alkenes is :

Options

A. 1,2,3
B. 3,2,1
C. 2,1,3
D. 1,3,2.

Explanation

To determine the stability of the given alkenes, we will analyze the number of alpha-hydrogens present in each compound. The more alpha-hydrogens an alkene has, the more stable it is due to the hyperconjugation effect.

### Step 1: Identify the Structures of the Alkenes
1. **Alkene 1**: `H2C=C(CH2CH3)CH(CH3)2`
2. **Alkene 2**: `(CH3)2C=C(CH3)CH2CH3`
3. **Alkene 3**: `CH3CH=C(CH3)CH(CH3)2`

### Step 2: Count the Alpha-Hydrogens
- **Alpha-hydrogens** are the hydrogens attached to the carbons adjacent to the double bond.

#### For Alkene 1:
- The structure is: `H2C=C(CH2CH3)CH(CH3)2`
- The carbons adjacent to the double bond are:
- CH2 (from CH2CH3) has 2 alpha-hydrogens.
- CH (from CH(CH3)2) has 1 alpha-hydrogen.
- Total alpha-hydrogens = 2 + 1 = **3 alpha-hydrogens**.

#### For Alkene 2:
- The structure is: `(CH3)2C=C(CH3)CH2CH3`
- The carbons adjacent to the double bond are:
- C (from (CH3)2) has 6 alpha-hydrogens (3 from each CH3).
- CH2 (from CH2CH3) has 2 alpha-hydrogens.
- Total alpha-hydrogens = 6 + 2 = **8 alpha-hydrogens**.

#### For Alkene 3:
- The structure is: `CH3CH=C(CH3)CH(CH3)2`
- The carbons adjacent to the double bond are:
- CH3 (from CH3) has 3 alpha-hydrogens.
- CH (from C(CH3)CH(CH3)2) has 1 alpha-hydrogen.
- CH (from CH(CH3)2) has 1 alpha-hydrogen.
- Total alpha-hydrogens = 3 + 1 + 1 = **5 alpha-hydrogens**.

### Step 3: Determine the Stability Order
Now, we can summarize the findings:
- Alkene 1 has **3 alpha-hydrogens** (least stable).
- Alkene 3 has **5 alpha-hydrogens** (moderately stable).
- Alkene 2 has **8 alpha-hydrogens** (most stable).

### Conclusion
The correct sequence of increasing order of stability of these alkenes is:
**Alkene 1 < Alkene 3 < Alkene 2**.

### Final Answer
1. **Alkene 1** (least stable)
2. **Alkene 3** (moderately stable)
3. **Alkene 2** (most stable)