Decreasing order of stability of following alkenes is
(i) `CH_(3)-cH=CH_(2)`
(ii) `CH_(3)-CH=CH-CH_(3)`
`CH_(3)-underset(CH_(3))underset("| ")"C "=CH-CH_(3)`
(iv) `CH_(3)-overset(CH_(3))overset("| ")"C "=overset(CH_(3))overset("| ")"C "-CH_(3)`

Options

A. `(i) >(ii) > (iii) > (iv)
B. (iv) > (iii) >(ii) >(i)
C. (iii) > (ii) > (i) > (iv)
D. (ii) > (iii) >(iv) > (i)

Answer

To determine the decreasing order of stability of the given alkenes, we need to analyze each alkene based on the number of alpha hydrogens and the degree of substitution. The stability of alkenes increases with the number of alkyl substituents due to hyperconjugation.

### Step-by-Step Solution:

1. **Identify the Alkenes**:
- (i) `CH₃-CH=CH₂` (Mono-substituted)
- (ii) `CH₃-CH=CH-CH₃` (Di-substituted)
- (iii) `CH₃-C(CH₃)=CH-CH₃` (Tri-substituted)
- (iv) `CH₃-C(CH₃)=C(CH₃)-CH₃` (Tetra-substituted)

2. **Count Alpha Hydrogens**:
- **Alkene (i)**: `CH₃-CH=CH₂` has 3 alpha hydrogens (from CH₃).
- **Alkene (ii)**: `CH₃-CH=CH-CH₃` has 6 alpha hydrogens (3 from each CH₃).
- **Alkene (iii)**: `CH₃-C(CH₃)=CH-CH₃` has 9 alpha hydrogens (3 from each CH₃ and 3 from the other CH₃).
- **Alkene (iv)**: `CH₃-C(CH₃)=C(CH₃)-CH₃` has 12 alpha hydrogens (3 from each CH₃).

3. **Determine Stability Based on Substitution**:
- The stability of alkenes increases with the degree of substitution:
- Tetra-substituted (iv) > Tri-substituted (iii) > Di-substituted (ii) > Mono-substituted (i).

4. **Rank the Alkenes**:
- Based on the analysis, the order of stability is:
- (iv) > (iii) > (ii) > (i)

5. **Final Answer**:
- The decreasing order of stability of the alkenes is:
- `CH₃-C(CH₃)=C(CH₃)-CH₃` > `CH₃-C(CH₃)=CH-CH₃` > `CH₃-CH=CH-CH₃` > `CH₃-CH=CH₂`