Among the following alkenes,
(I)1 - butene
(II) cis -2- butene
(III) trans -2- butene
the decreasing order of stability is

Options

A. `II gt I gt III`
B. `III gt II gt I`
C. `III gt I gt II`
D. `I gt II gt III`

Explanation

To determine the decreasing order of stability among the given alkenes (1-butene, cis-2-butene, and trans-2-butene), we need to analyze the structure and stability of each alkene based on steric hindrance and the nature of substituents around the double bond.

### Step-by-Step Solution:

1. **Identify the Structures of the Alkenes:**
- **1-butene (I)**: This is a straight-chain alkene with the structure CH2=CH-CH2-CH3. It has a terminal double bond.
- **cis-2-butene (II)**: This alkene has the structure CH3-CH=CH-CH3, where the two methyl groups (CH3) are on the same side of the double bond.
- **trans-2-butene (III)**: This alkene also has the structure CH3-CH=CH-CH3, but the two methyl groups are on opposite sides of the double bond.

2. **Analyze Stability:**
- **1-butene**: Being a terminal alkene, it has less steric hindrance compared to the others, but it is generally less stable than internal alkenes.
- **cis-2-butene**: This configuration has steric strain due to the proximity of the two methyl groups on the same side of the double bond, making it less stable than trans-2-butene.
- **trans-2-butene**: This alkene is more stable than both 1-butene and cis-2-butene because the bulky methyl groups are positioned on opposite sides of the double bond, reducing steric hindrance.

3. **Rank the Stability:**
- From the analysis, we can conclude the stability order:
- **Most Stable**: trans-2-butene (III)
- **Moderately Stable**: 1-butene (I)
- **Least Stable**: cis-2-butene (II)

4. **Final Order of Stability**:
- The decreasing order of stability is: **trans-2-butene (III) > 1-butene (I) > cis-2-butene (II)**.