Arrange the following compounds in the decreasing order of acidic character.
`I.` Butane ,`II.` but`-1-`ene
`III.` But`-1-` yne `IV.` Butan `-1-`ol

Options

A. `(I)gt(II)gt(III)gt(IV)`
B. `(IV)gt(II)gt(III)gt(I)`
C. `(IV)gt(III)gt(II)gt(I)`
D. `(I)gt(III)gt(II)gt(IV)`

Explanation

To arrange the compounds Butane, But-1-ene, But-1-yne, and Butan-1-ol in decreasing order of acidic character, we need to analyze the acidic strength of each compound based on their structures and hybridization.

### Step 1: Identify the Structures
1. **Butane (I)**: CH₃-CH₂-CH₂-CH₃ (sp³ hybridized)
2. **But-1-ene (II)**: CH₃-CH₂-CH=CH₂ (sp² hybridized)
3. **But-1-yne (III)**: CH₃-CH₂-C≡CH (sp hybridized)
4. **Butan-1-ol (IV)**: CH₃-CH₂-CH₂-CH₂OH (contains an -OH group)

### Step 2: Determine Hybridization and % s-Character
- **Butane (I)**: sp³ hybridization → 25% s-character
- **But-1-ene (II)**: sp² hybridization → 33.33% s-character
- **But-1-yne (III)**: sp hybridization → 50% s-character
- **Butan-1-ol (IV)**: The presence of the -OH group makes it acidic due to the electronegativity of oxygen.

### Step 3: Analyze Acidic Strength
- The acidic strength of a compound is influenced by the hybridization of the carbon atom bonded to the hydrogen atom that can be released as a proton (H⁺). The higher the s-character, the more acidic the compound tends to be because of increased electronegativity.
- **But-1-yne (III)** has the highest s-character (50%), making it the most acidic.
- **Butan-1-ol (IV)** is next due to the presence of the -OH group, which is highly electronegative and stabilizes the negative charge after deprotonation.
- **But-1-ene (II)** follows with 33.33% s-character.
- **Butane (I)** has the least acidic character with 25% s-character.

### Step 4: Final Order
Based on the analysis, the order of acidic character from highest to lowest is:
1. **Butan-1-ol (IV)**
2. **But-1-yne (III)**
3. **But-1-ene (II)**
4. **Butane (I)**

### Final Answer
The decreasing order of acidic character is:
**IV > III > II > I**