Give the correct order of decreasing acidity :
`C_(2)H_(5)underset((I))SH`
`C_(2)underset((2))(H_(5)OH`
`C_(2)underset((3))(H_(5)NH_(2)`
`CH_(3)underset((4))(CH_(2)CH_(3)`

Options

A. `2gt1gt3gt4`
B. `3gt2gt1gt4`
C. `1gt2gt3gt4`
D. `3gt4gt2gt1`

Explanation

To determine the correct order of decreasing acidity for the compounds given, we will analyze each compound based on the stability of their conjugate bases.

### Step-by-Step Solution:

1. **Identify the Compounds and Their Conjugate Bases**:
- The first compound is **C₂H₅SH** (ethanethiol), which has a conjugate base of **C₂H₅S⁻**.
- The second compound is **C₂H₅OH** (ethanol), which has a conjugate base of **C₂H₅O⁻**.
- The third compound is **C₂H₅NH₂** (ethylamine), which has a conjugate base of **C₂H₅NH⁻**.
- The fourth compound is **CH₃CH₂CH₃** (propane), which has a conjugate base of **CH₃CH₂C⁻**.

2. **Analyze the Acidity**:
- Acidity is determined by the stability of the conjugate base. The more stable the conjugate base, the stronger the acid.
- The bond strength and length also play a role. A weaker bond (longer bond) means that the hydrogen can be removed more easily, contributing to higher acidity.

3. **Compare the Conjugate Bases**:
- **C₂H₅S⁻ (from C₂H₅SH)**: The S-H bond is weaker than the O-H bond, making it easier to lose H⁺. Thus, C₂H₅SH is more acidic than C₂H₅OH.
- **C₂H₅O⁻ (from C₂H₅OH)**: Oxygen is more electronegative than sulfur, which means that the negative charge on O is more stable than on S. Therefore, ethanol is less acidic than ethanethiol but more acidic than ethylamine.
- **C₂H₅NH⁻ (from C₂H₅NH₂)**: Nitrogen is less electronegative than oxygen, making the negative charge on nitrogen less stable than that on oxygen. Thus, ethylamine is less acidic than ethanol.
- **CH₃CH₂C⁻ (from CH₃CH₂CH₃)**: Carbon is the least electronegative of the atoms involved, making the negative charge on carbon the least stable. Therefore, propane is the least acidic.

4. **Establish the Order of Acidity**:
- Based on the stability of the conjugate bases, we can establish the order of acidity:
1. **C₂H₅SH** (ethanethiol) - most acidic
2. **C₂H₅OH** (ethanol)
3. **C₂H₅NH₂** (ethylamine)
4. **CH₃CH₂CH₃** (propane) - least acidic

### Final Order of Decreasing Acidity:
**C₂H₅SH > C₂H₅OH > C₂H₅NH₂ > CH₃CH₂CH₃**