Most acidic species among the following is

Options

A. `CH_(3)-overset(O)overset(||)(C)-CH_(3)`
B. `CH_(3)-O-H`
C. `CH_(3)-C-=C-H`
D.

Answer

To determine the most acidic species among the given options, we will analyze the conjugate bases formed by removing a proton (H⁺) from each species. The stability of these conjugate bases will help us identify the most acidic species.

### Step-by-Step Solution:

1. **Identify the Species**: List the given species for which we need to find the most acidic one. For this example, let's assume the species are:
- A: CH₃C(=O)H (Acetaldehyde)
- B: CH₃OH (Methanol)
- C: CH₃C≡COH (Propyne)
- D: C₆H₅COOH (Benzoic acid)

2. **Form Conjugate Bases**: Remove H⁺ from each species to form their respective conjugate bases:
- A: CH₃C(=O)⁻ (Conjugate base of Acetaldehyde)
- B: CH₃O⁻ (Conjugate base of Methanol)
- C: CH₃C≡C⁻ (Conjugate base of Propyne)
- D: C₆H₅COO⁻ (Conjugate base of Benzoic acid)

3. **Analyze Stability of Conjugate Bases**:
- **Conjugate Base of A (Acetaldehyde)**: The negative charge is on a carbon atom, which is stabilized by resonance with the carbonyl group.
- **Conjugate Base of B (Methanol)**: The negative charge is on oxygen, which is highly electronegative and can stabilize the charge effectively.
- **Conjugate Base of C (Propyne)**: The negative charge is on a carbon atom, which is sp-hybridized. This gives it some stability due to the high s-character.
- **Conjugate Base of D (Benzoic acid)**: The negative charge is on the carboxylate ion (C₆H₅COO⁻), which is stabilized by resonance across the aromatic ring.

4. **Compare Stability**:
- The conjugate base of methanol (B) has the negative charge on oxygen, making it very stable.
- The conjugate base of benzoic acid (D) is also stable due to resonance.
- The conjugate bases of acetaldehyde (A) and propyne (C) are less stable since their negative charges are on carbon atoms.

5. **Conclusion**:
- The most stable conjugate base corresponds to the strongest acid.
- Since the conjugate base of benzoic acid (D) is highly stabilized by resonance, it is the most acidic species among the given options.

### Final Answer:
The most acidic species among the given options is **D: C₆H₅COOH (Benzoic acid)**.