Which of the following orders of acid strength is correct?

Options

A. `RCOOH gt HOH gt HC -=CH gt ROH`
B. `RCOOH gt RC -= CH gt HOH gt ROH`
C. `RCOOH gt ROH gt HOH gt HC -=CH`
D. `RCOOH gt HOH gt ROH gt HC -=CH`

Explanation

To determine the correct order of acid strength among the given compounds, we need to analyze the stability of their conjugate bases. The more stable the conjugate base, the stronger the corresponding acid.

### Step-by-Step Solution:

1. **Identify the Compounds**: The compounds we need to analyze are:
- RCOH (Carboxylic acid)
- HOH (Water)
- ROH (Alcohol)
- HC≡CH (Alkyne)

2. **Determine the Conjugate Bases**:
- For RCOH, the conjugate base is RCOO⁻ (carboxylate ion).
- For HOH, the conjugate base is OH⁻ (hydroxide ion).
- For ROH, the conjugate base is RO⁻ (alkoxide ion).
- For HC≡CH, the conjugate base is C≡C⁻ (acetylide ion).

3. **Analyze the Stability of Conjugate Bases**:
- **RCOO⁻**: This ion is stabilized by resonance. The negative charge can be delocalized between the two oxygen atoms, making it quite stable.
- **OH⁻**: This ion is relatively stable as it has a negative charge localized on one oxygen atom.
- **RO⁻**: The alkoxide ion is less stable than hydroxide because the R group can destabilize the negative charge due to its +I (inductive) effect.
- **C≡C⁻**: The negative charge on carbon is not stable because carbon is less electronegative than oxygen. Therefore, this ion is the least stable.

4. **Rank the Acids Based on Conjugate Base Stability**:
- Since RCOO⁻ is the most stable, RCOH is the strongest acid.
- Next is HOH, as OH⁻ is more stable than RO⁻.
- ROH is weaker than HOH due to the destabilizing effect of the R group.
- Finally, HC≡CH is the weakest acid because C≡C⁻ is the least stable conjugate base.

5. **Final Order of Acid Strength**:
- RCOH > HOH > ROH > HC≡CH

### Conclusion:
The correct order of acid strength is:
**RCOH > HOH > ROH > HC≡CH**