The weakest acid (does not show acidic character) is:

Options

A. `HC-=CH`
B. `CH_(2)=CH_(2)`
C. `Me_(3)CH`
D. `Ph_(3)CH`

Answer

To determine the weakest acid among the given options, we need to analyze the stability of the anions produced when each acid ionizes. The stability of the anion is crucial because a more stable anion corresponds to a stronger acid.

### Step-by-Step Solution:

1. **Understanding Acidity**:
- Acidity is related to the stability of the anion formed after the acid donates a proton (H+). The more stable the anion, the stronger the acid.

2. **Analyzing the First Compound (Ethyne, CH≡CH)**:
- Upon ionization, ethyne produces HC≡C⁻ (an anion).
- The carbon in the anion is sp-hybridized, which has higher electronegativity compared to sp² or sp³ hybridized carbons.
- Therefore, the anion is relatively stable, indicating that ethyne is an acidic compound.

3. **Analyzing the Second Compound (Ethene, CH₂=CH₂)**:
- Ethene ionizes to produce CH₂=C⁻ (an anion).
- The carbon in this anion is sp²-hybridized, which is less electronegative than sp-hybridized carbon.
- Thus, the anion is less stable than that of ethyne, but still shows some acidic character.

4. **Analyzing the Third Compound (tert-Butyl anion, (CH₃)₃C⁻)**:
- This compound ionizes to produce a carbanion with three methyl groups attached.
- The presence of three electron-donating methyl groups increases the electron density on the anion, making it less stable.
- Therefore, this compound is expected to be the least acidic.

5. **Analyzing the Fourth Compound (Triphenylmethane, (C₆H₅)₃C⁻)**:
- This compound ionizes to produce a carbanion that is stabilized by resonance due to the three phenyl groups.
- The resonance stabilization makes this anion very stable, indicating that this compound is a strong acid.

6. **Conclusion**:
- Comparing the stability of the anions produced from all four compounds, the weakest acid is the one that produces the least stable anion.
- The weakest acid, which does not show significant acidic character, is (CH₃)₃C⁻ (the tert-butyl anion).

### Final Answer:
The weakest acid (does not show acidic character) is (CH₃)₃C⁻ (tert-butyl anion).