Which of the following would you predict to be the stronger acid ? `CH_(3) - CH = CH - CH_(2) - OH " or " CH_(3) - CH = CH - OH `

Answer

To determine which of the two compounds is the stronger acid, we need to analyze the stability of their conjugate bases after the loss of a proton (H⁺).

### Step-by-Step Solution:

1. **Identify the Compounds**:
- Compound 1: `CH₃ - CH = CH - CH₂ - OH`
- Compound 2: `CH₃ - CH = CH - OH`

2. **Determine the Conjugate Bases**:
- For Compound 1, when the hydroxyl group (OH) loses a proton (H⁺), the conjugate base formed is:
- `CH₃ - CH = CH - CH₂ - O⁻`
- For Compound 2, when the hydroxyl group (OH) loses a proton (H⁺), the conjugate base formed is:
- `CH₃ - CH = CH - O⁻`

3. **Analyze the Stability of the Conjugate Bases**:
- **Compound 1 Conjugate Base**:
- `CH₃ - CH = CH - CH₂ - O⁻` does not have resonance stabilization because the negative charge on the oxygen cannot be delocalized effectively.
- **Compound 2 Conjugate Base**:
- `CH₃ - CH = CH - O⁻` can have resonance stabilization. The negative charge on the oxygen can be delocalized into the double bond, allowing for resonance structures that stabilize the conjugate base.

4. **Compare the Stability**:
- The conjugate base of Compound 2 is more stable due to resonance, while the conjugate base of Compound 1 lacks such stabilization.

5. **Conclusion**:
- Since the conjugate base of Compound 2 is more stable, we can conclude that Compound 2 (`CH₃ - CH = CH - OH`) is the stronger acid compared to Compound 1 (`CH₃ - CH = CH - CH₂ - OH`).

### Final Answer:
**The stronger acid is `CH₃ - CH = CH - OH`.**