Which of the following compounds will not dissolve in aqueous NaOH?

Options

A.
B.
C.
D.

Answer

To determine which compound will not dissolve in aqueous NaOH, we need to analyze the stability of the conjugate bases formed when each compound reacts with NaOH. Here’s a step-by-step solution:

### Step 1: Understand the Role of Aqueous NaOH
Aqueous NaOH is a strong base that can deprotonate (remove a hydrogen ion, H⁺) acidic compounds. When a compound is deprotonated, it forms a conjugate base. The stability of this conjugate base will determine whether the compound dissolves in NaOH.

### Step 2: Analyze Each Compound
1. **First Compound**: When NaOH is added, the most acidic hydrogen is removed, forming a conjugate base. The negative charge on oxygen can participate in resonance, stabilizing the conjugate base. Therefore, this compound will dissolve in NaOH.

2. **Second Compound**: Similar to the first, when NaOH abstracts a hydrogen, it forms a conjugate base with a negative charge on oxygen. This negative charge is also stabilized by resonance with a double bond. Thus, this compound will also dissolve in NaOH.

3. **Third Compound (FOH)**: Upon deprotonation, it forms a conjugate base with a negative charge on oxygen (O⁻). However, this negative charge does not have resonance stabilization, making it less stable compared to the previous cases. Therefore, this compound is less likely to dissolve in NaOH.

4. **Fourth Compound**: When deprotonated, the conjugate base has a negative charge on sulfur. Sulfur, being larger than oxygen, can stabilize the negative charge better due to its size. Thus, this compound will dissolve in NaOH.

### Step 3: Conclusion
Based on the analysis, the third compound (FOH) does not have a stable conjugate base due to the lack of resonance stabilization and is therefore the compound that will not dissolve in aqueous NaOH.

### Final Answer
The compound that will not dissolve in aqueous NaOH is the **third compound (FOH)**.

---