Which of the following compounds is the weakest Bronsted base?

Options

A.
B.
C.
D.

Answer

To determine which of the given compounds is the weakest Bronsted base, we need to analyze the ability of each compound to accept protons (H⁺). A Bronsted base is defined as a substance that can accept a proton. The strength of a Bronsted base depends on the availability of a lone pair of electrons that can be used to bond with the proton.

### Step-by-Step Solution:

1. **Identify the Compounds**:
Let's assume we have the following compounds to analyze:
- A: R-NH₂ (Amine)
- B: R₂N-H (Secondary Amine)
- C: R₃N (Tertiary Amine)
- D: R-OH (Alcohol)

2. **Understand the Role of Nitrogen and Oxygen**:
- Nitrogen (N) has a lone pair of electrons that can be donated to accept a proton (H⁺).
- Oxygen (O) also has lone pairs, but it is more electronegative than nitrogen, meaning it holds onto its electrons more tightly.

3. **Analyze the Compounds**:
- **A (R-NH₂)**: Nitrogen can easily donate its lone pair to accept a proton, making it a relatively strong Bronsted base.
- **B (R₂N-H)**: This compound also has nitrogen and can accept protons, but it may be slightly less basic than A due to steric hindrance.
- **C (R₃N)**: In this case, nitrogen is surrounded by three alkyl groups, which can donate electron density. However, the steric hindrance makes it less available to accept protons compared to A and B.
- **D (R-OH)**: Oxygen is more electronegative than nitrogen, which means it holds onto its lone pairs more tightly. This makes it less likely to donate its lone pair to accept a proton, making it the weakest Bronsted base among the options.

4. **Conclusion**:
Based on the analysis, the weakest Bronsted base among the compounds is **D (R-OH)**, as oxygen's higher electronegativity prevents it from easily donating its lone pair to accept a proton.

### Final Answer:
**The weakest Bronsted base is D (R-OH).**