Which of the following is strongest Lewis base?

Options

A. `CH_(3)^(-)`
B. `F^(-)`
C. `NH_(2)^(-)`
D. `OH^(-)`

Answer

To determine which of the following is the strongest Lewis base among the given options (CH3-, F-, NH2-, and OH-), we will follow these steps:

### Step 1: Understand the Concept of Lewis Bases
A Lewis base is defined as a species that can donate an electron pair. Therefore, the strength of a Lewis base is related to its ability to donate electrons.

**Hint:** Remember that the more unstable a species is, the more likely it is to donate its electrons, making it a stronger Lewis base.

### Step 2: Analyze the Given Species
We have four species to consider:
1. CH3- (methyl anion)
2. F- (fluoride ion)
3. NH2- (amide ion)
4. OH- (hydroxide ion)

**Hint:** Look at the electronegativity of the atoms involved, as it will help determine the stability of the negative charge.

### Step 3: Evaluate Stability Based on Electronegativity
The stability of the negative charge on these species is influenced by the electronegativity of the atoms:
- Fluorine (F) is the most electronegative, making F- the most stable.
- Oxygen (O) is next, making OH- more stable than NH2-.
- Nitrogen (N) is less electronegative than oxygen, so NH2- is less stable than OH-.
- Carbon (C) is the least electronegative, making CH3- the least stable.

**Hint:** The more electronegative the atom, the more stable the negative charge will be on it.

### Step 4: Determine the Order of Stability
From the analysis, we can establish the order of stability based on electronegativity:
- F- (most stable)
- OH-
- NH2-
- CH3- (least stable)

**Hint:** The least stable species will be the strongest Lewis base.

### Step 5: Determine the Order of Basicity
Since basicity is inversely related to stability, the order of basicity (from strongest to weakest) will be:
1. CH3- (strongest base)
2. NH2-
3. OH-
4. F- (weakest base)

**Hint:** The strongest Lewis base will be the one that is least stable.

### Step 6: Conclusion
Based on the analysis, the strongest Lewis base among the given options is **CH3-**.

**Final Answer:** CH3- is the strongest Lewis base.