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 options CH3⁻, F⁻, NH2⁻, and OH⁻, we can follow these steps:

### Step 1: Understand Lewis Bases
Lewis bases are defined as substances that can donate a pair of electrons. The strength of a Lewis base is influenced by its ability to donate these electrons, which is affected by the electronegativity of the atom involved.

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

### Step 3: Consider Electronegativity
Electronegativity is the tendency of an atom to attract electrons. The lower the electronegativity of the atom, the more readily it can donate its electrons, making it a stronger Lewis base. The electronegativity values for the relevant atoms are as follows:
- Carbon (C) < Nitrogen (N) < Oxygen (O) < Fluorine (F)

### Step 4: Determine the Order of Electronegativity
From the electronegativity values, we can establish the following order:
- F⁻ (most electronegative)
- OH⁻ (less electronegative than F)
- NH2⁻ (less electronegative than OH)
- CH3⁻ (least electronegative)

### Step 5: Relate Electronegativity to Lewis Base Strength
Since Lewis base strength is inversely proportional to electronegativity, we can deduce the following order of Lewis base strength:
- CH3⁻ > NH2⁻ > OH⁻ > F⁻

### Step 6: Identify the Strongest Lewis Base
From our analysis, CH3⁻ has the lowest electronegativity and therefore is the strongest Lewis base among the given options.

### Conclusion
The strongest Lewis base among the options is **CH3⁻**.

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