Base strength of the following
(i) `H_(3)C CH_(2)^(-)` , (ii) `H_(2)C=CH^(-)`
(iii) `HC-=C^(-)`

Options

A. `(iii) gt (ii) gt (i)`
B. `(i) gt (iii) gt (ii)`
C. `(i) gt (ii) gt (iii)`
D. `(ii) gt (i) gt (iii)`

Explanation

To determine the base strength of the given compounds, we need to analyze their conjugate acids and their corresponding acidity. The base strength is inversely proportional to the acidity of the conjugate acid.

### Step-by-Step Solution:

1. **Identify the Compounds and Their Conjugate Acids**:
- (i) `H3C-CH2^-` (conjugate acid: `H3C-CH3`)
- (ii) `H2C=CH^-` (conjugate acid: `H2C=CH2`)
- (iii) `HC≡C^-` (conjugate acid: `HC≡CH`)

2. **Determine the Hybridization and S Character**:
- For `H3C-CH2^-`: The carbon is sp³ hybridized (25% s character).
- For `H2C=CH^-`: The carbon is sp² hybridized (33.3% s character).
- For `HC≡C^-`: The carbon is sp hybridized (50% s character).

3. **Analyze Acidity Based on S Character**:
- The acidity increases with increasing s character. Therefore, the order of acidity for the conjugate acids is:
- `HC≡CH` (most acidic)
- `H2C=CH2`
- `H3C-CH3` (least acidic)

4. **Establish the Order of Basic Strength**:
- Since base strength is inversely proportional to acidity, the order of basic strength for the conjugate bases will be the reverse of the order of acidity:
- `HC≡C^-` (most basic)
- `H2C=CH^-`
- `H3C-CH2^-` (least basic)

5. **Final Order of Basic Strength**:
- The final order of basic strength is:
- (iii) `HC≡C^-` > (ii) `H2C=CH^-` > (i) `H3C-CH2^-`

### Summary of the Order:
- Most Basic: `HC≡C^-` (alkyne)
- Moderately Basic: `H2C=CH^-` (alkene)
- Least Basic: `H3C-CH2^-` (alkane)