In `HS^(-)`, `I^(-)`, `R-NH_(2)`, `NH_(3)` order of proton accepting tendency will be

Options

A. `I^- gt NH_3 gt R -NH_2 gt HS^-`
B. `NH_3 gt R -NH_2 gt HS^- gt I^-`
C. `R-NH_2 gt NH_3 gt HS^- gt I^-`
D. `HS^- gt R-NH_2 gt NH_3 gt I^-`

Answer

To determine the order of proton-accepting tendency (basicity) for the species HS^(-), I^(-), R-NH2, and NH3, we can analyze their basic properties step by step.

### Step 1: Understand Basicity
Basicity refers to the ability of a species to accept protons (H^+ ions). The stronger the base, the more readily it will accept a proton.

### Step 2: Compare R-NH2 and NH3
- **R-NH2 (Alkylamine)**: This is a strong base due to the +I (inductive) effect of the alkyl group (R). The alkyl group donates electron density to the nitrogen atom, making it more capable of accepting a proton.
- **NH3 (Ammonia)**: Ammonia is a weaker base compared to R-NH2 because it lacks the electron-donating alkyl group.

**Conclusion for Step 2**: R-NH2 > NH3 in terms of basicity.

### Step 3: Compare HS^(-) and I^(-)
- **HS^(-) (Hydrosulfide ion)**: This is the conjugate base of H2S, which is a weak acid. Therefore, HS^(-) is a relatively stronger base.
- **I^(-) (Iodide ion)**: This is the conjugate base of HI, which is a strong acid. The stronger the acid, the weaker its conjugate base. Therefore, I^(-) is a weak base.

**Conclusion for Step 3**: HS^(-) > I^(-) in terms of basicity.

### Step 4: Combine the Results
Now we can combine our findings:
1. R-NH2 is the strongest base.
2. NH3 is the next strongest base.
3. HS^(-) follows NH3.
4. I^(-) is the weakest base.

### Final Order of Proton-Accepting Tendency
The order of proton-accepting tendency (basicity) is:
**R-NH2 > NH3 > HS^(-) > I^(-)**