Which of the following is weaker base?

Options

A. `N(SiH_(3))^(3)`
B. `N(CH_(3))_(3)`
C. `NH(CH_(3))_(2)`
D. All are equally basic

Explanation

To determine which of the given options is a weaker base, we need to analyze the basicity of the compounds based on the ability of their donor atoms to donate lone pairs of electrons. Here’s a step-by-step solution:

### Step 1: Understand Basicity
Basicity is defined as the ability of a species to donate a lone pair of electrons. The stronger the base, the more readily it can donate its lone pair.

**Hint:** Remember that the presence of electron-donating groups can enhance basicity.

### Step 2: Analyze the Compounds
We have three nitrogen-containing compounds to analyze:
1. Compound 1: Nitrogen connected to silicon hydride.
2. Compound 2: Nitrogen connected to two methyl groups.
3. Compound 3: Nitrogen connected to one hydrogen and two methyl groups.

**Hint:** Look for the central atom and its connectivity to understand the electron density.

### Step 3: Evaluate Compound 1
In Compound 1, the nitrogen has a lone pair, but it is connected to silicon, which has empty d-orbitals. This allows for back-bonding, where the lone pair from nitrogen can be attracted to the empty orbitals of silicon. This reduces the availability of the lone pair for donation, making it less basic.

**Hint:** Consider how back-bonding affects the availability of lone pairs.

### Step 4: Evaluate Compound 2
In Compound 2, nitrogen is connected to two methyl groups. Methyl groups are electron-donating (through +I effect), which increases the electron density on nitrogen, making it more basic compared to Compound 1.

**Hint:** Remember that more electron-donating groups generally increase basicity.

### Step 5: Evaluate Compound 3
In Compound 3, nitrogen is connected to one hydrogen and two methyl groups. While it has similar electron-donating groups as Compound 2, it is a tertiary amine. Tertiary amines are generally expected to be more basic due to the presence of three methyl groups. However, steric hindrance can affect the ability of the nitrogen to interact with electrophiles.

**Hint:** Consider how steric hindrance can impact basicity, especially in tertiary amines.

### Step 6: Compare Basicities
- **Compound 1**: Weakest base due to back-bonding with silicon.
- **Compound 2**: Stronger base than Compound 1 due to two methyl groups.
- **Compound 3**: Expected to be strong but is hindered by steric factors, making it less basic than Compound 2.

### Conclusion
Based on the analysis, Compound 1 (nitrogen connected to silicon hydride) is the weakest base among the options provided.

**Final Answer:** Compound 1 is the weaker base.