Maximum basic in gas phase is ?

Options

A. `NH_(3)`
B. `CH_(3)CH_(2)NH_(2)`
C. `(CH_(3)CH_(2))NH`
D. `(CH_(3)CH_(2))_(3)N`

Answer

To determine which compound is the most basic in the gas phase among the given options, we will analyze the basicity of the amines based on the inductive effect of the alkyl groups attached to the nitrogen atom.

### Step-by-Step Solution:

1. **Understanding Basicity in Amines**:
Basicity in amines is primarily influenced by the availability of the lone pair of electrons on the nitrogen atom. The more electron-donating groups attached to the nitrogen, the more available the lone pair becomes for donation, thus increasing basicity.

2. **Identifying the Compounds**:
The question provides four compounds: ammonia (NH3) and three amines with varying numbers of alkyl groups (ethyl groups in this case). We will denote them as follows:
- A: Ammonia (NH3)
- B: Primary amine (one ethyl group)
- C: Secondary amine (two ethyl groups)
- D: Tertiary amine (three ethyl groups)

3. **Evaluating the Inductive Effect**:
- Alkyl groups exhibit a +I (positive inductive) effect, which means they donate electron density towards the nitrogen atom.
- The more alkyl groups attached to the nitrogen, the greater the electron donation and the stronger the basicity.

4. **Comparing the Basicity**:
- **Ammonia (A)**: No alkyl groups, so it has the least basicity.
- **Primary Amine (B)**: One ethyl group provides some +I effect, increasing basicity compared to ammonia.
- **Secondary Amine (C)**: Two ethyl groups provide more +I effect, thus increasing basicity further.
- **Tertiary Amine (D)**: Three ethyl groups provide the maximum +I effect, making it the most basic.

5. **Conclusion**:
In the gas phase, steric hindrance is not a significant factor, so we only consider the inductive effect. Therefore, the tertiary amine (D) with three ethyl groups is the most basic.

### Final Answer:
The compound that is the most basic in the gas phase is **Option D (Tertiary Amine)**.

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