Which one of the following is not a primary amine ?

Options

A. tert-Butylamine
B. Dimethylamine
C. sec-Butylamine
D. iso-Butylamine

Answer

To determine which compound is not a primary amine among the given options, we first need to understand the classification of amines based on the number of hydrogen atoms attached to the nitrogen atom.

### Step 1: Understand the classification of amines
- **Primary amines (1°)**: The nitrogen atom is bonded to one carbon atom and has two hydrogen atoms (R-NH2).
- **Secondary amines (2°)**: The nitrogen atom is bonded to two carbon atoms and has one hydrogen atom (R2-NH).
- **Tertiary amines (3°)**: The nitrogen atom is bonded to three carbon atoms and has no hydrogen atoms (R3-N).

### Step 2: Analyze the given options
1. **Tert-butyl amine**: This has the structure (CH3)3C-NH2. Here, the nitrogen is bonded to one carbon (tert-butyl group) and has two hydrogens. Therefore, it is a primary amine.

2. **Dimethyl amine**: The structure is (CH3)2-NH. Here, the nitrogen is bonded to two methyl groups and has one hydrogen. This makes it a secondary amine.

3. **Sec-butyl amine**: The structure is CH3-CH(NH2)-CH2-CH3. The nitrogen is bonded to one carbon and has two hydrogens, making it a primary amine.

4. **Isobutyl amine**: The structure is (CH3)2CH-CH2-NH2. The nitrogen is bonded to one carbon and has two hydrogens, classifying it as a primary amine.

### Step 3: Conclusion
From the analysis, the compound that is not a primary amine is **Dimethyl amine**, as it is a secondary amine.

### Final Answer:
**Dimethyl amine is not a primary amine.**

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