Which of the following is a `3^(@)` amine

Options

A. 1-methylcyclohexylamine
B. Triethylamine
C. Tert-butylamine
D. Propan-2-amine

Explanation

To determine which of the given compounds is a tertiary amine, we need to analyze the structure of each option and identify the number of alkyl groups attached to the nitrogen atom.

### Step-by-Step Solution:

1. **Understand the Definition of Amines:**
- Amines are classified based on the number of alkyl groups attached to the nitrogen atom:
- **Primary amine:** One alkyl group attached to nitrogen.
- **Secondary amine:** Two alkyl groups attached to nitrogen.
- **Tertiary amine:** Three alkyl groups attached to nitrogen.

2. **Analyze Each Option:**
- **Option 1: 1-Methylcyclohexyl amine**
- Structure: Cyclohexyl ring with a methyl group and an amine group (NH2).
- Analysis: The nitrogen is attached to one carbon from the cyclohexyl ring and one from the methyl group (total of 2 alkyl groups). Thus, this is a **secondary amine**.

- **Option 2: Triethyl amine**
- Structure: Nitrogen atom bonded to three ethyl groups (C2H5).
- Analysis: The nitrogen is attached to three ethyl groups (total of 3 alkyl groups). Thus, this is a **tertiary amine**.

- **Option 3: Tertiary butyl amine**
- Structure: Nitrogen atom bonded to a tertiary butyl group (C(CH3)3) and one hydrogen (NH2).
- Analysis: The nitrogen is attached to one tertiary butyl group and one hydrogen (total of 1 alkyl group). Thus, this is a **primary amine**.

- **Option 4: Propen-2-amine**
- Structure: An amine group attached to a propene structure (CH3-CH=CH-NH2).
- Analysis: The nitrogen is attached to one carbon from the propene structure (total of 1 alkyl group). Thus, this is a **primary amine**.

3. **Conclusion:**
- After analyzing all options, the only compound that qualifies as a tertiary amine is **Option 2: Triethyl amine**.

### Final Answer:
The correct answer is **Option 2: Triethyl amine**.