How many isomeric amines with formula `C_(7)H_(9)N` contain a benzene ring ?

Options

A. 4
B. 5
C. 6
D. 7

Answer

To determine how many isomeric amines with the formula \( C_7H_9N \) contain a benzene ring, we can follow these steps:

### Step 1: Understand the Structure
The formula \( C_7H_9N \) indicates that we have 7 carbon atoms, 9 hydrogen atoms, and 1 nitrogen atom. Since we need to include a benzene ring, which consists of 6 carbon atoms, we will have 1 carbon atom remaining to attach to the benzene ring.

### Step 2: Identify Possible Structures
1. **Benzene Ring with an Amino Group**: The simplest structure is an aniline derivative where the amino group (\(-NH_2\)) is directly attached to the benzene ring.
- **Example**: \( C_6H_5NH_2 \) (Aniline)

2. **Substituted Anilines**: We can introduce a methyl group (\(-CH_3\)) as a substituent on the benzene ring. This gives us positional isomers:
- **Ortho (o-)**: \( C_6H_4(CH_3)NH_2 \) (o-Methylaniline)
- **Meta (m-)**: \( C_6H_4(CH_3)NH_2 \) (m-Methylaniline)
- **Para (p-)**: \( C_6H_4(CH_3)NH_2 \) (p-Methylaniline)

3. **Amino Group as a Side Chain**: We can also consider structures where the amino group is part of a side chain:
- **Benzylamine**: \( C_6H_5CH_2NH_2 \)
- **N-Methylbenzylamine**: \( C_6H_5CH_2N(CH_3) \) (Secondary amine)

### Step 3: List All Isomers
Now we can summarize the isomers:
1. Aniline (\( C_6H_5NH_2 \))
2. o-Methylaniline (\( C_6H_4(CH_3)NH_2 \))
3. m-Methylaniline (\( C_6H_4(CH_3)NH_2 \))
4. p-Methylaniline (\( C_6H_4(CH_3)NH_2 \))
5. Benzylamine (\( C_6H_5CH_2NH_2 \))
6. N-Methylbenzylamine (\( C_6H_5CH_2N(CH_3) \))

### Step 4: Count the Isomers
After listing the possible structures, we can count them:
- Aniline
- Ortho, Meta, and Para Methylaniline
- Benzylamine
- N-Methylbenzylamine

This gives us a total of **5 isomeric amines** that contain a benzene ring.

### Final Answer
Thus, the number of isomeric amines with the formula \( C_7H_9N \) that contain a benzene ring is **5**.

---