How many tetramethyl benzene are possible:

Answer

To determine how many tetramethylbenzene isomers are possible, we can follow these steps:

### Step 1: Understand the Structure of Benzene
Benzene is a six-membered carbon ring with alternating double bonds. The basic structure can be represented as follows:

```
C
/ \
C C
| |
C C
\ /
C
```

### Step 2: Identify Positions for Methyl Groups
We need to add four methyl (–CH₃) groups to the benzene ring. The positions on the benzene ring are numbered as follows:

```
1
/ \
6 2
| |
5 3
\ /
4
```

### Step 3: Determine Possible Isomers
1. **All four methyl groups on adjacent carbons**: This configuration places all four methyl groups on carbons 1, 2, 3, and 4. This is the first isomer: **1,2,3,4-tetramethylbenzene**.

2. **Three methyl groups adjacent, one opposite**: Place three methyl groups on carbons 1, 2, and 3, and the fourth on carbon 5. This is the second isomer: **1,2,3,5-tetramethylbenzene**.

3. **Two pairs of methyl groups opposite each other**: Place two methyl groups on carbons 1 and 4, and the other two on carbons 2 and 5. This is the third isomer: **1,2,4,5-tetramethylbenzene**.

### Step 4: Count the Isomers
From the configurations above, we have identified three distinct isomers:
1. 1,2,3,4-tetramethylbenzene
2. 1,2,3,5-tetramethylbenzene
3. 1,2,4,5-tetramethylbenzene

### Conclusion
Thus, the total number of tetramethylbenzene isomers possible is **3**.

---