The names of some compounds are given. Which one not in the `IUPAC` system?

Options

A. `{:(" "CH_3),(" "|),(CH_3CH_2-CH_2-CH-CH-CH_2CH_3),(" "|),(" "CH_2CH_3),(" 3- methyl-4-ethlheptane"):}`
B. `{:(CH_3-CH-CH-CH_3),(" | |"),(" OH " CH_3),(" 3-methyl - 2 - butanol"):}`
C. `{:(CH_3-CH_2-C-CH-CH_3),(" || |"),(" " CH_2CH_3),(" 2-ethyl - 3 -methylbut -1-ene"):}`
D. `{:(CH_3-C-=C-CH(CH_3)_2),(" 4- methyl-2-pentyne"):}`

Answer

To determine which of the given compound names is not in the IUPAC system, we will analyze each compound name step by step.

### Step 1: Identify the Compounds
Let's assume the compounds are labeled as follows:
1. Compound A
2. Compound B
3. Compound C
4. Compound D

### Step 2: Analyze Each Compound Name

#### Compound A
1. Identify the longest carbon chain.
2. Count the number of carbon atoms.
3. Identify any substituents (like methyl or ethyl groups).
4. Determine the correct IUPAC name based on the position of substituents and the type of carbon-carbon bonds.

**Analysis**:
- Longest chain: 7 carbons (heptane).
- Substituents: Methyl and Ethyl.
- Correct IUPAC name: 3-methyl-4-ethylheptane.

#### Compound B
1. Identify the longest carbon chain.
2. Check for functional groups (like -OH for alcohol).
3. Number the chain to give the lowest numbers to the functional groups.
4. Write the correct IUPAC name.

**Analysis**:
- Longest chain: 4 carbons (butane).
- Functional group: OH (alcohol).
- Correct IUPAC name: 3-methylbutan-2-ol.

#### Compound C
1. Identify the longest carbon chain.
2. Check for double bonds.
3. Number the chain to give the double bond the lowest number.
4. Write the correct IUPAC name.

**Analysis**:
- Longest chain: 5 carbons (pentene).
- Double bond present.
- Correct IUPAC name: 2,3-dimethylpent-1-ene.

#### Compound D
1. Identify the longest carbon chain.
2. Check for triple bonds.
3. Number the chain to give the triple bond the lowest number.
4. Write the correct IUPAC name.

**Analysis**:
- Longest chain: 5 carbons (pentane).
- Triple bond present.
- Correct IUPAC name: 4-methyl-2-pentyne.

### Step 3: Compare with Given Names
Now, we compare the analyzed IUPAC names with the provided names of the compounds.

- If any of the compound names do not match the correct IUPAC naming conventions, that is the answer.

### Conclusion
Based on the analysis, the compound that does not conform to the IUPAC naming system is **Compound C** with the name "2-ethyl-3-methylbut-1-ene", which is incorrect as per IUPAC rules.

### Final Answer
**The compound name that is not in the IUPAC system is Compound C.**

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