The IUPAC name of the compound ` CH_2 = CH - CH(CH_3)_2` is :

Options

A. 1, 1-Dimethylprop-2-ene
B. 3-Methylbut-1-ene
C. 2-Vinyl propane
D. none of these

Explanation

To determine the IUPAC name of the compound \( CH_2 = CH - CH(CH_3)_2 \), we can follow these steps:

### Step 1: Identify the Longest Carbon Chain
First, we need to identify the longest continuous carbon chain in the compound. The structure can be visualized as follows:

- The compound has a double bond between the first and second carbon atoms.
- The third carbon atom has two methyl groups attached to it.

The longest carbon chain consists of four carbon atoms, which can be represented as:

\[ CH_2 = CH - CH - CH_3 \]

### Step 2: Number the Carbon Atoms
Next, we need to number the carbon atoms in the longest chain. According to IUPAC rules, we should give priority to the double bond by numbering the chain from the end closest to the double bond.

1. Start numbering from the left:
- Carbon 1: \( CH_2 \) (double bond)
- Carbon 2: \( CH \) (double bond)
- Carbon 3: \( CH \) (with two \( CH_3 \) groups)
- Carbon 4: \( CH_3 \)

This gives us the following numbering:
- C1 = \( CH_2 \)
- C2 = \( CH \)
- C3 = \( CH(CH_3)_2 \)
- C4 = \( CH_3 \)

### Step 3: Identify Substituents
Now, we need to identify any substituents attached to the main carbon chain. In this case, on the third carbon (C3), there are two methyl groups (–CH3).

### Step 4: Write the Name of the Compound
According to the IUPAC naming conventions:
- The parent chain has 4 carbon atoms, which corresponds to "butane."
- There is a double bond starting at carbon 1, so we use "but-1-ene."
- The substituent is a methyl group on carbon 3, which we denote as "3-methyl."

Putting it all together, the IUPAC name of the compound is:

**3-methylbut-1-ene**

### Final Answer
The IUPAC name of the compound \( CH_2 = CH - CH(CH_3)_2 \) is **3-methylbut-1-ene**.

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