Give the `IUPAC` name of the following compound.
`CH_(2) = CH - CH (CH_(3))_(2)`

Options

A. 1,1-Dimethylprop-2-ene
B. 3-Methylbut-1-ene
C. 2-Vinylpropane
D. 1-Isopropylethylene

Answer

To determine the IUPAC name of the compound `CH₂=CH-CH(CH₃)₂`, we will follow these steps:

### Step 1: Draw the Structure
First, we need to visualize the structure of the compound. The given formula can be represented as:
```
CH3
|
CH2=CH-CH
|
CH3
```
This shows that we have a double bond between the first two carbon atoms and a carbon atom with two methyl groups attached.

### Step 2: Identify the Longest Carbon Chain
Next, we identify the longest continuous carbon chain that includes the double bond. In this case, the longest chain consists of 4 carbon atoms:
- C1: CH₂ (part of the double bond)
- C2: CH (part of the double bond)
- C3: CH (with two methyl groups)
- C4: CH₃ (methyl group)

### Step 3: Number the Carbon Chain
We need to number the carbon chain starting from the end closest to the double bond. This gives us:
1. C1: CH₂
2. C2: CH
3. C3: CH (with two methyl groups)
4. C4: CH₃

### Step 4: Identify Substituents
In this structure, we have:
- A double bond between C1 and C2.
- A methyl group (−CH₃) attached to C3.

### Step 5: Assign the Position of the Double Bond
The double bond starts at C1, so we denote this as "but-1-ene" since there are 4 carbons in the longest chain (but-).

### Step 6: Combine the Information
Now, we can combine all the information:
- The longest chain is butane (4 carbons).
- The double bond is at position 1.
- There is a methyl group at position 3.

Thus, we write the name as "3-methylbut-1-ene".

### Final Answer
The IUPAC name of the compound `CH₂=CH-CH(CH₃)₂` is **3-methylbut-1-ene**.

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