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

Options

A. 1,1-dimethyl-but-2-ene
B. 3-methyl-but-1-ene
C. 2-vinyl propane
D. None of the above

Answer

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

### Step 1: Identify the longest carbon chain
The first step in naming an organic compound is to identify the longest continuous carbon chain that includes the double bond. In this case, we can see that the longest chain consists of four carbon atoms.

### Step 2: Number the carbon chain
Next, we need to number the carbon chain. We want to give the double bond the lowest possible number. Starting from the end of the chain closest to the double bond, we can number the carbons as follows:
1. C1: CH2
2. C2: CH
3. C3: CH
4. C4: CH3

### Step 3: Identify substituents
Now, we look for any substituents attached to the main carbon chain. In this case, there is a methyl group (–CH3) attached to the third carbon (C3).

### Step 4: Combine the names
Now we can combine the information we have gathered:
- The longest chain has 4 carbon atoms, which corresponds to "but".
- The double bond is located between C1 and C2, so we denote it as "1-ene".
- There is one methyl substituent on C3, which we denote as "3-methyl".

### Step 5: Write the final IUPAC name
Putting it all together, the IUPAC name of the compound is:
**3-methylbut-1-ene**

### Summary of the steps:
1. Identify the longest carbon chain.
2. Number the carbon chain to give the double bond the lowest number.
3. Identify any substituents and their positions.
4. Combine the names to form the IUPAC name.