The IUPAC name of the following compound is `CH_(2) = C = CH- CH_(3)`

Options

A. but-2,3-diene
B. but-1,2-diene
C. but-1-ene-2-yne
D. conjugated butadiene

Answer

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

### Step 1: Identify the longest carbon chain
The first step is to identify the longest continuous carbon chain in the compound. In this case, we have a chain of four carbon atoms:

```
C1 = CH₂
C2 = C
C3 = C
C4 = CH₃
```

### Step 2: Count the carbon atoms
Count the number of carbon atoms in the longest chain. Here, we have 4 carbon atoms.

### Step 3: Determine the parent name
Since there are 4 carbon atoms, the parent name will be based on butane. However, we need to consider the presence of double bonds.

### Step 4: Identify the double bonds
In the given compound, we see that there are two double bonds:
- One between C1 and C2
- Another between C2 and C3

### Step 5: Modify the parent name for double bonds
Since there are two double bonds, we will modify the parent name "butane" to "butadiene" (because "ane" is replaced with "adiene" for two double bonds).

### Step 6: Number the carbon chain
We need to number the carbon chain starting from the end closest to the first double bond. This gives us:
- C1 = C1 (double bond)
- C2 = C2 (double bond)
- C3 = C3
- C4 = C4

### Step 7: Indicate the positions of the double bonds
The double bonds are located between:
- C1 and C2 (1st position)
- C2 and C3 (2nd position)

Thus, we indicate the positions of the double bonds in the name as 1,2.

### Step 8: Combine the information
Combining all the information, we get the IUPAC name as "but-1,2-diene".

### Final Answer
The IUPAC name of the compound `CH₂ = C = CH - CH₃` is **but-1,2-diene**.

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