Number of Acyclic bromoalkene from the molecular formula `C_4H_7Br` (Structural only)

Options

A. A. 6
B. B. 8
C. C. 7
D. D. 9

Answer

To determine the number of acyclic bromoalkenes from the molecular formula \( C_4H_7Br \), we will follow these steps:

### Step 1: Calculate the Degree of Unsaturation (DU)
The degree of unsaturation helps us understand how many rings or double bonds are present in the molecule. The formula for calculating DU is:

\[ \text{DU} = \frac{(2C + 2 + N - H - X)}{2} \]

Where:
- \( C \) = number of carbon atoms
- \( N \) = number of nitrogen atoms
- \( H \) = number of hydrogen atoms
- \( X \) = number of halogens (in this case, bromine)

For \( C_4H_7Br \):
- \( C = 4 \)
- \( H = 7 \)
- \( Br = 1 \)
- \( N = 0 \)

Substituting the values into the formula:

\[ \text{DU} = \frac{(2 \times 4 + 2 + 0 - 7 - 1)}{2} = \frac{(8 + 2 - 7 - 1)}{2} = \frac{2}{2} = 1 \]

### Step 2: Understand the Implication of DU
A DU of 1 indicates that there is either one double bond or one ring in the structure. Since we are looking for acyclic compounds, we will only consider the double bond.

### Step 3: Identify Possible Structures
We will now draw the possible acyclic bromoalkenes with the formula \( C_4H_7Br \). The general structure will include a double bond and a bromine atom.

1. **1-Bromobut-1-ene**: \( CH_2=CH-CH_2-CH_2Br \)
2. **2-Bromobut-1-ene**: \( CH_2=CH-CH(Br)-CH_3 \)
3. **1-Bromobut-2-ene**: \( CH_3-CH=CH-CH_2Br \)
4. **3-Bromobut-1-ene**: \( CH_2=CH-CH_2-CH(Br)-CH_3 \)
5. **2-Bromobut-2-ene**: \( CH_3-C(Br)=CH-CH_3 \)
6. **1-Bromo-2-methylpropene**: \( CH_2=CH-CH(CH_3)-Br \)
7. **2-Bromo-2-methylpropene**: \( C(Br)=C(CH_3)-CH_3 \)

### Step 4: Count the Isomers
After identifying the structures, we can count them:
1. 1-Bromobut-1-ene
2. 2-Bromobut-1-ene
3. 1-Bromobut-2-ene
4. 3-Bromobut-1-ene
5. 2-Bromobut-2-ene
6. 1-Bromo-2-methylpropene
7. 2-Bromo-2-methylpropene

Thus, the total number of acyclic bromoalkenes is **7**.

### Final Answer
The number of acyclic bromoalkenes from the molecular formula \( C_4H_7Br \) is **7**.

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