Question

Which from following structures represents 1,3 butadiene ?

• A.

  

• B.

  

• C.

  

• D.

  

Hint:

1,3-Butadiene has four carbons with double bonds starting at C1 and C3.

Answer 1

The Correct Option is B

Step 1: Write the target
The target is $\text{CH}_2=\text{CH}-\text{CH}=\text{CH}_2$: four carbons, two C=C bonds, separated by one single bond (a conjugated diene).

Step 2: Count in each drawing
Draw (A): about five carbons and a single double bond, so it cannot be a butadiene. Draw (B): four carbons with two double bonds, one at each end. Draws (C) and (D): the multiple line symbol is a triple bond, which belongs to an alkyne.

Step 3: Match
Only drawing (B) has two double bonds in the 1,3 positions of a four-carbon chain.

Step 4: Result
The answer is option (B).

Final Answer:
The conjugated four-carbon diene is option (B). This is option (B). \[ \boxed{\text{(B) }\text{CH}_2=\text{CH}-\text{CH}=\text{CH}_2} \]