Which of the following dienes contain conjugated double bonds?

• A. ${\mathrm{CH}}_2=\mathrm{CH}-\mathrm{CH}=\mathrm{CH}$₂
• B. $\mathrm{CH}$₃-CH=CH-CH=CH₂
• C. $\mathrm{CH}$₃-CH=CH-CH2-CH=CH₂
• D. ${\mathrm{CH}}_2=\mathrm{CH}-{\mathrm{CH}}_2-\mathrm{CH}=\mathrm{CH}$₂

Answer: (B)

Verified step by step guidance

1. Understand that conjugated dienes have alternating single and double bonds, allowing for overlap of p-orbitals and delocalization of electrons.
2. Examine each diene structure to identify the pattern of double and single bonds between the carbon atoms.
3. For the first diene, check if the double bonds are separated by exactly one single bond, which indicates conjugation.
4. For the second diene, similarly verify if the double bonds are conjugated by looking for alternating double and single bonds.
5. For the third and fourth dienes, identify if there is a methylene (-CH2-) group interrupting the conjugation, which would mean the double bonds are not conjugated.