Question

Question: Which of the following species are conjugated?

a.

b.

c.

d.

e.

Short answer

Answer

a. The given diene is conjugated.

b. The given diene is not conjugated.

c. The given diene is conjugated.

d. The given diene is conjugated.

e. The given diene is not conjugated.

Step-by-step solution

Dienes

Dienes can be conjugated and unconjugated. An example of a conjugated diene is 3,5-octadiene.

Conjugation

The overlap of p-orbital with three or more adjacent carbon atoms leads to conjugation. An example of a conjugated system is allylic carbocation.

Identification of conjugated diene

a. The given diene is conjugated as the bond present in it is separated by a single bond.

b. The given diene is not conjugated as two single bonds are present between two double bonds.

c. The given diene is conjugated as three adjacent carbon atoms are sp² hybridized and they contain an unhybridized p orbital.

d. Three adjacent carbon atoms are sp² hybridized and they possess an unhybridized p orbital. Hence, this compound is a conjugated diene.

e. The third carbon atom adjacent to the double bond is not sp² hybridized. Hence, this compound is not a conjugated diene.