The structural formulas for isomeric diene hydrocarbons with composition C9H16 are:

1. 1,3-Butadiene: CH2=CH-CH=CH2

2. 1-Pentene: CH2=CH-CH2-CH2-CH3

3. 2-Pentene: CH2=CH-CH2-CH2-CH3

4. 1-Hexene: CH2=CH-CH2-CH2-CH2-CH3

5. 2-Hexene: CH2=CH-CH2-CH2-CH2-CH3

6. 3-Hexene: CH3-CH=CH-CH2-CH2-CH3

7. Cyclohexene: CH2=CH-CH2-C6H10

8. 1,4-Cyclohexadiene: CH2=CH-CH=CH-C6H8

9. 1,5-Cyclooctadiene: CH2=CH-CH2-C8H16

Each of these diene hydrocarbons can have different structural isomers based on the arrangement of the carbon-carbon double bonds.

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