Which of the following diketones has all its carbon atoms sp^2 hybridized and forms a continuous conjugated system?

Step-by-step solution

To determine the correct molecule, we must check both for conjugation and the hybridization of every carbon atom. Hex-3-ene-2,5-dione: CH₃-C(=O)-CH=CH-C(=O)-CH₃ . While the central core is conjugated, the two terminal methyl ( CH₃ ) groups contain sp^3 hybridized carbon atoms. Cyclohex-2-ene-1,4-dione: Contains a conjugated system involving one C=C bond and two C=O bonds, but the ring also contains two sp^3 hybridized CH₂ groups at positions 5 and 6. Cyclopent-4-ene-1,3-dione: Contains a C=C bond and two C=O bonds.