JEE Main Chemistry question

Which of the following has the maximum heat of hydrogenation? [Manipal 2008]

(A)A fully conjugated cyclic diene
(B)A partially conjugated (cross-conjugated) diene
(C)A diene with two isolated (non-conjugated) double bondsCorrect
(D)A single-ring compound with one double bond only

Answer: (C)

Solution

Conjugation stabilises a diene (lowers its ground-state energy), so a conjugated diene releases *less* heat on hydrogenation than an equal number of isolated double bonds would. Of

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Question ID VK-142317