Alkene combustion and hydrogen addition

Burning alkenes

Alkenes burn in oxygen and release energy. With enough oxygen, complete combustion forms carbon dioxide and water. For ethene, the balanced equation is C₂H₄ + 3O₂ → 2CO₂ + 2H₂O. Alkenes often burn with smoky flames in air because combustion is incomplete. The smoke contains tiny carbon particles; incomplete combustion can also produce poisonous carbon monoxide.