|Alpha-Pinene with Iodine|
Alpha-pinene is an organic compound of the terpene class, found in turpentine oil of pine trees. Structure of this strained alkene with reactive four-membered ring is shown bellow:
When turpentine or alpha-pinene is poured over powdered iodine a very intensive emission of violet iodine vapors occurs. Step back immediately, because iodine and its vapors are harmful, so the experiment must be performed within a fume hood or in a place with adequate and strong ventilation or an open space.
As it can be seen, the system contains a four membered ring, and is therefore under tension. It is relieved of tension by a rearrangement, during which a norbornane derivate is formed (bicyclo[2.2.1.]heptane):
A great deal of energy from relief of ring strain in the alpha-pinene molecule is liberated during this rearrangement, and this leads to immediate iodine sublimation.