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| Addition of Iodine to Alpha-Pinene (Version 1) |
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Voiceover
Cyclohexene is added to iodine. When a-pinene is added to iodine a highly exothermic reaction occurs which causes unreacted iodine to sublime.
Discussion
Iodine does not react readily with most alkenes including cyclohexene but it reacts rapidly and highly exothermically with a-pinene. The exothermic nature of the reaction is attributed to the relief of ring strain from the rearrangement of the initial carbocation to the norbornyl carbocation with resulting shift from the strained cyclobutyl ring to the less strained cyclopentyl ring system. The heat of reaction causes the excess iodine to sublime as a purple cloud. The use of this reaction in disinfecting a wound on a horse's hoof was related by James Herriot in his book "All Creatures Great and Small."
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Citations:
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Kelly, T. Ross
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J. Chem. Educ. 1977, 54, p 228.
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Herriot, J.
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All Creatures Great and Small; Bantam Books: New York, 1972; pp 26-28.
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Design, Text and Demonstrator:
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Gary Trammell
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University of Illinois at Springfield, Springfield, IL 62794
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Videographer/Editor:
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Steve Dykema
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University of Illinois at Springfield, Springfield, IL 62794
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Voice:
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Margaret Biddle
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University of Wisconsin - Madison, Madison, WI 53706
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Audio Production:
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Greg Minix
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University of Wisconsin - Madison, College of Engineering, Madison, WI 53706
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Jerrold J. Jacobsen
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University of Wisconsin - Madison, Madison, WI 53706
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