The Department of Chemistry at the University of Illinois
The Chemistry learning center
Addition of bromine to hydrocarbons
Does liquid bromine react with either cyclohexane or cyclohexene?
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The glass on the left contains cyclohexane, an alkane with the formula C6H12. The glass on the right contains cyclohexene, an alkene which has the formula C6H10. |
Click on the small picture to see the video.
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An addition reaction occurs when halogens are added to alkenes, but not to alkanes. The following reaction occurs when Br2 is added to cyclohexene: One bromine atom adds to each side of the double bond, which opens to form two new single bonds. You can see the reaction occur because the red color of Br2disappears as it forms the colorless alkyl halide. |
Bromine is not able to react with cyclohexane by substitution, and there are no double bonds for an addition reaction, so no reaction occurs:
C6H12 + Br2 ----> N.R.
You can tell that no reaction has occurred because the red color of Br2 remains.
