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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 C6 H10.
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Click on the
small picture to see the video
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Video
for Windows
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Quicktime
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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:
C6H10
+ Br2 ----> C6H10Br2
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 Br2 disappears as it forms the colorless
alkyl halide.
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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.
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