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Expt #4. Reaction of 3-Hexene with
Br2/H2O
References
(1) Porter,
D. J.; Stewart, A. T.; Wigal, C. T. J. Chem.
Educ. 1995, 72, 1039-1040.
(2) Mohrig, Techniques in Organic Chemistry, Chapter
20
Overview
In this lab you will carry out the
reaction of 3-hexene with N-bromosuccinimide
(NBS) and water to form 4-bromo-3-hexanol. (NBS
serves as a source of Br2.) You
will be assigned either trans-3-hexene or cis-3-hexene
as your starting material and determine the
stereochemistry of the obtained products using NMR.
Data sharing with a group that starts with the other
stereoisomer of 3-hexene will allow the determination
of the stereospecificity of the reaction.
Procedure
The procedures are
identical to those described in reference 1 except for
using 3-hexene instead of
1-methylcyclohexene as the starting alkene. Plan on
using same number of moles of 3-hexene as the
reference paper uses of their alkene.
Characterization
of Product
Determine the yield and obtain the proton NMR and IR
spectrum of your final product. See Chapter 20
(especially 20.3-5) in Mohrig for procedures involved
in obtaining an IR spectrum. One group will be asked
to obtain a C-13 NMR spectrum of their product to be
shared with the rest of the lab.
Post Lab:
Report not
only your results but also the results of another
lab group that ran the other stereoisomer of
3-hexene. By comparing the C-13 NMRs of the
two products you should be able to determine the
relative amounts of the two possible diasteromers that
could be formed. The results should be compared to the
prediction afforded by the accepted mechanism.
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