Experiment 4 - Hydroxybromination of Indene - Structural Analysis
by NMR
Objective:
In this lab, we will use indeneas the alkene starting material and perform a
hydroxybromination reaction. We will then perform a detailed NMR analysis to see
the product structure and we will use 1H NMR in the analysis to determine the
coupling constants and to analyze the complex coupling patterns.
Chemical Table:
Name Formula Mol Eq Mw mmol Amount
Indene C9H8 1.00 116 1.990mm 0.232g
g/mol ol
Ammoniu NH4Br 1.100 97.94 2.195mm 215mg =
m g/mol ol 0.215g
Bromide
OxoneTM** K5H3S4O18 1.116 614.78 2.212mm 1.36 g
g/mol ol
1:1 ---- ---- ---- ---- 10 mL
CH3CN:wate
r
product C9H8Br(OH) 1.00 212.90 1.999mm 0.424 g
g/mol ol
, Safety and Preparedness:
1. Describe a major risk that is associated with oxone, and the precautions
you will take while handling it.
Oxone is an oxidizer, contact between oxone and combustible materials can
cause a fire. It also causes burns on any exposed skin. For handling, use a
chemical fume hood, wear protective equipment, do not get in eyes, skin, or
on clothes because clothes are combustible.
2. You are not going to use an NMR spectrometer yourself, but it is important to
know about the risks. If you had a pacemaker, what precautions should you
take when near an NMR spectrometer?
Pacemakers are ferromagnetic, so an NMR spectrometer could alter or stop
the pacemaker entirely, leading to cardiac arrest or other heart
complications that can lead to death. If I had a pacemaker, I would stay
outside the NMR magnet room and consult with the NMR facility till I can
enter safely.
Experimental Procedure:
Reaction Setup
1. add 233 μL of indene and 10 mL of a 1:1 mixture of acetonitrile and
water to 50 mL round bottom flask equipped with a magnetic spin bar
2. add 215 mg of ammonium bromide and 1.36 g of oxone (ammonium
bromide is hygroscopic, cap reagent bottle when finished weighing
out)
3. Let reaction stir for 2 min at room temperature, (reaction mixture will
change color from orange, to yellow, to a very faint yellow.
Color changed from white to yellow, then back to white.
Isolation of Product
4. After 2 min, filter off the precipitate by vacuum filtration.
5. Pour filtrate into round bottom flask and remove acetonitrile by rotary
evaporation (when volume has decreased to half, acetonitrile should be
gone and should see solid present in your flask, which is insoluble)
Acetonitrile boiling point is 83 degrees C and water boiling point is 100 degrees C.
6. Add 5 mL of water to aid in precipitating out product
7. Filter off the white solid by vacuum filtration and allow to dry under vacuum
for 5-10 min Purification by Recrystallization
8. Purify product by recrystallization.
9. Dissolve product in a minimal amount of hot ethanol (~1 mL should be sufficient)
10.allow to cool slowly to room temperature.
11.Collect product by vacuum
filtration. Characterization
12.Weigh purified product to determine yield and obtain
melting point 0.1598g
Final yield = 160mg
Melting point = 126-129 degrees C
13.Compare observed melting point to literature value
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