Organic Chemistry II Lab

Name:Exp #
Date:
Lab Partner
Polimerization of stryene
1. Abstract and Purpose: (2 point).
Polymers are chemical species formed by the union of numerous simple and repeating structural
units called monomers, making them very “heavy” in terms of their molar masses. There are two
commonly known methods to convert these monomers into polymers: step-growth polymerization
and chain-reaction polymerization. In the first, the monomers react with each other to form longer
chains without the aid of an external catalyst in a sort of spontaneous reaction. This polymerization
often occurs in activated aromatic compounds such as aromatic amines forming very long chains of
aromatic rings in a tar-like oil. On the other hand, in the chain-polymerization reactions, an initiating
agent (anion, cation, or free radical) is added to the monomers creating a very reactive species that
induces condensation between the monomers. The overall mechanism consists of three steps:
initiation, propagation, and termination.
The purpose of this lab is to synthesize polystyrene from the polymerization reaction of styrene by
means of a free radical, using t-butylperoxybenzoate as the initiating agent and xylene as the solvent.
The reaction will be carried out at reflux temperature and collected in methanol.
2. Balanced equation: (2 point)
t-butylperoxybenzoate (cat.)
Name:
Exp #
Date:
Lab Partner
3. Reagent Table (Add more rows when needed) (3 points)
M.W.
(g/mol
)
Name
Density
*
(g/mL)
M.P.*
(°C)
B.P.*
(°C)
Amount
(grams
or mL)
Moles
Styrene
104.2
0.906
-31
145
2 mL
0.0174
Xylene
106.2
0.86
-25
143
5 mL
solvent
tbutylperoxybenzoate
194.2
0.86
9-11
75-76
7 drops
Catalytic
amount
Methanol
32.0
0.792
-97.6
64.7
50 mL
solvent
Hazards/Precautions
Flammable, irritating
agent. Work under
hood
Flammable, irritating
agent. Work under
hood
Flammable, irritating
agent. Work under
hood
Flammable
4. Calculations: Shown each calculation for moles of reagents, limiting reagent, theoretical yield
and percent yield. (4 points)
Calculating moles of reagents:
•
Moles of styrene:
2 𝑚𝐿 ×
0.906 𝑔
1 𝑚𝑜𝑙
×
= 0.0174 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑠𝑡𝑦𝑟𝑒𝑛𝑒
1 𝑚𝐿
104.2 𝑔
There is only one reagent. The t-butylperoxybenzoate acts as a catalyst. Therefore, the
limitng reagent is the styrene itself.
•
Theoretical yield:
0.0174 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑠𝑡𝑦𝑟𝑒𝑛𝑒 ×
104.2 𝑔
= 1.812 𝑔𝑟𝑎𝑚𝑠 𝑝𝑜𝑙𝑦𝑠𝑡𝑦𝑟𝑒𝑛𝑒
1 𝑚𝑜𝑙
Name:
Exp #
Date:
Lab Partner
The actual yield is
Calculating Percent yield:
Reaction percent yield is
5. Procedure, Observations and Data
•
•
Procedure (4 point)
Observations and Lab Data (4 point)
2 mL of dry styrene, 5 mL of xylene, and 3 boiling
Report all observations and all data that you collect in
chips are added to a 25 mL round-bottom flask.
the lab here
To the mixture, 7 drops of t-butylperoxybenzoate are
added
•
The reaction mixture is heated at reflux temperature
and using a drying tube for around 20 minutes.
•
Once the reaction finished the mixture is poured in 50
mL of methanol and stirred until a white solid
precipitates.
•
The solid is collected by vacuum filtration and
weighed to determine its yield
Name:
Exp #
Lab Partner
6. Conclusions and discussions (4 points)
7. References: (1 point)
8. Image of your lab notebook. (3 point)
I reserve the right to modify points on this template at any time.
Date:
Title: Experiment 5&6 Diels-Adler Reaction
1. Abstract and Purpose: (2 point).
Otto Diels and Kurt Alder established the potent organic reaction known as the Diels-Alder
reaction in 1928. It creates a cyclohexene ring with well-defined regio- and stereochemistry by coupling
a conjugated s-cis diene with a substituted alkene, known as the dienophile. It absorbs heat to
accomplish the [4+2] cycloaddition reaction, which is typically carried out using an electron-rich diene
and an electron-poor dienophile in an organic solvent like toluene or ether. This lab purpose is to
develop our understanding in Diels- alder reaction. We will be conducting the experiment in three
groups which will be a-phellandrene, a-terpinene or eucalyptus oil.
2. Balanced equation: (2 point)
There are several free structure drawing programs available e.g. acdlabs.com. If you don’t have a
drawing program, hand draw the structures.
3. Reagent Table (Add more rows when needed) (3 points)
Name
M.W.
(g/mol)
Density*
(g/mL)
M.P.*
(°C)
a-phellandrene
136.23
0.85
Na
171.5
a-terpinene
136.23
g/mol
0.837
g/mL
NA
173-175
C
eucalyptus oil
B.P.*
(°C)
Amount
(grams
or mL)
Moles
Hazards/Precautions
Acute toxicity
Skin
corrosion/irritation
Serious eye damage
Germ cell
mutagenicity
Carcinogennicity
Acute toxicity
Acute toxicity
N.B. For solvents (like methanol) or drying agents (e.g. sodium sulfate), you don’t need to
calculate the moles.
* Report only when applicable
4. Calculations: Shown each calculation for moles of reagents, limiting reagent, theoretical yield and percent
yield. (4 points)
Calculating moles of reagents:
Determining limiting reagent:
The limiting reagent is
Calculating theoretical yield:
The theoretical yield is
The actual yield is
Calculating Percent yield:
Reaction percent yield is
5. Procedure, Observations and Data
Procedure (4 point)
A summary of the procedure done with bullet points)
(2 points)
-Procedure
Combine maleic anhydride (4 mmol), your assigned
diene (6.0 mmol) and 5 mL of anhydrous diethyl
ether into a tared 25 mL round bottom flask. For
eucalyptus oil, use 2 mL of the oil. Add 3 boiling
stones.
Caution: Diethyl ether is highly flammable! Maleic
anhydride is corrosive and toxic.
Attach a condenser to the round bottom flask. Be sure
the connection is tight. Gently
reflux the mixture over low steam for 45 minutes.
While it is warm, transfer the reaction mixture to a
small beaker, cover with a watch glass, and let cool
to room temperature. Cool it further on ice before
collecting the crystals by vacuum filtration. Wash the
crystals with 5 mL of cold petroleum ether.
Recrystallize the Diels-Alder product from
isopropanol. Add hot isopropanol until the material
Observations and Lab Data (4 point)
hhas dissolved. It may remain slightly cloudy. Cool
to room temperature to form crystals. Complete the
crystallization by placing the flask in ice. If crystals
do not form, scratch the bottom of the flask with a
glass rod and place in ice. Isolate the pure material
using the Hirsch funnel. Use some ice- cold
isopropanol to rinse all the crystals into the funnel.
Air dry on the funnel for 5 minutes by pulling air
through the solid using the vacuum. Transfer the
material to a watch glass and dry in the oven (75C).
Important! alcohol can cause the product to undergo
solvolysis, so it is important that you avoid prolonged
boiling during recrystallization.
Weigh the solid after drying and obtain a melting
point and infrared spectspectrum. In addition,
perform a mixed melting point in the following
manner: half the teams who used eucalyptus oil will
exchange about 25 mg of their product for about 25
mg of product from each team in the – phellandrene
group. The other half of the eucalyptus oil teams will
exchange with the -terpinene group. Combine the
product you obtained from the other group with an
equal amount of your product and grind them
together until they are mixed well. Perform a melting
point on the mixed material. If the two substances are
identical, there will be no change in the melting
point. If they are different substances, the melting
point will be depressed.
If you do not have a high field NMR available to
assess your sample, your instructor will provide the
NMR spectra of the two known Diels-Alder adducts
and the unknown from eucalyptus oil. Using your
data and the data generated by the other two teams in
your group, determine the unknown diene in
eucalyptus oil
6. Conclusions and discussions (4 points)
7. Post-lab Questions
1. Using curly arrows, give the electron flow for the Diels-Alder reaction performed in today’s lab.
8. References: (1 point)
9. Image of your lab notebook. (3 point)