Electrophilic Aromatic Bromination Organic Chemistry Worksheet

Name:Exp #
Date:
Lab Partner
Diels-Alder reaction. Experiments 5&6
1. Abstract and Purpose: (2 point).
The Diels-Alder reaction is one of the most used reaction nowadays in organic chemistry, being a
reaction in which a diene reacts with a dienophile to form an adduct usually in the form of a sixmembered ring. It is a [4+2] cycloaddition reaction between a conjugated alkene called diene and a
substituted alkene or even an alkyne called the dienophile. The reaction is favored when the diene
possesses electron-donor groups whilst the dienophile contains electron-withdrawing groups since
in the reaction mechanism the electrons flow from the first to the latter in a concerted pericyclic
reaction in a single and cyclic transition step. In this laboratory session, a Diels-Alder reaction will
be conducted between one of the following dienes: a-phellandrene, a-terpinene or eucalyptus oil,
and maleic anhydride.
2. Balanced equation: (2 point)
Diene
(electron-rich
species)
Dienophile
(electrondefficient
species)
Diels-Alder adduct
Name:
Exp #
Date:
Lab Partner
3. Reagent Table (Add more rows when needed) (3 points)
Name
M.W.
(g/mol)
Density*
(g/mL)
M.P.*
(°C)
α-phellandrene
136.23
0.85
N/A
α-terpinene
136.23
0.84
Eucalyptus oil
–
Maleic
anhydride
98.06
B.P.*
(°C)
Amount
(grams
or mL)
Moles
Hazards/Precautions
171.5
–
6
mmol
N/A
173-175
–
6
mmol
–
–
–
2 mL
–
–
52-54
–
–
4
mmol
Flammable. Highly
poisonous if ingested.
Skin and eye irritating
Flammable. Highly
poisonous if ingested.
Skin and eye irritating
Flammable. Highly
poisonous if ingested.
Skin and eye
irritating.
Skin and eye
irritating.
4. Calculations: Shown each calculation for moles of reagents, limiting reagent, theoretical yield
and percent yield. (4 points)
Calculating moles of reagents:
2 mL of eucalyptus oil – undeterminable moles
6 mmol α-phellandrene
6 mmol α-terpinene
Determining limiting reagent:
6 mmoles of diene and 4 mmol of dienophile (maleic anhydride). Since the reaction is 1:1, the
excess reagent is the diene
The limiting reagent is maleic anhydride
Calculating theoretical yield:
Name:
Exp #
Date:
Lab Partner
The theoretical yield is
The actual yield is
Calculating Percent yield:
Reaction percent yield is
5. Procedure, Observations and Data
Procedure (4 point)
•
4 mmol of maleic anhydride and 6 mmol of
the assigned diene are transferred to a 25 mL
round-bottom flask.
•
5 mL of anhydrous diethyl ether are added to
the flask as a solvent along with 3 boiling
chips.
•
A reflux setup is assembled by attaching a
condenser and heating carefully to reflux
temperature for 45 minutes.
•
Once the reaction time is finished, it is
transferred to a small beaker while it is still
warm and covered with a glass watch.
•
Then, it is cooled down on ice, and the
formed precipitate collected under vacuum
Observations and Lab Data (4 point)
Name:
Exp #
Lab Partner
filtration washing the product with cold
petroleum ether
•
The product is then recrystallized form
isopropanol and dry under vacuum for
around 5 minutes to eliminate as most of the
solvent as possible and then dried in an oven
at 75°C.
•
An IR spectrum of the dry sample is obtained
a mixed melting point is determined 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.
Date:
Name:
Exp #
Date:
Lab Partner
•
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)
Name:
Exp #
Lab Partner
9. Image of your lab notebook. (3 point)
I reserve the right to modify points on this template at any time.
Date:
The spectrum below is the 1HNMR of the Diels-Alder adduct of Eucalyptus oil and malic anhydride. Please use this NMR spectrum to
support your conclusion of whether the diene in Eucalyptus oil is α-phellandrene or α-terpinene.