Manual - Preparatory Classes
Manual - Preparatory Classes
Manual - Preparatory Classes
Objectives:
to train basic organic laboratory techniques
to learn basic procedures for isolation and purification of organic compounds
to use acid-base chemistry for separation of organic compounds
Topics of study:
Suggested textbooks:
Extraction, filtration, melting-point determination:
J. W. Zubrick, The Organic Chem Lab Survival Manual: A Student's Guide to Techniques, Wiley,
eight edition, chapters: 12 (The melting-point experiment); 13 pages 107-110 (Gravity Filtration),
110-113 (The Büchner Funnel and Friends), 114-115 (The Water Aspirator: A Vacuum Source),
117-118 (Salting Out), 118-119 (World-Famous Fan-Folded Fluted Paper); 15 (Extraction and
washing) or
R. J. Fessenden, J. S. Fessenden, P. Feist, Organic Laboratory Techniques, Brooks/Cole Publishing
Company, third edition, chapters: Technique 2 (Melting Points), Technique 3 (Extraction)
Chemicals:
a sample of benzoic acid, m-nitroaniline sodium hydroxide
and naphthalene suspended in water anhydrous magnesium sulfate
diethyl ether brine
concentrated hydrochloric acid
Advanced organic chemistry – preparatory classes
Procedure:
1. Mount a metal ring to a laboratory stand. Make sure the size of the ring is adjusted to the size
of separating funnel. Place the separating funnel into the metal ring.
2. Place the sample of organic compounds suspended in water in the separating funnel.
3. Start pouring small portions (10 mL) of diethyl ether to the suspension until solids inside
separating funnel fully dissolves. Shake the suspension gently to facilitate the dissolution
process. Remember which layer (upper or lower) is diethyl ether.
4. Pour 10 mL of 3 M hydrochloric acid into the mixture in separating funnel and plug it with a
stopper. Shake the separating funnel vigorously for a while. Remember to equalize the pressure
couple times by slow opening of the stopcock. The amine was transformed into water-soluble
salt in the course of the reaction.
5. Mount the separating funnel into the metal ring, remove the stopper and wait until the
emulsion separate into two distinct layers.
6. Slowly open the stopcock and drain the lower layer into the beaker no. 1.
7. Pour 10 mL of distilled water into the solution in the separatory funnel and shake it for a while.
After the full separation of emulsion into two layers, drain the lower one into the beaker no. 1.
8. Pour 10 mL of 1.5 M NaOH into the mixture in separating funnel and plug it with a stopper.
Shake the separating funnel vigorously for a short time. Remember to equalize the pressure a
couple of times by slow opening of the stopcock. Repeat instructions from procedure 5. Organic
acid was transformed into water-soluble salt in the course of the reaction.
9. Slowly open the stopcock and drain the lower layer with sodium benzoate into the beaker no.
2.
10. Pour 10 mL of distilled water into the solution in the separatory funnel and shake it for a while.
After the full separation of emulsion into two layers, drain the lower one into the beaker no. 2.
11. Pour 10 mL of brine into the solution in the separatory funnel and shake it for a while. After the
full separation of emulsion into two layers, drain the lower one into the beaker no. 3 and the
upper one into the beaker no. 4.
Advanced organic chemistry – preparatory classes
12. Place one spatula of anhydrous magnesium sulfate into the beaker no. 4 and stir it for a while.
Place a watch glass on the top of the beaker.
13. To the solution in the beaker no. 1, add dropwise a concentrated solution of sodium hydroxide
until the pH of solution reaches a value of 10 – 11 (use universal indicator papers). Place the
beaker in the crystallizer filled with crushed ice until the solution is cooled down.
14. To the solution in the beaker no. 2, add dropwise a concentrated hydrochloric acid until the pH
of solution reaches a value 1 – 2 (use universal indicator papers). Place the beaker in the
crystallizer filled with crushed ice until the solution is cooled down.
15. Remove the drying agent from the beaker no. 4 using a gravity filtration technique. Transfer the
filtrate into small round-bottomed flask and evaporate the solvent using rotary evaporator.
Transfer the solid residue from the flask into the small vial and protect it with paper. Leave it to
dry in your locker until the next class.
16. Filter both precipitates from beakers no. 1 (m-nitroaniline) and 2 (benzoic acid) using a vacuum-
filtration technique and transfer them into two vials. Protect the vials with paper and leave it
until the next class. At this point, the solution from the beaker no. 3 may be removed.
17. Measure the melting points for all three substances you separated.
name
formula
Advanced organic chemistry – preparatory classes
description
mass
p.4
p.8
Advanced organic chemistry – preparatory classes
p.13
p.14
Advanced organic chemistry – preparatory classes
Objectives:
to synthesize aspirin – a physiologically active compound
to practice a simple synthetic and purification procedure
to confirm the identity of the compound using a simple analytical reaction
to determine purity of compound by melting point measurements and NMR technique
Topics of study:
Suggested textbooks:
Basic reactions of carboxylic acids, anhydrides and phenols
K. P. C. Vollhardt, N. E. Schore, Organic Chemistry: Structure and Function, W. H. Freeman
and Company, New York, fifth edition, chapters: 19-8 (Carboxylic Acid Derivatives), 19-13
(Biological Activity of Carboxylic Acids), 20-3 (Chemistry of Carboxylic Anhydrides), Chemical
Highlight 22-2 (Aspirin: A Phenyl Alkanoate Drug) or
J. McMurry, Fundamentals of organic chemistry, Brooks/Cole Publishing Company, fourth
edition, chapters: 8.8 (Synthesis and Reactions of Phenols), 10 (Carboxylic Acids and
Derivatives)
Synthetic procedure is based on: Vogel, A. I., A text-book of Practical Organic Chemistry
including qualitative organic analysis, third edition, 1956, Longman
Advanced organic chemistry – preparatory classes
Chemicals:
Synthetic procedure:
1. Warm the water bath to 60°C.
2. Place salicylic acid and acetic anhydride in a round-bottomed flask.
3. Add few drops of concentrated sulfuric acid to the mixture of reactants and rotate the flask
for a while.
4. Place the flask inside a water bath for 15 min. From time to time, stir the reagents using a
glass rod. Make sure the temperature of mixture is between 50 and 60°C.
5. Remove the flask from the water bath and leave it to cool down.
6. Add 150 mL of distilled water and vigorously stir the suspension.
7. Filter the crude product using a vacuum filtration technique.
8. Place a small portion of crude product into an open vial, protect it with a paper and leave it
to dry.
Recrystallization procedure:
1. Place the crude product inside a round-bottomed flask (250 mL) and add 30 mL of ethanol.
2. Mount the reflux condenser on the top of the flask and warm the mixture in a water bath till
solution.
3. Pour the solution into ca. 75 mL of hot water. If the product crystallized at this stage, you
should dissolve it one more time in water bath.
4. Leave the solution for slow cooling.
5. Filter the crude product using vacuum filtration technique.
6. Place the product into evaporator and protect it with paper assigned to you.
7. Place the evaporator with dry product into a desiccator and leave until the next class.
Advanced organic chemistry – preparatory classes
Reagents
name
density [g/ml]
mass/volume
Safety information
compound
Color after
addition of FeCl3
Description of product
mass [g]
Advanced organic chemistry – preparatory classes
yield [%]
Objectives:
to train basic organic laboratory techniques
to learn basic procedures for isolation and purification of organic compounds
Topics of study:
Suggested textbooks:
J. W. Zubrick, The Organic Chem Lab Survival Manual: A Student's Guide to Techniques, Wiley,
eight edition
R. J. Fessenden, J. S. Fessenden, P. Feist, Organic Laboratory Techniques, Brooks/Cole
Publishing Company, third edition
Chemicals:
glacial acetic acid (15 mL)
n-butanol (11.5 mL)
sulfuric acid (0.5 mL)
sodium hydrogen carbonate
anhydrous sodium sulfate
Advanced organic chemistry – preparatory classes
A direct reaction of acid with alcohol, leading to respective ester, proceeds according to the
following mechanism:
As one can notice esterification is an equilibrium reaction, thus to move equilibrium in the
product’s direction, one needs to remove the water or use an excess of one of the substrates.
Direct esterification is catalyzed by strong acids (see the mechanism) e.g. sulfuric, hydrochloric
or p-toluenosulfonic acids.
The experiment consists of a few stages:
Reflux of a substrates mixture
1. In a 100 mL round-bottom flask, mix together glacial acetic acid (15.0 mL), n-butanol (11.5
mL), and add 0.5 mL of concentrated sulfuric acid.
2. To prevent overheating, add a few boiling chips into the flask.
3. Prepare a setup for a reflux procedure. Turn on cooling water flow, connect your reaction flask
and turn the heating mantle on.
4. Allow the mixture to reflux for 30-60 min.
Simple distillation
1. After drying, filter the drying agent (you should wash it with a small amount of
dichloromethane) directly into a 50 mL distillation flask.
2. Add a few boiling chips.
3. Prepare a distillation apparatus, turn on the water flow and mount your distillation flask.
4. Slowly start to heat the mixture.
5. When it starts to boil, begin to collect of forerunning fraction until you achieve temperature
equal to the boiling point of ester.
6. Collect the main ester fraction, within a range of two Celsius degrees, to a weighed vessel.
Advanced organic chemistry – preparatory classes
7. Note all amounts and temperatures. Do not distill the mixture to dryness.
Equipment (part 1)
Equipment (part 2)
Advanced organic chemistry – preparatory classes
Name/formula
mass/volume [g or mL]
Density [g/mL]
Safety information
Calculations
Objectives:
to synthesize meso-tetraphenylporphyrin from pyrrole and benzaldehyde
to practice small-scale synthesis, thin-layer and column chromatography
Topics of study:
thin-layer chromatography
column chromatography
Suggested literature:
Synthesis of porphyrin
Lindsey, J. S., Hsu, H. C., Schreiman, I. C. Tetrahedron Lett. 1986, 27, 4969
Lindsey, J. S., Schreiman, I. C., Hsu, H. C., Kearney, P. C.; Marguerettaz, A. M. J. Org. Chem.
1987, 52, 827
Chromatographic techniques
J. W. Zubrick, The Organic Chem Lab Survival Manual: A Student's Guide to Techniques, Wiley,
eight edition, chapters: 21 (The rotary evaporator), 26 (Chromatography: some generalities),
27 (Thin-layer chromatography), 28 (Wet-column chromatography) or
R. J. Fessenden, J. S. Fessenden, P. Feist, Organic Laboratory Techniques, Brooks/Cole
Publishing Company, third edition, chapters: Technique 11 (Column Chromatography),
Technique 12 (Thin-layer Chromatography)
Chemicals:
solution of pyrrole in dichloromethane 2,3-dichloro-5,6-
(4.5 mL) dicyanobenzoquinone (DDQ) (171 mg)
solution of benzaldehyde in aluminium oxide (basic, grade II) for
dichloromethane (4.5 mL) chromatography
solution of boron trifluoride-diethyl ether dichloromethane for chromatography
complex in dichloromethane (1 mL) n-hexane for chromatography
Procedures:
Synthetic procedure:
1. Using 5 mL syringes, place solutions of pyrrole and benzaldehyde in 50 mL round-bottomed
flask equipped with a magnetic stirring bar (Figure 1).
2. Flush the solution with nitrogen for 15 min.
3. Put the rubber septum at the top of flask neck and protect the mixture from air using a
nitrogen-filled balloon. Cover the flask with aluminum foil to protect reagents from light
(Figure 2).
4. Using 1 mL syringe, place a solution of boron trifluoride-diethyl etherate in the flask.
5. Mix the reagents for 1 h using a magnetic stirrer.
6. Remove the balloon with septum and add DDQ to the solution.
7. Evaporate the solvent under reduced pressure using rotary evaporator.
8. Prepare the second TLC chamber in the same manner using n-hexane (eluent 2).
9. Put TLC plates into TLC chambers. Be careful – it is very easy to break the adsorbent layer.
You can help yourself by using tweezers (Figure 3).
10. Put a watch glass on the top of a beaker and observe the separation (Figure 4).
11. Once the eluent reach the level 1 cm below the upper edge, take out the plate from the TLC
chamber and mark the solvent line using a pencil.
12. Leave plates for a couple minutes to dry.
13. Put the plates under the UV-lamp and using a pencil, mark
the spots which appeared after the separation (Figure 5).
14. Measure the distance between start line and finish line and
between the start line and the center of each spot after
separation. Calculate the Rf for each spot using the formula:
a
R f (Figure 5).
b
15. Repeat your calculations for the plate developed in the eluent 2. Compare the results.
Synthesis of porphyrin
Observations and conclusions
Column chromatography
Observations and conclusions
Thin-layer chromatography
Eluent 1
Observations and conclusions
Advanced organic chemistry – preparatory classes
Rf calculations
Eluent 2
Observations and conclusions
Rf calculations