Skript zum Praktikum Organische Chemie
Institut fr Pharmazie und Molekulare Biotechnologie Abteilung Chemie
3. Semester Studiengang Molekulare Biotechnologie
Praktikumsleiter: Valeska Dernedde email@example.com Salifu Seidu-Larry firstname.lastname@example.org
Begleitende Literatur zum Praktikum
1. http://www.ioc-praktikum.de/methoden/skript/Arbeitsmethoden.pdf Folgendes Kapitel ist obligatorisch durchzuarbeiten bis Beginn des Praktikums: Kapitel 2 Einleitung sowie 2.1 2.3 Folgende Kapitel werden als Grundlagenwissen zum prparativen Arbeiten sehr empfohlen und behandeln die im Laufe des Praktikums bentigten Arbeitstechniken: Kapitel 3 Einleitung sowie 3.1 und 3.4 Kapitel 5 Einleitung sowie 5.1 5.2 Kapitel 6 Einleitung sowie 6.1 6.2 Kapitel 8 Einleitung sowie 8.1 8.2 Kapitel 9 Einleitung sowie 9.1 9.3 ODER:
2. Organikum Folgendes Kapitel ist obligatorisch durchzuarbeiten bis Beginn des Praktikums: Kapitel 1: Hilfsmittel und Methoden zur Durchfhrung organisch-chemischer Reaktionen Folgende Kapitel werden als Grundlagenwissen zum prparativen Arbeiten sehr empfohlen und behandeln die im Laufe des Praktikums bentigten Arbeitstechniken: In Kapitel 2 und 3: Filtrieren, Kristallisieren, Extraktion von Flssigkeiten, Adsorptionschromatographie, Dnnschichtchromatographie, Schmelzpunktbestimmung, Polarimetrie. Bentigtes Material (mitzubringen von den Praktikumsteilnehmern)
Mo, 15.12.08 Di, 16.12. Mi, 17.12. Do, 18.12. Fr, 19.12.
Explanation 1st and 2nd
experiment Place assignment SR 25, INF 328
Mo, 12.01. Di, 13.01. Mi, 14.01. Do, 15.01. Fr, 16.01.
1st protocol due
Mo, 19.01. Di, 20.01 Mi, 21.01 Do, 22.01 Fr, 23.01
2nd protocol due
Mo, 26.01.08 Di, 27.01. Mi, 28.01. Do, 29.02. Fr, 30.01.
3rd protocol due
Mo, 02.02. Di, 03.02. Mi, 04.02. Do, 05.02. Fr, 06.02.
Test SR 20, INF 327
Introductory seminar: Monday, December 15th SR25 (INF 328) 13:30-15:30 Second seminar: Thursday, January 08th 2009, SR25 (INF 328) 13:30-15:30 Written test: Thursday, February 5th SR 20 (INF 327) 13:00-15:00 Second trial (Nachklausur): to be announced!
Experiment 1: Friedel-Crafts acylation of ferrocene.
Reaction: In a 100 mL, three-neck round-bottom flask equipped with a thermometer, a reflux
condenser and a drying tube are placed 2.0 g of ferrocene and 20 mL of acetic anhydride. The
mixture is stirred gently with a magnetic stirrer. 1 mL of phosphoric acid is added, and the
mixture is warmed up to 50 C until the solid dissolves completely (t=0). A small amount of
the mixture is then taken out and set aside. The temperature is increased to 100 C and the
reaction is left to react for 10 minutes at 100 C (analytical samples are taken at t=5 min, 10
min, then every 10 minutes), after which heating is interrupted. The advancement of the
reaction is checked by TLC (Silica gel F254, eluent: hexane/ethyl acetate, ratio to be
Work-up: The reaction mixture is then poured onto 50 g of crushed ice, the reaction flask
rinsed with a small amount of ice-cold water. The mixture is stirred for a few minutes with a
glass rod, and neutralized with a 3 N sodium hydroxide solution. The dark solid is collected
by vacuum filtration on a Bchner funnel (Bchnernutsche), washed several times with water
and allowed to dry on filter paper. The yield of crude product can then be determined.
Purification: Column chromatography
125 mg of crude reaction product are dissolved in 1 mL of dichloromethane and loaded on a
silica gel column (l=12 cm) conditioned with 9:1 hexane/diethylacetat. Elution is then
performed with hexane/ethyl acetate. The eluate is collected in fractions (~10 mL). The
fractions are controlled by TLC and those containing the clean product are pooled and the
solvent is removed under vacuum. The successful purification by column chromatography is
demonstrated by comparison with the crude product (before column) by means of TLC
Required characterizations: melting points of crude material and purified product.
Experiment 2: Synthesis of Bromocarvone (mixture of diastereoisomers)
5.0 g of R (-)-carvone are dissolved in 50 mL of methanol in a 100 ml round-bottomed flask
with a magnetic stirring bar. The solution is cooled to 0 C and 1.2 equivalents of
N-bromosuccinimide are added. The mixture is stirred for 20 min at 0 C and then allowed to
reach room temperature. The progress of the reaction is followed by TLC (1st sample after 30
min and then every 30 min, hexane: ethylacetate 80:20). After disappearance of carvone (~ 2
h) the solution is concentrated with a rotary evaporator (100 80 mbar) and the oily residue is
dissolved in 50 mL diethylether and 50 mL of 0.5 M NaOH. The mixture is transferred into a
separatory funnel with additional 30 mL of diethylether, and the two phases are separated.
The organic phase is then washed with 0.5 M NaOH (240 mL) and brine (220 mL) and
finally dried over Na2SO4 . The drying agent is filtered away and the solvent is removed under
vacuum (rotary evaporator).
Required characterizations: purity is controlled by TLC (hexane: ethyl acetate 80:20).
Experiment 3: Synthesis of benzyloxycarbonyl-L-leucyl-glycine ethyl ester
O H3N COO-
In a three-neck 100 ml round-bottom flask with a magnetic stirring bar and a thermometer is
placed L-leucine (4.0 g, 0.03 mol) and 9.0 mL of water. The suspension is cooled in an ice-
water bath and 5 M NaOH (6.0 mL) is added, giving a clear solution. The temperature of the
solution is allowed to equilibrate (10 min) before benzylchloroformate (5.92 g 5.0 mL,
0.033 mol) and 2 M NaOH (16.5 mL, 0.033 mol) are added in ten portions, alternatingly,
while the mixture is vigorously stirred and its temperature maintained at about 10 C. The
additions are completed in about 1.5 h. After continued stirring at room temperature for 30
min the pH of the mixture is adjusted to 10 with 2 M NaOH and the solution is extracted with
ether (415 ml). The aqueous layer is then acidified to pH 1-2 with 5 M HCl (about 6-7 ml)
and the oil which separates is extracted into diethyl ether (320 ml). The combined organic
layers are dried over Na2SO4, filtered and the solvent is removed under vacuum. The residual
syrup is used as such for the subsequent step.
Required characterizations: purity is controlled by TLC (CHCl3: EtOH 95:5 stain the plate
1 Blue-shift is a general purpose visualization reagent for TLC. It is prepared from 1 g Ce(SO4)2, 21 g molybdatophosphoric acid, 500 mL water, 31 mL conc. H2SO4. The obtained yellow solution is stored protected from light at 4C.
In a three-necked 100 mL flask equipped with thermometer, a rather big magnetic stirring bar,
and a CaCl2 drying tube a solution of Cbz-Leu-OH (from step 1) (2.65 g, 10 mmol) and
triethylamine in a 1:1 mixture of toluene and chloroform (25 mL) is cooled to -5 Cl.
Isovaleryl chloride (1.27 mL, 10 mmol) is added and the mixture is maintained at -5 C for
1.5 h for the formation of the mixed anhydride. In a separate flask a solution of glycine ethyl
ester hydrochloride (1.47 g, 10.5 mmol) and triethylamine (10.5 mmol) in 25 ml of
chloroform is prepared. This solution is cooled to -5 C just before addition to the mixed
anhydride reaction mixture and the reaction is continued allowing the temperature to rise to 0
C. The progress of the reaction is followed by TLC (1st sample after 30 min and then every
hour,2 CHCl3 : EtOH 9:1, stain the plate with blue-shift). After disappearance of the starting
Cbz-Leu-OH, the solution is washed with 50 mL portions of 10% KHSO4 (twice), water, 0.5
M NaHCO3 (twice) and water again and finally dried over Na2SO4. The drying agent is
filtered away and the solution is concentrated under vacuum to approximately one fourth. On
dilution with hexane (75 mL) the product separates in crystalline form. It is collected by
filtration, washed with hexane and shortly dried in air. The crude dipeptide is dissolved in
boiling ethanol and diluted with warm water until turbid. On cooling, crystals separate.
After several hours at room temperature the product is collected by filtration, washed with a
small amount of 1:1 ethanol/water mixtu