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Prepform synthesis lab 1b experiment 4.1 part 1
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Synthesis lab 1b (MOL126)Preparation form experiment 4.1 (part one)
Lisa Verhoeven, s1014716
7-2-2022
Steam distillation of eugenol
from clove
Experimental aim
The aim of this experiment is to purify eugenol (4-allyl-2-methoxyphenol) from cloves by means of
steam distillation. Moreover, we aim to analyse the obtained product by means of GC-MS, FT-IR and
1
H-NMR spectroscopy.
Background
Eugenol (4-allyl-2-methoxyphenol) is an organic compound that is isolated from cloves, and is
frequently used in the perfume industry. Eugenol and its derivative acetyl eugenol form are the main
substances present in crude clove oil.
Eugenol has a boiling point of around 253 ◦C, which makes that normal distillation of eugenol from
clove would be unfeasible. Steam distillation is more suited for the distillation of eugenol, because
herein the eugenol forms a suspension with water. As a result of this poor miscibility, steam
distillation increases the vapour pressure of the eugenol-water mixture as the sum of the vapour
pressure of both immiscible substances – eugenol and water – such that it can be distilled at a
temperature around 100◦C. When steam distilling eugenol from cloves, one must obtain the distillate
in fractions because eugenol will end up in the distillate prior to acetyl eugenol, as acetyl eugenol has
a higher boiling point than eugenol.
The pKa of eugenol is ~10.2 at 25◦C. This is relevant when isolating eugenol from cloves because the
phase – aqueous or organic – in which eugenol will end up during extraction depends on if eugenol is
protonated or deprotonated, which in turn depends on its pK a and the pH of the solution. When
eugenol is deprotonated, it remains in the aqueous phase during extraction, whereas it will diffuse
into the organic phase when it is protonated.
Experimental
Isolation of eugenol from cloves
1. Build the steam distillation set up as shown in the lab notebook.
2. Place a suspension of crushed cloves (30 g) in hot water (~1 L) in the distillation flask of the
steam distillation setup depicted in figure 2.
3. Heat the boiler kettle until steam passes into the distillation flask. Control the heating so that
all steam condenses in the condenser.
4. Obtain the distillate in fractions.
5. Stop the distillation when no more milky distillate is obtained (~1.5 h).
6. Extract eugenol into the organic phase by using dichloromethane (DCM) (3x50 mL).
7. Wash the combined organic layers with distilled water (100 mL).
8. Extract eugenol from the organic phase with potassium hydroxide solution (3 M, 3x50 mL).
9. Adjust the pH of the combined alkali layers to 9 by drop-wise addition of concentrated
hydrochloric acid.
10. Extract eugenol from the milky aqueous layer with DCM (3x20 mL).
11. Dry the combined organic layers over magnesium sulphate.
12. Remove the solvent (DCM) by rotary evaporation (atm pressure; 60 ◦C bath).
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