Isolation of Eugenol
Colby College – Organic Chemistry 241 Lab
12/7/2010
This lab explored techniques in steam-distillation to extract clove oil from ground cloves.
In the second part of the experiment, designed by the students, eugenol was isolated from clove
oil via chemically active extraction, using acid-base chemistry. This isolated compound was
analyzed via Infrared Spectroscopy and Gas Chromatography.
Eugenol, eugenol acetate and caryophyllene (Figure 1) were isolated from ground cloves
via steam distillation. To do this, 5.04g of ground cloves were added to a 500mL round bottom
flask with 40mL of dH2O, boiling stones and 3 drops of an antifoaming agent (to prevent violent
boiling). The contents of the flask were heated using a heating mantle for 75 minutes. The
distillate was condensed through a water jacket and allowed to collect in a graduated cylinder.
Steam distillation allowed the clove oil to co-distill with the water, which occurs at a lower
temperature than the boiling temperature of the individual solutions. This was desirable, because
high temperatures can decompose the components of clove oils. 35mL of distillate were
transferred to an Erlenmeyer flask, 2g of NaCl were added, and the solution was cooled in ice
water. NaCl dissolves in H2O, and shifts the equilibrium, driving the organic compounds into the
organic layer. The solution was transferred to a 125mL seperatory funnel, and 50mL of hexane
were added, and the funnel was shaken with venting to extract the organic clove oils from the
aqueous layer. The aqueous layer was drained and discarded, and the organic layer was drained
into a clean Erlenmeyer flask. The organic layer was then dried with solid sodium sulfate, and
was gravity filtered into a round bottom flask. The oils were isolated from the hexane solvent via
rotary evaporation, and transferred to a clean glass vial and stored for further analysis.
In the second part of this lab, eugenol was isolated from the clove oil obtained in the first
part of the lab. To accomplish this, a series of chemical extractions were performed. First, 15mL
of hexane were added to the clove oil (in the vial, to ensure that all oil was obtained), creating a
large volume organic layer, and this solution was transferred to a 125mL seperatory funnel. Then
25mL of 5% NaOH was added to the funnel, and the funnel was shaken with venting. This
yielded an aqueous layer and an organic layer. The aqueous layer contained the eugenol, while
the eugenol acetate and caryophellene remained in the organic layer. Eugenol is weakly acidic
because it is a phenolic compound, whereas eugenol acetate and caryophellene are neutral
compounds. The addition of NaOH allows for a chemically active extraction, which allows for
the selective formation of the eugenol salt, but not a reaction with the neutral compounds. The
eugenol will react with the NaOH, resulting in the formation of a sodium salt of eugenol that is
soluble in the aqueous layer. The neutral compounds do not react with NaOH, and remain in the
organic layer. The aqueous layer was then drained, and set aside. The remaining organic layer
was washed again with 25mL of 5% NaOH to ensure complete extraction of eugenol, and the
aqueous layer was drained and added to the first aqueous layer. The organic layer was discarded.
The aqueous layer was cooled on ice (to prevent dangerous levels of heat evolution when the
acid was added), and 50mL of 6M HCl were added to the solution, ensuring that the solution was
acidic (confirmed with litmus paper test strips). This step ensures that the sodium salt of eugenol
is protonated, displacing the sodium ion, yielding the desired eugenol.
This solution was transferred to a 125mL seperatory funnel with 15mL of hexane. This
funnel was shaken with venting, which ensured that the organic eugenol entered the organic
layer (hexane) in the mixture. The organic layer was drained and set aside, and then 15mL of
hexane were added to the remaining aqueous layer, and the extraction was repeated to ensure the
complete extraction of eugenol. This organic layer was drained into the first organic layer. The
organic solution was dried with anhydrous sodium sulfate, and this mixture was filtered by
gravity filtration to yield a water-free organic solution in a 150mL round bottom flask. This
hexane solvent was evaporated via rotary evaporation, leaving the eugenol oil behind in the
flask. A sample of this oil was prepared in dichloromethane so that it could be analyzed by gas
chromatography, and the rest of the oil was saved for IR analysis.
The gas chromatograph (Graph 1) shows that the sample is almost 100% eugenol, with
trace contamination of caryophellene, confirming efficient methods of separation and extraction.
This trace impurity could be due to residue left in the glassware that was not washed away after
the extractions.
A sample of the eugenol oil was analyzed by infrared spectroscopy (IR). The spectrum
(Graph 2) identifies functional groups present in the molecules in the solution. The presence (or
absence) of these functional groups allows for the identification of molecules present. Spectral
data below 1600 cm-1 is considered molecular fingerprint, and for the purposes of this lab, is not
analyzed. The two peaks at 1611.81 cm-1 and 1637.77 cm-1 represent carbon-carbon double
bonds that were expected in all of the isolated alkenes. No peak is observed in the 1750 cm-1 to
1735 cm-1 range, which shows that the acetate ion is not present, because no C=O is observed, so
no eugenol acetate in present as confirmed by the IR. The peaks at 2938.28 cm-1 and 2842.62 cm1
represent the C-H bond in the alkanes found in all three molecules, and the peak at 3003.67 cm1
represents the C-H bond in the alkenes found in all three molecules. These three peaks are not
diagnostic of any one molecule, but are expected. A peak was observed between 3580 cm-1 and
3650 cm-1 (representing an –OH functional group), this peak was observed at 3511.36 cm-1. This
peak confirms the presence of eugenol because only eugenol contains an –OH functional group.
The IR spectrum compares closely with a reference spectrum for Eugenol, further confirming
that the IR spectrum shows the presence of Eugenol.
In this lab, clove oil was isolated from ground cloves via steam distillation, which works
by allowing the clove oil to co-distill with water. Using a chemically active extraction, and rotary
evaporation, eugenol was isolated from this clove oil. Techniques in IR spectroscopy were used
to confirm the presence of eugenol, and Gas Chromatography showed that the extraction
methods were highly effective in isolating eugenol.
References:
Dalton, D.; Yip, M. Organic Chemistry in the Laboratory; D. Van Nostrand Company: New
York, 1979; pp. 26-30, 137-142
Eugenol - Infra Red Spectrum. http://www.chem.bham.ac.uk/schools/eugenolir.htm (accessed
Dec. 7, 2010).
Jones and Fleming. Organic Chemistry: 4th Edition. W.W. Norton & Company, Inc: New York,
2010; pp. 710-711
Figure 1: Structural Formulas – Eugenol, Eugenol Acetate and Caryophyllene