Steam Distillation - Clove Oil
Abstract:
In this experiment, a situ method steam distillation was performed and essential oils were
isolated from cloves. Once the oils were obtained, extraction techniques were used to extract a
crude, eugenol, and acetyleugenol product sample. These samples were submitted for GC
analysis and the normalization area percents were calculated to confirm their purity; for the
crude sample it was 93.95% eugenol and 6.05% acetyleugenol, for the eugenol sample it was
100% eugenol and 0% acetyleugenol, and for the acetyleugenol sample it was 24.84% eugenol
and 75.16% acetyleugenol. The IR spectrum was also found for the eugenol and acetyleguenol
products, which confirmed their identities; the eugenol sample showed the presence of the
alcohol functional group O-H at 3425.19 cm-1 and both alkene C=C at 1604.43 cm-1 and
aromatic C=C at 1509.35 cm-1. The acetyleugenol sample showed the presence of ester C=O at
1760.27 cm-1, both alkene C=C at 1506.83 cm-1 and aromatic C=C at 1417.46 cm-1.
Introduction:
Figure11:
eugenolacetyleugenol
The primary constituents of the essential oils from cloves are the organic compounds eguenol
and acetyleugenol (structures pictured above in Figure1); these natural oils are associated with
the characteristic aroma that cloves have. The perfume industry takes advantage of these
natural cloves by using their aromatic oils in their products1. One method used to isolate clove
oil is steam distillation. This distillation technique requires liquids to be heated to their boiling
points and conducted their hot vapors into a cooling device where they condense; this process
involves steam mechanically carrying the oils through the distillation process1. Water is used as
the liquid that is boiled in the flask containing the cloves; this is because clove oils and water
are immiscible. In order to use steam distillation effectively to isolate organic compounds that
decompose near their boiling points the use of immiscible liquids is required. This distillation
technique relies on the difference in boiling points between liquids. Since these liquids cannot
homogenously mix they will boil separately from each other but at a lower temperature than
the actual boiling points of either compound; this depression in the temperature allows the
liquids to evaporate at a lower temperature avoiding decomposition of product. Each liquid
independently exerts a vapor pressure against the external pressure until the sum of their
pressures equal the external pressure and they begin to boil; the temperature at which this
occurs is the boiling point of the mixture. The apparatus used in this experiment to complete
the
steam
distillation
is
pictured
below
in
Figure
2.
Figure22:
Condenser
Condenser
WaterOut
WaterOut
WaterIn
WaterIn
BoilingFlask
BoilingFlask
Distillate
Distillate
HeatSource
HeatSource
The resulting distillate is a mixture of water and the clove oil; in order to isolate the crude oil
along with the eugenol and acetyleugenol compounds as pure products, an extraction must be
performed. Extraction is a separation technique takes advantage of the way different
compounds distribute themselves between two layers of immiscible liquids based on their
solubility; the denser layer is always the bottom layer when separated. Acid base chemistry
may also be utilized by this method to separate mixtures of acidic and/or basic compounds in
the presence of neutral materials3. Gas Chromatography (GC) is a separation technique that is
used to separate individual components of a mixture and obtain information about their
identities and concentrations. In this experiment, GC analysis was used to confirm the purity of
crude, eugenol, and acetyleugenol samples. This process exploits the difference in volatilities
between the individual components by using a GC instrument to heat a mixture4. As the
individual components vaporize separately from each other in the gaseous mobile phase they
are transported through the stationary phase; the affinity of one of these phases over the other
for each component is what results in their separation. During this process, the time and speed
at which the separate components absorb and travel through the stationary phase is monitored
and the detector’s response is charted as a function of time in a plot called a chromatogram4;
this can then be analyzed to find the actual amount of each component present. Infrared
Spectroscopy (IR) was used to confirm the identities of the eugenol and acetyleugenol
products. The products are run on a special instrument, called an IR spectrometer which
produces an IR spectrum containing information about the structures of the compounds.
During the process of IR spectroscopy, an organic molecule is exposed to infrared radiation;
when this radiant energy matches the energy of a specific molecular vibration, absorption
occurs and gives rise to bands at approximately the same frequencies5. These wavenumbers, or
frequencies, at which the molecule absorbs the radiation gives information as to the functional
groups present in the molecule and, as a result, can be identified5.
Figure
36:
Compound| Formula| Physical properties| MW (g/mol)| mass (g)| mol| mp (°C)| bp (°C)|
density (g/ml)| Water solubility (yes if ≥3%)| cloves| ---| ---| ---| 25.0903| ---| ---| ---| ---| ---|
eugenol| C10H12O2| colorless liquid| 164.2| 1.0839| | -7.5| 253.2| 1.067| no| acetyleugenol|
C12H14O3| colorless liquid| 206.2| | | 29.0 - 31.0| 281-286| 1.079| no| water| H2O| colorless
liquid| 18.02| 100.0| | 0.00| 100.0| 1.000| yes| dichloromethane| CH2Cl2| colorless liquid|
84.93| | | -97.0| 40.0| 1.326| no| 10 % sodium hydroxide sol'n| NaOH (in water)| colorless
liquid| 40.00| | | -10.0| 105.0| 1.110| yes| hydrochloric acid| HCl| colorless/pale yellow
liquid|
36.46|
---|
---|
-70.0|
110.0|
1.047|
yes|
Experimental:
To begin this experiment, a simple macro scale distillation apparatus, pictured above in Figure
2, was set up and the side arm of the boiling flask was corked. The following procedure used for
this experiment was written, compiled, and edited by Jeffery E. Elbert and Linda S. Paar.
25.0903 g of cloves were obtained and placed in the boiling flask along with 100 mL of distilled
water. The heat was turned on to induce boiling of the water then closely monitored and
turned down as needed to prevent foaming over. The heat was turned off after 54 mL of
distillate (a milky white liquid) was collected and the mantel was lowered to allow the
apparatus to cool. The distillate was transferred to a clean flask. 60 mL of distilled water was
then added to the boiling flask and the heat was turned on again until the water boiled. The
heat was turned off again after 60 mL was distilled over; this was added to the same flask as
before for total of 118 mL of distillate. The flask was corked and the apparatus was
disassembled. The distillate sat in a drawer for 2 days. The distillate was removed from drawer;
it had separated into a milky white liquid and a clear liquid. It was a mixture of water and the
clove oils and since the oil was only a minor fraction of the distillate an extraction was
performed in order to isolate the oils. The extraction sequence is provided below in Figure 4.
Figure4:
AqueousLayer
AqueousLayer
OrganicLayer
OrganicLayer
eugenol
eugenol
OrganicLayer
OrganicLayer
AqueousLayer
AqueousLayer
acetyleugenol
acetyleugenol
â…•
â…•
â…˜
â…˜
NaOH
NaOH
AqueousLayer
AqueousLayer
OrganicLayer
OrganicLayer
Crude
Crude
Distillate
Distillate
CH2Cl2
CH2Cl2
Evaporate
Evaporate
*discard
*discard
Evaporate
Evaporate
CH2Cl2
CH2Cl2
HCl
HCl
Evaporate
Evaporate
*discard
*discard
First the distillate was transferred to a 250 mL separatory funnel but the stopcock wasn’t closed
so it resulted in a slight loss of distillate. 15 mL of dichloromethane was then added to the
funnel and the funnel was corked. After the solution of dichloromethane and distillate was
mixed by inverting the funnel and venting every so often to relieve pressure it was let sit so that
the immiscible aqueous and organic layers could separate. The organic compounds from the
clove oils are insoluble in water so they dissolved into the lower organic dichloromethane layer.
The organic layer (a clear liquid) was then drained into flask A. This same process of adding 15
mL of dichloromethane, mixing, and allowing layers to separate was repeated two more times;
the organic layers were all added to flask A. The left over upper aqueous layer (a milky white
liquid) was discarded. 3.9163 g of calcium chloride pellets were added to flask A and mixed until
clumping was no longer observed. The solution from flask A was then decanted into a clean
flask leaving the pellets behind; 38 mL of solution was present. 7.6 mL of the solution was
transferred to a new vial. A boiling stick was added to the vial and it was placed on a steam
bath. After the dichloromethane solution had evaporated the crude product remained and the
vial was submitted for GC analysis; results shown below in Figure 4.
Figure4:
Next, the remaining 30.4 mL of the organic dichloromethane layer from flask A was transferred
back into the separatory funnel. Acid base chemistry was then used to isolate pure eugenol and
acetyleugenol compounds. 10 mL of 10% NaOH was added to the funnel and the solution mixed
by inverting the funnel and releasing pressure every so often. The funnel was let sit while the
aqueous and organic layers separated. The bottom organic layer (a milky white liquid) was
drained into a holding flask and the upper aqueous layer (a milky yellow liquid) was drained
into a new flask B. The organic layer was then transferred back into the separatory funnel and
this process was repeated two more times adding all the aqueous layers into flask B. The
chemical reaction that occurred when the organic dichloromethane layer was extracted with
NaOH, shown below in figure 4, resulted in eugenol being dissolved into the aqueous layer and
acetyleugenol
being
dissolved
into
the
organic
layer.
Figure5:
The remaining organic layer (a milky white liquid) was added to a new flask C and dried with
3.5404 g of calcium chloride pellets; this 23.5 mL of dried organic layer was then decanted into
a clean vial. A boiling stick was added to the vial and it was placed on a steam bath to evaporate
the solvent. This vial containing the acetyleugenol product was also submitted for GC and IR
analysis; provided below, Figure 6 shows the GC results and Figure 7 shows the IR results.
Figure6:
Figure7:
Acid base chemistry was then utilized again in order to extract a pure eugenol compound from
the aqueous layer in flask B. 200 drops of HCl was added to flask B in order to acidify the
aqueous layer until it reached a pH of 1 (a pink color) on litmus paper. When the HCl was added
a white precipitate formed and once a pH of 1 was reached the oil separated from the water
and resulted in a milky white liquid. The liquid was then transferred back into the separatory
funnel and 8 mL of dichloromethane was added to it. The funnel was inverted and vented every
so often to release pressure. After the aqueous and organic layers separated, the lower organic
layer (a milky light yellow liquid) was drained into a new flask D. This process of adding 8 mL of
dichloromethane, inverting, and letting the layers separate was repeated two more times; the
organic layers were all added to flask D. The remaining aqueous layer was discarded. 3.9916 g
of calcium chloride pellets were then added to flask D to dry the organic layer. After no more
clumping was observed 23.5 mL of solution was decanted into a vial leaving the pellets behind.
A boiling stick was added to the vial and it was placed on a steam bath. The solution evaporated
and the remaining 1.0839 g of eugenol product was submitted for GC and IR analysis; provided
below, Figure 8 shows the GC results and Figure 9 shows the IR results.
Figure8:
Figure9:
Calculations:
Normalizationcrudesample
Area
%
eugenol→1743120.901743120.90
acetyleugenol→112245.021743120.90
Normalization
Area
Area
Normalization
Area
Area
–
%
%
%
%
+
112245.02×100=93.95%
Area
%
+
112245.02×100=6.05%
eugenol
sample
eugenol→1248421.85248421.85+0×100=100%
acetyleugenol→0248421.85+0×100=0%
–
acetyleugenol
eugenol→10623.5110623.51+32148.95×100=24.84%
acetyleugenol→32148.9510623.51+32148.95×100=75.16%
Results
and
Discussion:
The GC results were analyzed and the normalization area percent for eugenol and
acetyleugenol were calculated for each sample submitted. The crude sample resulted in 93.95%
eugenol and 6.05% acetyleugenol. The eugenol sample was 100% eugenol and 0%
acetyleugenol; these results follow the expected that no other compounds would be present.
The acetyleugenol sample didn’t match the expected as well as the eugenol by resulting in
24.84% eugenol and 75.16% acetyleugenol; these results do follow the expected somewhat
though by acetyleugenol having the higher percent. The IR spectrum results for the eugenol
sample submitted showed the presence of the alcohol functional group O-H at 3425.19 cm-1. In
this case, the O-H presence is characteristic to eugenol since it is not present in the
acetyleugenol compound. Both alkene C=C at 1604.43 cm-1 and aromatic C=C at 1509.35 cm-1.
These results are consistent with the expected presence of O-H between 3200 – 3650 cm-1,
alkene C=C between 1600 – 1680 cm-1 and also aromatic C=C around 1430-1500 cm-1.7 The
identity of acetyleugenol was also confirmed with the IR spectrum results by showing the
presence of ester C=O at 1760.27 cm-1. In the case of acetyleugenol, the presence of the ester
functional group is what characterizes it from eugenol. Both alkene C=C at 1506.83 cm-1 and
aromatic C=C at 1417.46 cm-1. These results match the expected presence of ester C=O
between 1650 – 1780 cm-1, alkene C=C between 1600 – 1680 cm-1 and also aromatic C=C
around
1430-1500
cm-1.7
Conclusions:
In conclusion, the GC results showed that a pure eugenol and mostly pure acetyleugenol
samples were able to be extracted. This small amount of eugenol in the acetyleugenol sample
might be due to an error when separating the organic and aqueous layers; some of the aqueous
layer containing the eugenol compound might have been left in the organic layer containing the
acetyleugenol. Also, the IR spectrum results were consistent with the expected, confirming the
identities
of
the
eugenol
and
acetyleugenol
products.
References:
(1) Williamson. "Chapter 6." Macroscale and Microscale Organic Experiments. 4 ed.
Boston/New York: Houghton Mifflin, 2003. 2-3. Print. “Steam distillation lab handout”. Written,
compiled, and edited by Jeffrey E. Elbert and Linda S. Paar, Department of Chemistry, University
of
Northern
Iowa
(2) "Recovery of Citral from lemon grass oil by steam distillation." Pharmaceutical Information,
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and
Blogs
:
Pharmainfo.net.
N.p.,
n.d.
Web.
1
May
2013.
<http://www.pharmainfo.net/reviews/recovery-citral-lemon-grass-oil-steam-distillation>.
(3) “Extraction lab handout”. Written, compiled, and edited by Jeffrey E. Elbert and Linda S.
Paar,
Department
of
Chemistry,
University
of
Northern
Iowa
(4) "Gas Chromatography." Chromatography - Everything about Chromatography and Analytical
Chemistry.
N.p.,
n.d.
Web.
1
May
2013.
<http://www.justchromatography.com/chromatography/gc>.
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<http://orgchem.colorado.edu/Spectroscopy/irtutor/tutorial.html>.
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N.p.,
n.d.
Web.
3
May
2013.
<http://sciencelab.com>.
(7) "IR Chart." Organic Chemistry at CU Boulder. N.p., n.d. Web. 2 May 2013.
<http://orgchem.colorado.edu/Spectroscopy/specttutor/irchart.html>.