The experiment involved using steam distillation to extract essential oils from cloves. These oils are primarily composed of eugenol and acetyleugenol. Different techniques were used to obtain crude, eugenol, and acetyleugenol samples. GC analysis was performed on these samples to determine their purity. The results showed that the crude sample contained 93.95% eugenol and 6.5% acetyleugenol, the eugenol sample contained 100% eugenol and no acetyleugenol, and the acetyleugenol sample contained 24.84% eugenol and 75.16% acetyleugenol. IR spectra were also obtained for the eugenolsample which revealed the presence of O-H (alcohol functional group) at3425.19 cm-1,C=C(alkene)at1604.43 cm-1,and C=C(aromatic)at1509.35cm-1.Theacetyleug enolsample showedthe presenceofC=O(ester)at1760 .7 cm -1 ,C = C (alkene ) a t1506 .83 cm -1 ,and C = C (aromatic )a t1417 .46cm -1
Introduction: Figure11:eugeno lacet yleu gen olTheessentialoilsfromcloves,w hicharecomposedprimarilyofeugeno landacet yleu gen ol(picturedaboveinFigurel),giveclove st heircharacteristic aroma.Thesenaturaloilsareoftenusedinthep erfumeindustry.Steamdistillationisacommonly usedmethodforisolatingclo veoil.
The distillation technique described in this paragraph involves heating liquids to their boiling points and then collecting their hot vapors in a cooling device to condense them. Steam is used to carry the oils through the distillation process. Immiscible liquids, such as water and clove oils, are used because water is boiled in the flask containing the cloves. Immiscible liquids are necessary when isolating organic compounds that decompose near their boiling points. The technique takes advantage of the difference in boiling points between the liquids.
Since these liquids cannot mix together evenly, they will each boil separately from one another. However, they will boil at a lower temperature than their individual boiling points. This decrease in temperature prevents the liquids from decomposing. Each liquid exerts its own vapor pressure against the external pressure until the total pressure equals the external pressure, causing them to boil. This temperature is known as the boiling point of the mixture. Figure 2 below shows the apparatus used in this experiment for steam distillation.
Figure 22 shows the setup for distillation. The condenser receives water in and water out, while the boiling flask contains the mixture. Heat source is required to initiate the distillation process. The resulting distillate is a mixture of water and clove oil. To obtain pure products like crude oil and eugenol and acetyleugenol compounds, extraction must be done. Extraction involves using immiscible liquids to separate compounds based on their solubility. The denser layer is always the bottom layer when separated.
Acid base chemistry can also be used to separate mixtures of acidic and/or basic compounds in the presence of neutral materials3. Gas Chromatography (GC) is a separation technique that is employed to separate individual components of a mixture and gather information about both their identities and concentrations. In this experiment, GC analysis was utilized to verify the purity of crude, eugenol, and acetyleugenol samples. This procedure takes advantage of the varying volatilities of the individual components by utilizing a GC instrument to heat a mixture4.
In chromatography, the individual components in the gaseous mobile phase are vaporized separately and transported through the stationary phase. The separation of these components is based on the affinity of one phase over the other. Throughout this process, the absorption and travel time of each component through the stationary phase is monitored. The detector’s response is recorded as a chromatogram, which can be analyzed to determine the quantity of each component present.
Using Infrared Spectroscopy (IR), the identities of the eugenol and acetyleugenol products were confirmed. The products are analyzed using an IR spectrometer, a specialized instrument that generates an IR spectrum with valuable information regarding compound structures. In the process of IR spectroscopy, an organic molecule is subjected to infrared radiation. Absorption takes place when the energy of the radiation corresponds to a specific molecular vibration, resulting in bands appearing at similar frequencies.
The absorption of radiation by a molecule at certain wavenumbers or frequencies can provide information about the functional groups present in the molecule, allowing for identification.
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. 2| 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 start the experiment, a simple macro scale distillation apparatus as shown in Figure 2 was set up with the side arm of the boiling flask being corked. The following procedure for this experiment was written, compiled, and edited by Jeffery E.
Elbert and Linda S. Paar collected 0903 g of cloves and mixed them with 100 mL of distilled water in a boiling flask. The water was heated until it boiled, ensuring that the heat was controlled to prevent foaming over. Once they obtained 54 mL of distillate, which had a milky white appearance, they turned off the heat source and let the apparatus cool down. They then transferred the resulting distillate to a clean flask. Afterward, an additional 60 mL of distilled water was added to the boiling flask, and the heat source was once again activated, causing the water to boil.
The heat was turned off once again after distilling 60 mL. This 60 mL was then added to the same flask as before, resulting in a total of 118 mL of distillate. The flask was corked and the apparatus was disassembled. The distillate sat in a drawer for 2 days and upon removal, it had separated into a milky white liquid and a clear liquid. This mixture consisted of water and clove oils, with the oil being only a small proportion of the distillate. To isolate the oils, an extraction was performed. Please refer to Figure 4 for the provided extraction sequence. Figure 4 shows the aqueous layer.
The distillate was initially transferred to a 250 mL separatory funnel, but the stopcock was not properly closed, resulting in a slight loss of distillate. Afterwards, 15 mL of dichloromethane was added to the funnel and it was corked.
The solution of dichloromethane and distillate was combined by inverting the funnel and venting periodically to release pressure. Subsequently, it was left undisturbed for the immiscible aqueous and organic layers to separate. The organic compounds from the clove oils, which do not dissolve in water, dissolved into the lower organic dichloromethane layer. The resulting transparent liquid, known as the organic layer, was then transferred into flask A. This process of adding 15 mL of dichloromethane, mixing, and waiting for the layers to separate was repeated two more times, gathering all the organic layers in flask A.
The milky white liquid, the leftover upper aqueous layer, was disposed of. Calcium chloride pellets weighing 3.9163 g were introduced to flask A and mixed until clumping stopped. The resulting solution from flask A was then poured into a clean flask, leaving the pellets behind; there was a total of 38 mL of solution. From this solution, 7.6 mL was transferred to a new vial with a boiling stick added before placing it on a steam bath. After evaporation of the dichloromethane solution, the crude product remained in the vial and was submitted for GC analysis (see Figure 4 for results).
Figure 4 demonstrates the process of transferring the organic dichloromethane layer (30.4 mL) from flask A back into the separatory funnel. This step aimed to separate pure eugenol and acetyleugenol compounds using acid-base chemistry. To achieve this, a solution of 10 mL of 10% NaOH was added to the separatory funnel and mixed by periodically inverting the funnel and releasing pressure. After allowing time for the aqueous and organic layers to separate, the milky white bottom organic layer was drained into a holding flask, while the milky yellow upper aqueous layer was drained into a new flask B. This procedure was repeated twice, with each iteration involving transferring the organic layer back into the separatory funnel and adding all collected aqueous layers into flask B. As a result of reacting with NaOH, eugenol dissolved in the aqueous layer while acetyleugenol dissolved in the organic layer.
Moving on to Figure 5, it can be observed that the remaining milky white organic layer from before was transferred to a new flask C. It was then dried using calcium chloride pellets weighing 3.404 g.The resulting dried organic layer measured 23.5 mL and was decanted into a clean vial along with a boiling stick.The vial containing acetyleugenol product underwent evaporation on a steam bath in order to completely remove solvent contentFinally, the vial containing acetyleugenol product was sent for GC and IR analysis for further examination and characterization. The results, shown in Figure 6 (GC) and Figure 7 (IR), demonstrate the use of acid-base chemistry to isolate a pure eugenol compound from flask B’s aqueous layer. To achieve this, 00 drops of HCl were added to flask B, causing the aqueous layer to become acidic with a pH of 1 as indicated by pink litmus paper. This addition resulted in the formation of a white precipitate and separation of oil from water, resulting in a milky white liquid. This liquid was then transferred back into the separatory funnel along with 8 mL of dichloromethane. The funnel was intermittently inverted and vented to release pressure. After separating the aqueous and organic layers, the lower organic layer with its milky light yellow appearance was poured into a new flask D.
The process involved adding 8 mL of dichloromethane to flask D, inverting it, and allowing the layers to separate. This step was repeated twice more, and all of the organic layers were added to flask D. The remaining aqueous layer was discarded. Then, 3.9916 g of calcium chloride pellets were added to flask D to dry the organic layer. Once clumping was no longer observed, 23.5 mL of solution was transferred to a vial, while leaving the pellets behind. A boiling stick was added to the vial, which was then placed on a steam bath. The solution evaporated, resulting in 1.839 g of eugenol product for GC and IR analysis. The GC results are shown in Figure 8, and the IR results are shown in Figure 9.
The normalization area percentages for eugenol and acetyleugenol were calculated for each submitted sample. The crude sample had 93.95% eugenol and 6.05% acetyleugenol. The eugenol sample had 100% eugenol and 0% acetyleugenol, which was the expected result with no other compounds present.The sample of acetyleugenol did not match the expected results, yielding 24.84% eugenol and 75.6% acetyleugenol. However, these results still somewhat align with expectations as acetyleugenol had a higher percentage. The infrared (IR) spectrum analysis of the eugenol sample revealed the presence of the alcohol functional group O-H at 3425.19 cm-1, which is characteristic of eugenol and absent in acetyleugenol. The spectrum also showed the presence of alkene C=C at 1604.43 cm-1 and aromatic C=C at 1509.35 cm-1, which align with the expected presence of O-H between 3200 – 3650 cm-1, alkene C=C between 1600 – 1680 cm-1, and aromatic C=C around 1430-1500 cm-1. The identity of acetyleugenol was confirmed by the presence of ester C=O at 1760.27 cm-1 in its IR spectrum. In contrast to eugenol, acetyleugenol is characterized by the ester functional group. The spectrum also showed alkene C=C at 1506.83 cm-1 and aromatic C=C at 1417.46 cm-1, matching the expected presence of ester C=O between 1650 – 1780 cm-1, alkene C=C between 1600 – 1680 cm-1, and aromatic C=C around 1430-1500 cm-1. In conclusion, the GC analysis confirmed the extraction of a pure eugenol sample and mostly pure acetyleugenol sample.
The small amount of eugenol in the acetyleugenol sample may be due to a mistake in separating the organic and aqueous layers. It is possible that some of the aqueous layer, which contains eugenol, was not fully separated and remained in the organic layer with acetyleugenol.
Furthermore, the IR spectrum results confirmed the expected identities of both 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 from the Department of Chemistry at the University of Northern Iowa conducted a study on the recovery of citral from lemon grass oil using steam distillation. The study is available on the website Pharmainfo.net and provides detailed information on the process.
The Department of Chemistry at the University of Northern Iowa has also written an extraction lab handout, which further explains the process.
Furthermore, the website Chromatography.net offers information about gas chromatography, a common technique used in analytical chemistry.
The following are web links with their corresponding dates and titles:
– “http://www.justchromatography.com/chromatography/gc” – N. p., n. d. Web. 1 May 2013.
– “http://orgchem.colorado.edu/Spectroscopy/irtutor/tutorial.html” – N. p., n. d. Web. 3 May 2013.
– “http://sciencelab.com” – N. p., n. d. Web. 3 May 2013.
– “http://orgchem.colorado.edu/Spectroscopy/specttutor/irchart.html” – N. p., n. d. Web. 2 May 2013.
