Steam Distillation – Clove Oil
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.
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.
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...
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