*Adri, Kiersten Jayne R., Aguinaldo, Samuel Jr.
Department of Chemistry, College of Science
University of Santo Tomas, España, Manila 1008
Abstract. In this experiment, the primary objective was to isolate eugenol from cloves. An amount of 30 grams of dried cloves and 300 mL of water was distilled over a flame for over 2 hours. The distillate underwent extraction with dichloromethane, water and sodium hydroxide. Concentrated hydrochloric acid was added to the aqueous extract to lower it to pH 9; it was again extracted with 2 x 30 mL of DCM. These organic extracts were dried over anhydrous magnesium sulfate, filtered into a pre-weighed flask and had their …show more content…
Since eugenol is not soluble in water, the concentration of the eugenol in the vapor over the boiling eugenol–water suspension does not depend on concentration of the eugenol. The relative amounts of eugenol and water in the vapor simply depend on the vapor pressures of the pure materials. The vapor pressure of water at 100 °C is 760 torr, and the vapor pressure of eugenol at 100 °C is approximately 4 torr; therefore, the vapor is roughly 0.5 % eugenol. The suspension boiled when its vapor pressure was equal to the external pressure. Since both the eugenol and the water contributed to the vapor pressure of the suspension, the suspension boiled before either pure substance would normally boil. Since many essential oils contain liquids that may not survive heating at higher temperatures, steam distillation is an especially advantageous technique for isolating them because their immiscible mixture with water boils below 100 …show more content…
After obtaining the oil of cloves by steam distillation, the eugenol was isolated by extraction. In this process the fact that eugenol, because it is a phenolic compound, is weakly acidic whereas both eugenol acetate and caryophllene are neutral was considered. Thus, when the clove oil was treated with a sodium hydroxide (a strong base) it resulted in the selective formation of the sodium salt of eugenol which was soluble in the aqueous phase. The other neutral compounds did not react with sodium hydroxide and therefore remained in the organic phase. After the separation of the aqueous phase, its extraction with DCM and its acidification, the organic extract was dried over anhydrous magnesium sulfate. The eugenol was finally isolated by evaporation of the organic solvent in the rotary