Isolation of R-(+)-Limonene from Orange PeelGabrillo. Shaira L. BS-Chemistry, University of San Carlos – Talamban Campus Abstract R-(+)-Limonene is a common naturally occurring compound with a citrus scent. It is usually used for fragrance, and is commonly found in the peelings of citrus fruits. Steam distillation was deployed to see its effectiveness in separating immiscible mixtures. The natural oils of orange peels were extracted to isolate the limonene through steam distillation. The peel of oranges is boiled in water and the oil produced distilled in steam at a temperature just below 100 °C, well below its normal boiling point. The immiscible oil was then separated, after which the presence of limonene from the obtained oil was checked using the Baeyer’s test. I. Introduction Limonene (1-methyl-4-prop-1-en-2yl-cyclohexene) is an unsaturated hydrocarbon, classed as a terpene. At room temperature it is a colourless oily liquid with the smell of oranges. Its molecular formula is C10H16 and its boiling point is 176 °C. Limonene is a chiral molecule with two optical isomers (enantiomers). The major biological form d-limonene, the (R)enantiomer, is used in food manufacture and medicines. It is also used as a fragrance in cleaning products, a botanical insecticide, and due to its flammability, a potential biofuel. The (S)-enantiomer, llimonene, is also used as a fragrance but has a piney, turpentine odour [1]. D-limonene is often used as an additive in food products and fragrances, and is classified by the U.S. Food and Drug Administration (FDA) as Generally Recognized as Safe (GRAS) [2]. Extraction of d-limonene can be done by simple steam distillation, a technique for the isolation of many waterinsoluble compounds that are unstable at temperatures near their boiling points [3]. This experiment measures the effectiveness of steam distillation in separating limonene from its natural origin. The said method for the extraction and quantification of limonene from orange peels is discussed further in this article. II. Materials and methods This experiment was performed in the organic laboratory of the University of San Carlos – Talamban Campus. Pithless orange peelings were blended and distilled using steam distillation. The oil obtained was then extracted and dried to obtain pure limonene. Baeyer’s test was conducted to confirm presence of limonene in the extract. II.A. Preparation of sample Orange peelings were obtained from five fresh oranges. The pith was scraped off the peelings before proceeding. The pithless peelings were then shredded into small pieces and blended in an industrial grade blender. 150-mL of water was added until the blended mixture was smooth. The contents were then transferred into a 500mL round-bottom flask. 50-mL of water was used to rinse the mixture left in the blender. The rinsed mixture was added into the 500-mL round-bottom flask. Boiling chips and a pinch of NaCl was added to the mixture in the flask before distillation. II.B. Steam distillation The set-up was prepared for steam distillation as shown in figure 1. The distilling flask was filled to 2/3 of its capacity with water. Apart from the pressure tube, another opening connects the distilling flask to the round-bottom flask containing the blended orange peels. The round-bottom flask was connected to the condenser where the extracted oil would pass through towards the receiving flask. To the resulting solution. no change is initially observed. color of solution changed from red-orange to a yellowish tint. When it is mixed with an alkene or alkyne. The alkenes are then readily oxidized by potassium permanganate. Baeyer’s test. and bromine test were performed to confirm the presence of limonene in the obtained filtrate. confirming the presence of an alkene. upon addition of bromine reagent to the dried limonene. otherwise no reactions will occur. In a separate vial. The extracted oil was then transferred to a vial containing anhydrous calcium chloride to dry the limonene. five drops of 0. II. the color of Br2 rapidly disappears. Baeyer’s Test In a vial. and brown precipitate was found at the bottom of the vial confirming the presence of an alkene. VI. being an alkene. the disappearance of the purple color of potassium permanganate and the appearance of brown precipitate (MnO2) shows a positive test result. Boiling chips were added in the round-bottom flask along with the orange peelings to ensue uniform heating throughout the mixture. Bromine test and permanganate test are used to detect presence of alkenes and alkynes. after which the vial was shaken thoroughly. or the upper layer of the filtrate.1M NaOH was mixed with five drops of KMnO4. Baeyer’s test Occurring reaction during After Baeyer’s test. Reaction between the reagent and limonene in bromine test is shown in equation 1 below: Equation 1. 150-mL of water was used in blending the peelings. Addition of table salt was performed on the same flask to minimize emulsion during extraction by making the organic layer less soluble in water. the anhydrous salt absorbs the water adhered on the extracted oil making CaCl 2 hydrated and leaving behind dried limonene. no more than 50% of the container used should be filled with the material to be distilled for it will cause the formation of a jam which is hard to remove. III. while the alkanes in this situation do not react with potassium permanganate. two to three drops of the dried limonene was dissolved in 0. NaOH was added to alkalize KMnO4. five drops of the dried limonene was added. Limonene. which in this case was limonene. Steam distillation setup From the filtrate. Occurring reaction during bromine test In the Baeyer’s test. the oils or the upper layer of the immiscible mixture was removed using a micropipette. produced positive results in both tests. The extracted oil. or permanganate test. In this case. In the bromine test. color of dried limonene solution changed from purple to colorless. Reaction is shown below in equation 2: Equation 2. Conclusion . Pith was scraped off from the orange peels before blending to prevent volatile limonene from escaping.C. was exposed to anhydrous calcium chloride to desiccate the oil. the solutions of bromine in CHCl3 have an intense red-orange color. One to two drops of bromine test reagent was then added to the prepared solution of limonene and DCM.Figure 1. Results and Discussions Limonene is a volatile organic compound. When Br2 in CHCl3 is mixed with an alkane.5-mL of dichloromethane. This technique is used for separating substances which are immiscible with water.pdf [3] Steam Distillation: Isolation of Limonene from Orange Peels. If the substances to be distilled are very sensitive to heat. 1994. Direct extraction by heating would result in decomposition whereas steam distillation does not destroy the chemicals involved. Retrieved from http://www. including some that are solids at normal temperatures.K.epa. E. R. however. Thompson A. volatile in steam & having high vapour pressure at the boiling temperature of water [5]. This process effectively allows for distillation at lower temperatures.mercyhurst.co. Disadvantages of steam distillation are that the process takes up to several hours and with little yield. reducing the deterioration of the desired products.pdf [4] Field Distillation for Herbaceous Oils. if allowed to pass through a cooling system. Retrieved from http://plato. Essential oils contain substances with boiling points up to 200°C or higher. gov/oppsrrd1/REDs/factsheets/3083fact. The fundamental nature of steam distillation is that it enables a compound or mixture of compounds to be distilled (and subsequently recovered) at a temperature substantially below that of the boiling point(s) of the individual constituent(s). Tasmania.F. condense to form a liquid in which the oil and water comprise two distinct layers. References [1] Extracting limonene from oranges by steam distillation.E. Facts. http://en. http://amrita. Supporting Information Most essential oils are obtained from the plant material by a process known as steam distillation [4]. and it has high cost. albeit to a certain degree only. The mixture of hot vapours will. these substances are volatilized at a temperature close to 100°C at atmospheric pressure.Steam distillation is an effective way of extracting limonene from orange peels..org/learnchemistry/content/filerepository/CMP/00/000/770/cf ns%20experiment%2011%20-%20extracting %20limonene%20from%20oranges%20by%20steam %20distillation. steam distillation may be applied under reduced pressure. In the presence of steam or boiling water. USA EPA: [2] http://www.1991 [5] Purification by Steam distillation/crystallisation. especially heatsensitive components. Limitations as to the effectiveness of steam distillations are also present. 2009.in/? sub=2&brch=191&sim=1547&cnt=1 [6] Steam distillation.pdf Limonene.D. Most (but not all) essential oils are lighter than water and form the top layer. The steam that is used for the distillation is generated either within the vessel that contains the plant material (by boiling water contained at the base) or by an external boiler [4]. thereby reducing the operating temperature further [6]. Citano KJ. Lilydale.edu/chemistry/kjircitano/orgla bs/orgilabexp2.vlab.org/wiki/Steam_distillat ion . Denny. VIII. It is a safe way to separate components of immiscible mixtures. VI.wikipedia.rsc.
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