STEAM DISTILLATION OF ORANGE OIL

Transcription

1 Chem 306 Section (Circle) M Tu W Th Name Partners Date STEAM DISTILLATION OF ORANGE OIL Materials: 3 oranges, boiling chips, NaCl, ice, blender, grater, 50 ml buret, distillation apparatus, screw-top vial, ice, stirring rod, rinse bottle, vacuum grease, aluminum foil, cleaning brushes, detergent (Dawn) Purpose: In this laboratory activity you will separate orange oil from orange peel by the technique of steam distillation. Introduction: In this experiment we will be extracting D limonene (4-Isopropeny-1- methyl-cyclohexene) from orange peel by use of steam distillation. Limonene belongs to a class of compounds called terpenes. Terpenes are a large and varied class of hydrocarbons, produced primarily by a wide variety of plants, particularly conifers. They are the major components of resin, and of turpentine produced from resin. The name "terpene" is derived from the word "turpentine". When terpenes are modified chemically, such as by oxidation or rearrangement of the carbon skeleton, the resulting compounds are generally referred to as terpenoids. Terpenes and terpenoids are the primary constituents of the essential oils of many types of plants and flowers. Essential oils are used widely as natural flavor additives for food, as fragrances in perfumery, in aromatherapy, and in traditional and alternative medicines. Synthetic variations and derivatives of natural terpenes and terpenoids also greatly expand the variety of aromas used in perfumery and flavors used in food additives. The building block of all terpenes is an isoprene unit. A limonene molecule contains two isoprene units. or Isoprene Units The terpene D-limonene is the major chemical component in orange oil and has a variety of uses. As the main odor constitutent of the citrus family, D limonene can be used as an additive to impart an orange-like fragrance or flavor to foods, toiletries, and cleaning products. Pure limonene is used as a solvent to replace other solvents such as toluene, mineral spirits, turpentine, acetone, etc. Flea and tick shampoos also 1

2 contain D-limonene as do some insecticides. Limonene is an irritant to the skin and eyes. D limonene L limonene There are two isomers (same chemical formula but different structure) of limonene, D and L limonene. A quick glance at the structural representations of limonene above reveals that both of these isomers have the same connection of atoms. How can they be isomers? D and L limonene are stereoisomers, specifically, enantiomers or optical isomers. Stereoisomers are structures that differ only in the spatial arrangement of atoms. Enantiomers, such as D and L limonene, are non-superimposable mirror images of each other (as you will see later on in the lab). Two compounds that are enantiomers of each other have the same physical properties, except for the direction in which they rotate polarized light and how they interact with different enantiomers of other compounds. In nature, only one enantiomer of most biological compounds, such as amino acids (L), is present. As a result, different enantiomers of a compound may have substantially different biological effects. In the structures above, the wedge line in the D isomer represents a bond projecting out of the plane of the paper. The dashed line in the L limonene structure represents a bond projecting behind the plane of the paper. Distillation is a method used to separate substances based on differences in their boiling temperatures (volatilities). Steam distillation is a special case of the distillation of an aqueous mixture. A mixture of water and an organic material is boiled in a distillation apparatus causing vaporized water (steam) and organic liquid to distill into a receiver. Steam distillation allows the separation of this organic liquid from its parent plant material at a temperature well below its boiling point so that there is little chance of decomposition. Many essential oils are separated from plant materials by steam distillation. Some essential oils have components that are too fragile even for steam distillation. Other methods of recovering essential oils include cold pressing and chemical extraction. Safety: Be sure that your distillation apparatus is secure before beginning the distillation. Have your instructor check your set-up before you begin. Limonene is a skin and eye irritant. 2

3 Procedure: 1. Peel three or four medium oranges and puree the peel with about 100 ml of distilled water in a blender or food processor. You do not want the fruit pulp. The limonene is concentrated in the peel. 2. Transfer the peel puree to a 500 ml round bottom flask using a widemouth funnel and a stirring rod. You may have to rinse the peel puree into the flask using some DI water. Add enough water of to the mixture in the flask to 2/3's the capacity the flask. Don t add too much water as you do not want the orange peels and water shooting up into the Claisen while boiling! 3. Add a few boiling chips to the mixture. Why do we need these? 4. Set up the distillation apparatus as shown below using a very small amount of vacuum grease to lube the glass connections. Place a wiregause supported by a ring and ring-stand under the receiving flask (just in case the clamps don t hold!). 5. Look over the set-up in the front of the room for the placement of the spring clamps. Also notice that there is one addition clamp in the set-up at the receiving flask. Your heat source will be a hot plate with an aluminum block. 6. Fill the separatory funnel with deionized water. 7. Wrap the claisen and stillhead with aluminum foil. This will keep the steam hot and allow it to keep traveling to the condenser. 8. Have your instructor check your set-up before you proceed. 3

4 9. Turn on the condenser water. 10. Turn on the hot plate to the 8 setting. It will take about minutes for your orange peel puree to boil. 11. What is the temperature at the still head when your mixture starts to boil? The idea is that you want a vigorous enough boiling cause refluxing of the mixture but not so vigorous that it urps into the stillhead! 12. What is the temperature at the still head when you collect your first drop of distillate? 13. As the mixture boils and distills, you will be losing water from the distillation mixture. As the level drops in the flask, add small volumes of water via the separatory funnel. It is important to watch the water level because of the high concentration of sugar in oranges. If the water level gets too low, the sugar will carmelize and burn. It is better to add small amounts of water so that the temperature doesn t drop drastically. 14. Distill and collect about 40 ml of liquid. 15. Turn off the hot plate. Remove the aluminum foil. We will recycle the foil for the next lab. Wait 15 minutes for the system to begin to cool. The distillation will continue during this time. 16. Very carefully remove the receiving flask from the set-up and place it in a beaker. Place a beaker under the vacuum adapter to catch any drips. 17. Add about a half of a gram of NaCl to the distillate. This raises the ionic strength of the water and increases the separation of the two layers. You should be able to observe droplets or a film of the product, limonene, on the surface of the distillate. 18. Obtain a 50 ml burette. Empty the water from the burett. 19. Pour the contents of the flask into the burette. (If you have much more than 50 ml you ll need to do this in batches.) Allow the liquid to settle; all the orange oil should rise to the top of the burette. 20. Carefully read buret to determine the volume of orange oil collected. Ask your instructor for help if you are unsure. About how many ml of orange oil did you collect? 21. Slowly drain off the water until it is all drained out. This aqueous portion of the distillate is called the hydrosol. Save some of the hydrosol in a labeled vial. 4

5 22. Drain the orange oil into a clean, dry, pre-weighed labeled screw-top vial. Reweigh the vial to determine the amount of product. Save this oil for the soap-making lab later on in the semester. 23. Now it s time for clean-up! The orange peel puree can go down the drain. If you can, try to recover the boiling chips. 24. Use the brushes and detergent to clean your distillation set-up. 25. The buret can be cleaned with a few rinses with soapy water, then tap water, and finally DI water. Fill the buret up with DI water and replace the cork. 26. Have your instructor check your washed set up. 5

6 Lab Report Steam Distillation of Orange Oil Chem 306 Name Partners Data A. Physical Properties of Orange Oil 1. Mass of empty labeled vial 2. Mass of labeled vial + orange oil 3. Mass of orange oil recovered 4. Volume of orange oil recovered 5. Density of orange oil (D = M/V) Show set-up and work for density calculation in the space below: Don t forget your units and sig figs! Box your final answer. 6. Is limonene hydrophobic or hydrophilic? Use your observations from this lab and what you know about IMF to explain your answer 7. Does limonene float on water or does water float on limonene? Use your density data and observations above to explain your answer. 8. Use a gently wafting procedure to analyze the odor of the D limonene. Report your observations. 6

7 9. Repeat the above wafting procedure for the hydrosol. a. Report your observations. How does the odor of the hydrosol compare to the odor of the oil? Give a chemical explanation for your observations. b. Hydrosols are used in perfumery and aromatherapy. If available, analyze the odor of lavender essential oil and its hydrosol. What do you think? B. Chemical Properties of Orange Oil 1. What is the chemical formula for D Limonene? 2. Draw the expanded structure of D limonene. Circle the two isoprene units in limonene. 3. Name the functional group found in limonene. 4. Explain the relationship between D and L limonene. How do these two structures differ? How are they the same? Look at the models on display in lab. 7

8 5. What type of isomerism is exhibited by these two compounds? Would you expect L-limonene to have the same characteristics as D limonene? (If a sample of L-limonene is available, use the wafting procedure to analyze its odor. Compare the odor of D and L limonene.) 6. Predict the hydration product of limonene if two molecules of water are added to a limonene molecule. 7. Do you think that limonene is flammable? Dip a metal spatula into your limonene and gently pass it through a flame. Report your observations. C. Limonene as a Hydrocarbon The activities in this lab illustrate some general properties of hydrocarbons. State two of these properties of hydrocarbons. 8