Ex. 6 - Steam Distillation (2020) PDF

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EXPERIMENT 6 MICROSCALE ISOLATION AND CHEMICAL TESTING OF CLOVE OIL PURPOSE: In a steam distillation, it is desired that an oil that otherwise will not readily distill alone or dissolve in water can simultaneously boil with water as an azeotrope at a reasonable temperature and in a fixed ratio. Thus a particular ratio of the oil and water will be collected as the distillate and extraction can be used to isolate the oil. There are many variations in equipment setup that could potentially be used. In this experiment a microscale setup will be used with the Hickman stillhead and all necessary water will be added before the distillation is begun. The presence or absence of unsaturation will be tested using a dilute bromine solution (Br2 in CH2Cl2). In this chemical test, one of two results is possible: Result A- bromine does NOT react with substancesubstance + bromine  same substance + bromine (colorless) (red-brown) (still colorless) (still red-brown) Thus one observes that the addition of bromine turns colorless solution red-brown Conclusion: the substance did not contain a functional group that reacts with bromine Result B- bromine DOES react with substance substance + bromine  brominated substance (colorless) (red-brown) (still colorless) Thus one observes that the addition of bromine to a colorless solution results in the solution remaining colorless Conclusion: the substance reacted with bromine

READ ABOUT: Read Techniques in Organic Chemistry on Steam distillation (page 164 - 166) and use of a Hickman Still for miniscale distillation (page 161). The major constituent of clove oil is eugenol. This compound is largely responsible for the smell and taste associated with cloves. Look up the structure, physical properties, and safety data of methylene chloride, bromine and eugenol and include them in your prelab write-up (along with the citation- not wikipedia).

PROCEDURE: Isolation of eugenol Use a mortar and pestle to crush about 0.50 g (record exact amount) of clove buds, or use ground cloves “as is.” Transfer them to a 50mL round bottomed flask with 25 mL of water and a stir bar. Affix a Hickman stillhead (get one from the front bench) and a water-cooled condenser and place apparatus in a heating mantle on a magnetic stirrer. Allow the water to soak into the cloves so that it is thoroughly wet. Once wet, begin heating to achieve a steady distillation, but not too hot so that bumping and frothing is avoided. The distillate will collect in the side pocket of the Hickman still. Use a pasteur pipette to occasionally remove distillate during the distillation. Transfer the distillate to a screwcap tube or vial until 5-8 mL has been collected. To extract the oil, use a pipette to add 2.0 mL of methylene chloride to the distillate. Cap the tube and shake vigorously (with venting). Allow the layers to separate and remove the bottom (organic) layer using a pipette and transfer to a clean, dry (conical) vial. Repeat the extraction twice more with fresh 1 mL portions of methylene chloride. Remove any visible drops of water using a pipette and then dry for 10 minutes (with occasional mixing) with anhydrous sodium sulfate. Use the “right” amount of sodium sulfate by looking for the persistence of anhydrous salts (loose and granular). Transfer the solution without the solids into a pre-weighed vial and measure the total weight. Perform the chemical test.

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Analysis For the chemical test, add a single drop of 2% bromine solution to your sample and note the color of the resulting solution. In all likelihood your sample is initially colorless and the bromine solution is initially a red-brown color.

Report: Formal lab report as described in the report guidelines handout due next week in the appropriate dropbox on D2L. The following guidelines are merely recommendations of things to cover, not the limits. Theory: - Explain how steam distillation works and what principles allow us to distill clove oil (boiling point of 254°C) at a little over 100°C. Results: -

Report the mass of product isolated. Cloves are 17% eugenol by weight. Calculate the theoretical yield and % recovery. Show all work to receive credit. Since we are reacting eugenol with bromine to determine if we successfully isolated the compound, a chemical equation for the reaction is required. Use a chemical drawing program to insert the image into your document. o Below is an example of reaction between alkene (double bonded hydrocarbon) and bromine. Br + Br 2 o

Br

Discussion: - Is steam distillation an effective way to extract eugenol from cloves? - Discuss the purity of your eugenol. - In broad terms, discuss how large a component of the mixture eugenol is.

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