245 * Lab #4 Steam Distillation of Orange Oil

Transcription

1 245 * Lab #4 Steam Distillation of Orange Oil In this experiment we will be extracting d-limonene (p-mentha-1,8-diene) by use of steam distillation. You want to be able to separate this natural product at a temperature well below its boiling points so that there is little chance of the chemical that you are trying to recover decomposing. Steam distillation is the method of choice when you are recovering reactive, volatile substances that are to be recovered from nonvolatile and or water soluble contaminants. This is a complex distillation apparatus. Remember that you need to support the glassware with enough 3-prong clamps and blue clips to prevent any accidents. Do not use the blue clips at the stillpot /claisen intersection. The heat can ruin the plastic clips. Since we a going to add water to the still pot, your glassware only needs to be cleaned, but not dry (some water may remain in the glassware). You will be using the same heat source (heating mantles) as in the previous two labs. There will be no open flames during this lab. Procedure At home, peel two (2) medium oranges and puree the peel in a blender or food processor. You do not want the fruit pulp. The limonene is concentrated in the peel. Transfer the peel puree to a 500 ml RBFlask. Use a wide-mouth funnel and a stirring rod. Add about 200 ml of deionized water or enough to fill to 2/3's the capacity the flask. You do not want the orange peels and water shooting up into the Claisen while boiling. Set up the distillation apparatus as shown in the laboratory text, replacing the steam tube with a separatory funnel. Diagram shown on next page.

2 Distill and collect ml of liquid. (There is a lot of sugar in oranges so be careful not to burn the solution - you will end up with a flask that is very hard to clean don t forget to add water via the separatory funnel as the water level in the flask drops. It is better to often add small amounts of water from the separatory funnel so that the temperature doesn t drop suddenly.) After collection of the liquid, you should be able to observe droplets or a film of the product, limonene, on the surface of the distillate. Remove the flask and add about a half gram of salt (NaCl) to the liquid. This raises the ionic strength of the water and increases the separation of the two layers. Obtain a burette from the drawer near the balances. 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. Now think of the burette as a long skinny separatory funnel: Slowly drain off the water until it is all drained out. You ll probably lose a few drops of limonene too that s OK. Drain the orange oil into a clean, dry, pre-weighed screw-top vial. Reweigh the vial to determine the amount of product. Perform an IR (CaF 2 plates only!!) and refractive index on your product. If necessary, you may have to combine samples to take an IR and the refractive index if your yield was too low. FT-IR Spectrum of Limonene (courtesy of AIST) WASTE Spill and Disposal - E: Any acetone used to clean glassware. *THERE IS AN ACETONE WASTE JUG IN THE HOOD* DO NOT PUT USED WEIGH BOATS IN THE HW CHEMICAL CONTAINER. CONTAMINATED PAPER TOWELS AND WEIGH BOATS ARE PUT INTO THE CLEAR PLASTIC HW BOX IN THE HOOD. PAPER ENVELOPES W/CHEMICALS SHOULD BE FOLDED MULTIPLE TIMES AND SEALED BEFORE BEING PUT INTO THE SPECIFIED HW CONTAINER.

3 CHEMICALS LOCATION *Acetone Bottles* Hood #4 * Orange peel supplied by students * Acetone w/salt (IR plate cleaner) Hood #5 SUPPLIES 50 ml EMF Organic White Vials & boiling stones FT-IR Spec. & Directions IR Table Holder, IR Cards & salt plates PE Infrared Spectrophotometer & supplies Blue IR Cart (directions below) 1. Monochromator/Photometer and 5. Power on/off switch electronics Compartment 6. Control Panel 2. Recorder pen 7. Sample area 3. Frequency (wavenumber) display 8. Baseline control 4. Source compartment STARTUP 1. Ensure that the sample beam and reference beam are unblocked and then press the Power toggle switch (located on the right side) on. Wait 60 sec's for initialization. Setting the starting wavenumber

4 1. Press Wavenumber. (the wavenumber LED lights) The wavenumber at which the instrument is set will appear on the display. 2. Press Parameter adjust and/or to the desired value. A full scan will start at 4000 cm. Setting the chart paper 1. Press Chart. (the chart LED lights) 2. Press Parameter adjust and/or to the desired value. A full scan will start at 4000 cm. Selecting chart expansion 1. Select chart expansion 1. Selecting a scan time 1. Select a scan time of 3. (3 minutes) Preparing the CaF 2 cells with the cell holder. 1. Clean the salt cells with the special NaCl saturated in acetone solvent and wipe with kimwipes. 2. Arrange the CaF 2 plates in the cell holder in the following order: a. bottom cell holder (the one with the bolts) b. rubber "o" ring or spacer c. first salt plate d.2-3 drops of sample e. second salt plate f. top of cell holder and nuts. Tighten nuts loosely or you will shatter the salt plates. Running the IR Scan 1. Place the cell holder w/sample into the first slot. It will just slide into the slot from the top of the #1 slot area. Make sure that the pen is in the pen holder and that the paper has been adjusted to the correct wavenumber before you start. 2. Adjust the Baseline control to attain the highest transmittance possible (between 80% and 100%). If the transmittance of your prepared cell is below 70% you may want to reprep it. It may be a dirty cell or your sample is opaque. Light waves must be able to travel through your cell preparation or you will get a poor scan.

5 3. Press the SCAN button. The scan will stop at some points to readjust the grating angle and a terrible noise will come from the IR. Don t worry the instrument will begin again. Wait until the full scan has stopped; the paper will advance to the next starting point. 4. Use the provided ruler as an edge to tear your scan from the next. 5. CLEAN YOUR PLATES/CELLS with acetone BEFORE THE NEXT SCAN. Never subject any IR cells to any water ever!!! 6. The instrument should be ready to accept the next scan.