Acids and Bases Protocol, Lab Reports of Chemistry

Download Acids and Bases Protocol and more Lab Reports Chemistry in PDF only on Docsity! Acid-Base Extraction Procedure CHEM 22300 TLC 1. Create a TLC chamber using a beaker and watch glass OR aluminum foil. 2. Obtain a silica TLC plate and mark the starting point of your compounds about 1cm from the bottom of the plate using a pencil (can be indicated on a line or with a single dot). 3. Prepare 5mL of a 95% ethyl acetate 5% acetic acid solvent system (5mL*0.95=4.75mL ethyl acetate; 5mL*0.05=0.25mL and pour into TLC chamber. Be sure to cover when not in use! Solvent will evaporate otherwise. 4. Dissolve small amount of acetylsalicylic acid and phenacetin mixture using limited amount in methylene chloride AKA dicholormethane AKA DCM. 5. Using a capillary tube, dip into dissolved mixture and spot onto TLC plate. (Spot the plate by quickly touch the capillary tube onto the plate, remove, allow to dry, and repeat until no more solution is remaining in capillary tube.) 6. Repeat steps 5 and six, but substitute the acetylsalicylic acid and phenacetin mixture for pure acetylsalicylic acid and then phenacetin. 7. Carefully place TLC plate into chamber and allow to develop. Remove plate when solvent has traveled about 1/2cm from the top of the plate and mark with line the level the solvent had reached on the plate. 8. Measure the distance traveled by each solute and the distance traveled by the solvent and document in lab notebook. Take a picture of the TLC plate. (This will be used to calculate Rf values on your report.) Extraction 1. Set up ring stand with a ring, place small separatory funnel, close the stopcock (it should be perpendicular to the sep funnel spout), and make sure you have appropriate size ground glass stopper. 2. Label three 250mL Erlenmeyer flask, one for bottom initial organic layer, one for top aqueous layer, and one for final organic layer. (DCM is more dense than H20.) 3. Weigh out 3g of acetylsalicylic acid and phenacetin mixture, record the actual weight, and place in small Erlenmeyer flask (~50mL) 4. Dissolve acetylsalicylic acid and phenacetin solution in 30mL of DCM. 5. Add 50mL of saturated sodium bicarbonate (NaHCO3) to sep funnel. 6. Transfer dissolved acetylsalicylic acid and phenacetin solution into sep funnel, rinse flask with 5ml of DCM and pour into sep funnel. 7. Put the ground glass stopper into the sep. funnel, pick it up, invert it with your hand cupped over the stopper to insure it stays in the sep. funnel, and open the stopcock to vent any pressure. Venting is especially important when using bicarbonate, as CO 2 is generated when mixed with acids. 8. Cautiously alternate shaking and venting until little, if any gas, escapes, then shake more vigorously and vent a few times. 9. Put the sep. funnel back in the ring, remove the stopper (as is always done immediately), and allow the liquid phases to separate completely. 10. Drain the lower organic layer into a 250 mL Erlenmeyer flask. Make sure you follow the meniscus (the line between the two liquid layers) and stop when it gets to the stopcock. Save this flask to be dried later. a. At this point the aqueous layer remains in the sep funnel containing sodium salt of carboxylic acid, and the organic layer contains the phenacetin. 11. Transfer aqueous layer to Erlenmeyer flask. Slowly add ~75 mL of 1 M HCl with mixing (swirl gently) to the flask containing the aqueous bicarbonate solution containing the sodium salt of your carboxylic acid. YOU MUST ADD IT SLOWLY, ESPECIALLY AT FIRST, AS CO2 GAS WILL BE GENERATED and can foam out of the flask. 12. Test the pH of your aqueous solution with litmus paper to ensure that it is acidic. If it isn't, add another 5 mL of 1 M HCl, mix, and retest the pH. 13. Add 5mL DCM to the Erlenmeyer flask contain the now acidic aqueous solution, transfer to sep funnel then set it in the ring stand to settle. You may have to add more DCM. 14. Drain out the lower organic layer and upper aqueous layer. 15. Return the remaining DCM layer to the sep funnel and wash with a small portion of brine (saturated NaCl). 16. Drain out the brine after it has settled, and then drain the DCM into a dry Erlenmeyer flask. 17. Preweigh 2 round bottom flask and label one. acetylsalicylic acid and the other phenacetin. Record weights in notebook! 18. Add some solid, anhydrous Na2SO4 to the organic layer containing phenacetin and the other organic layer containing acetylsalicylic acid a d swirl off and on for a few minutes. If all the drying agent clumps, add more and continue swirling. 19. Filter the individual layers of DCM through filter paper in a funnel into a round-bottom flask, washing with extra DCM.