Pre-lab 6: Saponification; Synthesis of Soap

Transcription

1 Name: Pre-lab 6: Saponification; Synthesis of Soap Section: Read the background information and answer the following question before lab. 1. What two reactants are used to produce soap? 2. What is the NaCl used for in the soap making process. ~ 70 ~

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3 Lab 6: Saponification; Synthesis of Soap Objective: The objectives of this experiment are to make soap using the saponification reaction. Background Information: Synthesis of Soap Today when we need soap to wash dishes, hair, clothes, the dog or ourselves, we simply go to the store and purchase a product made especially for that purpose. We never stop to think just how lucky we are to be able to buy specific products, ready to use with no contaminants. Not all that long ago, in the times of our great grandparents, if you wanted a product to use to wash things with, you had to make it yourself. And that same product was used for all washing. The soap made at that time was a lye soap, cooked up by reacting fat or oil with lye. Lye or caustic soda are the old terms for sodium hydroxide. Lye was often produced by adding water to ash from the fireplace, and the most common source of fat was probably hog lard. Figure 1. The fat and lye solution were mixed together in a large kettle and cooked over a fire or stove with constant stirring while the water was cooked out of it. After the water was boiled out, and the mixture cooled forming a waxy solid, a solution of plain salt, NaCl, was used to wash it. Making soap, saponification, involves a reaction of sodium hydroxide and a fat or oil to produce glycerol and soap. The reaction is shown in Figure 1. The reaction in Figure 1 shows a fat with only the fatty acid palmitic acid. The oil we will use in lab today is cottonseed oil that contains three different fatty acids. These fatty acids are linoleic acid, oleic acid, and palmitic acid. The condensed structural and line formulas for all three fatty acids are shown in Figure 2. Palmitic acid ~ 72 ~

4 Oleic acid Linoleic acid Figure 2. Procedure: Equipment list: ml beakers 100 ml graduated cylinder 25 ml graduated cylinder Stirring rod Ring stand 2 medium rings Crucible tongs Glass funnel Filter paper Synthesis of Soap 1. Measure out 10 ml of cottonseed oil using a 25mL graduated cylinder. 2. Pour the oil into a 100 ml beaker. 3. Add to the beaker 15 ml of 20% sodium hydroxide and mix well with a stirring rod. 4. Bring the mixture in the beaker to a boil using a hotplate. (If the hotplate is not covered in aluminum foil, place a place of aluminum foil over the heating surface before you heat it.) 5. To avoid splattering, stir vigorously. 6. If you need to take a break or check to see if the reaction has completed, take the beaker off the hotplate and continue stirring until the mixture stops boiling. 7. Stir the mixture with the stirring rod before returning it to the heat. 8. Boil the mixture until all of the water is has boiled off. When the reaction is almost complete the mixture will get very thick and you may need to remove it from heat intermittently to keep it from burning to the bottom of the beaker. 9. Once the water has been removed, let the mixture cool slightly. Check the mixture, if there is a waxy solid forming the reaction is complete. If the mixture is still the consistency of a thick syrup you will need to boil it longer. 10. When the reaction is complete, let the mixture and the beaker to cool. ~ 73 ~

5 Cleaning the NaOH Out of Your Soap 1. Put 18g of NaCl in a 100 ml beaker. 2. Add 60 ml of distilled water and stir with the stirring rod. 3. Once the soap mixture cools to room temperature, add 20 ml of the NaCl solution that you just made. 4. Stir the mixture and break up the larger chucks of soap. 5. Use a glass funnel and filter paper to separate the liquid from the solid soap. 6. Scrape the soap off of the filter paper back into the beaker and repeat steps 3-5 two times. 7. After the third washing and filtering, scrape the soap off of the filter paper onto a paper towel and pat the soap to remove the moister. 8. Press the soap into a bar. If you wish to take it home. Put it in a baggie. 9. When you get home, leave the soap out to cure for at least 6 weeks. Test the soap with a small amount of soap on a small patch of skin before using it to make sure all of the NaOH is gone. You may want to cover it with a towel while curing. ~ 74 ~

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7 Name: Lab 6: Saponification; synthesis of Soap Report Sheet Partner(s): Section: Additional Questions and Exam 2 Review 1. Give the common and IUPAC name for the following compounds: a) b) c) d) 2. Name the following organic compounds: a) ~ 76 ~

8 b) c) d) 3. Are the following compounds soluble, slightly soluble, or insoluble? a) b) c) d) ~ 77 ~

9 4. Is the carbon with the star chiral or achiral? e) * f) * * g) 5. Draw the condensed structural formula of the product of each of the following reactions: Name each reactant and product. a) b) c) ~ 78 ~

10 d) e) f) 6. What type of monosaccharide Are the following carbohydrates? (ex: aldopentose) ~ 79 ~

11 7. Glucose is shown below: which isomer (L- or D-) is it? Draw the α- and β- Haworth structure. 8. Soap has a water attracting end (hydrophilic) and a water repelling end (hydrophobic), how does each end contribute to cleaning oil or grease? ~ 80 ~

12 9. Are the following fatty acids saturated, monounsaturated, and polyunsaturated? a. b. c. d. 10. Identify each part of the following phospholipid as: (a) glycerol (b) fatty acid (c) phosphate or (d) nitrogen base 11) Which of the following has the general structure shown here: a) Steroids b) Carbohydrate c) Fatty acid d) Fats/oils ~ 81 ~

13 12. Explain how tran-fats are created and answer the following question. If the list of ingredients on a product says that it contains partially or fully hydrogenated vegetable oils, does the product have trans-fats? 13. Are the following fatty acids oils or solids at room temperature? a) b) c) d) 14) True or False. The hydrophobic nature of lipids has many important biological consequences. ~ 82 ~

14 15) transport cholesterol to the tissues, they are also responsible for depositing extra cholesterol in the arteries in the form of plaque. pick up cholesterol from the tissues and carry it to the liver to be converted to bile salts and excreted. a) Hormones, steroids b) HDLs, LDLs c) Fatty acids, simple lipids d) LDLs, HDLs 16) In this diagram of a cell membrane, the object labeled A is: a) Cholesterol b) Hydrophobic groups c) Proteins d) Hydrophilic groups 17) When molecules or ions move through the cell membrane from a high concentration to a low concentration without energy, it is called: a) Diffusion b) Protein transport c) Active transport d) Facilitated diffusion **Also study types of lipids, hydrogenation reactions, types of polysaccharides, and acetal bonding to make disaccharides** ~ 83 ~