Changes for Organic Chemistry 2521 Labs

Transcription

1 Changes for Organic Chemistry 2521 Labs Chapter 3 Crystallization Part 1 (Starts on page 56) Test the solubility of three compounds with three solvents. There are four compounds to choose from: 1. Resorcinol 2. Anthracene 3. Benzoic Acid 4. 4-amino-1-naphthalenesulfonic acid, sodium salt The solvents to be used are: 1. Water 2. Toluene 3. Hexane (Ligroin) Part 2 (Starts on page 57) One of the three compounds will need to be crystallized. 1. Phthalic Acid 2. Naphthalene 3. Anthracene Your lab TA will tell you which one to do. Part 3 (Starts on page 59) There are no changes for this part. Chapter 4 Melting Points and Boiling Points Melting Points Part 1 (Starts on page 69) You will calibrate the melting point apparatus using naphthalene (melting point o C) To take the melting point you need to make two readings: 1. When the substance begins to melt and 2. When the substance is completely melted. Part 2 (Starts on page 70) Take the melting points of pure urea (m.p o C) and cinnamic acid (m.p o C).

2 Part 3 (Starts on page 71) Take the melting point of a mixture of urea and cinnamic acid. There are three mixtures, your group will only need to do one. The TA will assign this to you. Part 4 (Starts on page 71) Your group will be assigned an unknown. With this unknown you will do a quick determination of the melting point and a slow determination of the melting point. This is explained in the lab text. The TA will assign the unknown to you. Boiling Points A. You will need to calibrate the thermometer. This procedure is found on page 89. This is chapter 5 part 1 (page 89). 1. Test the 0 o C point of the thermometer. 2. Put the thermometer in a ice/distilled water bath. 3. Read the thermometer 4. Test the 100 o C point of the thermometer 5. Put 1 ml of distilled water in the test tube with a boiling chip 6. Use figure 4.8 (page 75) 7. The thermometer must be above the liquid. 8. Read the temperature when it is constant and no longer rising. B. Take the boiling point of 95% ethanol (78 o C). Summary of Ch 4: Melting points: You are doing 6 melting point determinations. Boiling points: You are doing 2 boiling point determinations; one for water the other for ethanol. Answer questions 5, 6, 7, 13 (page 78) Chapter 5 Distillation Part 1 (Starts on page 89) Calibrate the thermometer if you did not do so in chapter 4. Part 2 B (Starts on page 90) You will do B, Simple Distillation of an Ethanol-Water Mixture. Use the small-scale distillation apparatus, figure 5.5. Part 3 B (Starts on page 91) You will do B, Fractional Distillation of an Ethanol-Water Mixture Use the small-scale fractional distillation apparatus, figure 5.6. Answer questions: 9, 10 (page 96)

3 Chapter 8. Isolation of Caffeine from Instant Coffee. 1. In a 25-ml Erlenmeyer flask place: 2g of sodium carbonate (Na 2 CO 3 ) + 2g of instant coffee powder + 9 ml of boiling water. Stir the mixture well. 2. Boil the mixture again using the hot plate. Stir. 3. Pour it in a centrifuge tube, cool to room temperature in an ice bath. 4. Add 2-ml of dichloromethane (methylene chloride) into the centrifuge tube, cap it and shake it vigorously for 1 min. Put it in the centrifuge; run for 3-4 min. 5. Remove the clear yellow part (organic part) from the bottom of the tube using a pipet, and place it in a 10-ml Erlenmeyer flask. 6. Repeat steps 4&5 twice (3 times total!!!). Combine the organic parts in the same Erlenmeyer flask. 7. Add Sodium Sulfate (Na 2 SO 4 ; drying agent) or Calcium Chloride (CaCl 2 ) in portions using your scoopula to the combined organic parts. Shake until it no longer clumps together. Let it dry for about 10 min. 8. Transfer the dried solution to a tarred 25-ml filter flask using a new pipet. Wash the drying agent (Na 2 SO 4 or CaCl 2 ) twice with 2 ml portions of dichlomethane, then evaporate it to dryness (see Fig. 8.7, page 132). It takes about 10 min. The residue is pure caffeine. Determine the weight. 9. Heat the flask on the hot sand for a while (see Fig. 8.12, page 148), do not add ice at this time! Be careful using the water vacuum, make sure you disconnect the tube connected to your flask before stopping the water! 10. When you see the white smoke coming out, add ice into the centrifuge tube. Keep heating until the white smoke disappears. White crystals will form on the wall of the centrifuge tube or the neck of the filter flask. It will take a while! 11. Weight the product on a piece of weighing paper, calculate the % yield. 12. Measure the melting point.

4 Chapter 9 Chromatography Part 2 (Starts on page 162) Changes: 1. Use 1 g. tomato paste (NOT 5 g.) 2. Transfer the tomato paste using 5 ml ethanol (NOT 10 ml acetone) 3. Use a 25 ml Erlenmeyer flask (NOT a 125 ml E-flask) 4. Shake the solid residue with 5 ml dichloromethane (NOT 10 ml) 5. You will keep the layer of liquid that has the most color to it. 6. Do NOT evaporate the dichloromethane solution TLC (Thin-Layer Chromatography) Develop the TLC plate using 70:30 hexane:acetone (NOT 80:20) You will need to obtain the Rf value of the substances on your TLC plate. (page 159) Answer questions: 2, 3 (page 170)

5 Chapter 10 Column Chromatography Part 1 (Starts on page 175) Packing the column (page 173) Make sure your column has a polyethylene frit (fig 10.1). Pour the silica gel into the column so it is 1/2 to 2/3 full. Pour the silica gel out of the column into a beaker (50 ml size) To the silica gel add 8 ml of hexane. Clamp the column in a vertical position. To the column add 2 ml hexane Stir the hexane silica gel mixture, while stirring pour it into the column. Open the valve and drain the solvent. Do not let the solvent level get below that of the silica gel. Repeat step 7-8 until all the silica gel is in the column. close the valve while there is still some liquid on top of the column Making the mixture of ferrocene and acetylferrocene 1. Measure out 45 mg (.045g) of both ferrocene and acetylferrocene. 2. Dissolve the two compounds together in dichloromethane (a few drops) 3. add to this 0.300g silica gel 4. evaporate off the solvent using a hot water bath 5. make sure the liquid in the column is right on top of the silica gel 6. Pour this dry mixture into the column. 7. Follow the procedure in the book You will need to obtain: 1. Weight of crude ferrocene and of crude acetylferrocene 2. Recrystallized weight of ferrocene and of acetylferrocene 3. Melting points of ferrocene and of acetylferrocene 4. Percent recovery 5. TLC

6 Chapter 20 Bromination of Cholesterol Part 1 (Starts on page 296) 1. The solution of bromine and sodium acetate in acetic acid is already made. 2. Stir the crystalline paste for 15 minutes not for 10 minutes. 3. Do NOT use the wilfilter apparatus to filter your product. Part 3 (Starts on page 298) Before you add the 40-mg of zinc dust to the dibromocholesterol activate it. Procedure to activate zinc dust: 1. Measure out g zinc dust, put in a medium sized test tube 2. add 2 drops of water (distilled) 3. add 6 drops of 3M HCl, you should see bubbles if you do not add more HCl 4. let this react for 30 seconds 5. add water until the zinc settles to the bottom of the test tube 6. decant off the water The zinc is ready to be used. Use it RIGHT AWAY! Later when you have to wash the ethereal solution it is best to explain the washings: 1. To the decanted solution from the zinc add 2 ml distilled water. Shake or stir the solution. Pipette off the water layer. If you do not see 2 layers something is wrong. 2. Repeat with 2 ml of water, pipette off water layer. 3. Add 1 ml of 3M NaOH to the ether solution, shake/stir and then pipette off the NaOH layer. 4. Add 1 ml saturated NaCl solution, shake/stir and pipette off the NaCl solution *Note: If you don t know which layer is the ether layer, add more t-butyl methyl ether. The layer that increases is the ether layer. The ether layer is the one you want to keep. End of the lab you will need to obtain: 1. Final weight of product 2. % yield 3. melting point Answer question: 2 (page 300)

7 Chapter 17 Nucleophilic Substitution Reactions of Alkyl Halides This starts on page 272, use the microscale procedure. There are NO changes. Chapter 31 Trityl Methyl Ether and Trityl Bromide Part 1 (Starts on page 395) 1. Do not use any glassware that is wet. 2. When you are stirring and grinding the solid to dissolve all the alcohol do this for 1 hour. 3. Once you cool the solution on ice you will need to scratch the tube with a stirring rod. Keep this in ice. 4. Do not recrystallize Part 2 (Starts on page 396) 1. Start part 2 while you are waiting for part 1 2. If you cannot dissolve the triphenylmethanol in acetic acid, add a couple drops more of acetic acid 3. Do not go on to add the hydrobromic acid until all the triphenylmethanol is dissolved 4. Wash the product with cold hexane 5. Recrystallize the end product 6. Do not do the flame test You will need to obtain: From Part 1 1. Final weight of product 2. % yield 3. melting point of product From Part 2 1. Crude weight 2. % yield using crude weight 3. Recrystallized weight 4. melting point of both the crude product and recrystallized product

8 Chapter 7 Sublimation You each will be working alone. 1. You will need to sublime two known substances and one unknown substance. The TA will assign the 2 known compounds and the unknown to you. 2. If you do not understand the lab refer back to the caffeine lab, in that lab you should have sublimed crude caffeine 3. You will be using figure 7.14 (page 121) 4. Do NOT get water in the apparatus