Experiment C. Acid-Base Extraction: Benzoic Acid, 4-Nitroaniline, Naphthalene

Transcription

1 rganic hemistry I Lab HEM 2211L (Spring 2008) School of Science & Technology Georgia Gwinnett ollege Experiment. Acid-Base Extraction: Benzoic Acid, 4-Nitroaniline, Naphthalene 1. EXPERIMENTAL BJETIVES: a. Use extraction techniques to isolate an acid, base, and neutral compound. b. haracterize and analyze products. c. Present, analyze, and discuss results in a written report. 2. SPEIAL INSTRUTINS: a. omplete the pre-lab outline (below) and prepare your lab notebook before coming to lab. b. Before you will be allowed to begin the experiment, you must have completed lab report sections up to procedures as described in your Instructions for Students in rganic hemistry (IS). All procedures, data, and observations must be recorded directly into the laboratory notebook as part of the report. c. hemicals and solvents: (1) Benzoic Acid, [ ] (2) naphthalene, [ ] (3) 4-nitroaniline, [ ] (4) dichloromethane, [ ] Page 1 of 7 1/7/08

2 rganic hemistry I Lab School of Science & Technology HEM 2211L (Spring 2008) Georgia Gwinnett ollege 3. PRE-LAB UTLINE: 1. The following acid-base reactions will be employed and exploited in this experiment. omplete the following table by recording the solubility of the given compound in both water and diethyl ether (based on the data you gather for your UToRP). Then, draw the structure of the product of the reaction (in some cases, there will be no net reaction) and predict the solubility of the product in water and ether [indicate your prediction as either s (soluble) or i (insoluble)]. Remember the three most important words in organic chemistry: Like dissolves like (polar solvents will dissolve polar and ionic compounds). Rxn ompound in H 2 in Et 2 Reactant/ Reagent Product in H 2 in Et 2 a. i s Hl (aq) no rxn H b. H 2 N N 2 i s Hl - l + H (aq) 3 N N 2 s i c. Hl (aq) d. e. NaH (aq) H H 2 N N 2 NaH (aq) f NaH (aq) Page 2 of 7 1/7/08

3 rganic hemistry I Lab School of Science & Technology HEM 2211L (Spring 2008) Georgia Gwinnett ollege. ompound in H g. - Na + in Et 2 2 Reactant/ Reagent Hl (aq) Product S olubility in H in Et 2 2 h 2 N NH 3 l Hl (aq) same as c. Hl (aq) i. j. 2 N - Na + NH 3 l NaH (aq) NaH (aq) same as f. NaH (aq) Page 3 of 7 1/7/08

4 rganic hemistry I Lab School of Science & Technology HEM 2211L (Fall 2007) Georgia Gwinnett ollege 2. As part of the experiment, you will add NaH or Hl to the solution containing these three compounds and ether. Based on your input above, in which phase (organic or aqueous) will each component (to include solvents and spectators) of the solution be found for the following additions? Note: these are not necessarily the actual additions you will perform. You may use whatever abbreviations you choose, as long as you provide a key to them (e.g., φ 2 H for benzoic acid, etc.) and show the part of the molecule or ion which has undergone a reaction. a. H H H 2 N N 2 H 2 N N 2 Hl (aq) NaH (aq) Draft Page 4 of 7 1/7/08

5 rganic hemistry I Lab School of Science & Technology HEM 2211L (Fall 2007) Georgia Gwinnett ollege b. - Na + - Na + - l + H 3 N N 2 - l + H 3 N N 2 Hl (aq) NaH (aq) Draft Page 5 of 7 1/7/08

6 rganic hemistry I Lab HEM 2211L (Fall 2007) School of Science & Technology Georgia Gwinnett ollege 4. PREDURES: Apparatus 1. Begin cooling two small test tubes of distilled water in an ice bath for later use in rinsing products in the Hirsch funnel. 2. You will start out using your centrifuge tube with cap rather than the conical vial. The three component mixture and dichloromethane all go into the centrifuge tube initially. 3. Use a Hirsch funnel connected to the sink aspirator for vacuum filtration. 4. Use the sand bath in your hood for flameless heating, with aspirator if needed. Dissolution 5. Liquid reagents throughout the lab are approximate so you may use the calibrated plastic, disposable pipets. 6. Use 4 ml of dichloromethane rather than 3 ml noted in your text. 7. ap your centrifuge tube and then use the vortex mixer to mix. It takes a while, but all of the solid should go into solution. Extraction 8. Use three extractions with 3 M Hl rather than the two extractions noted in your text. 9. Use two extractions with 3 M NaH rather than the one extraction noted in your text. 10. At the end of the extraction, leave your organic layer in the centrifuge tube rather than transferring it to a clean test tube. Precipitating and Drying 11. Rather than the drying technique described in the text, dry the "Neutral ompound" by running it through a Pasteur filter pipet filled with anhydrous sodium sulfate and into your 5 ml conical vial. After drying, evaporate the solvent in the hood in the warm sand bath and aspirator as needed. Do not heat too vigorously or your product will bump out of the vial and into your sand. If all of the solvent does not come off during the first lab period, mark your vial and store it uncapped until the second lab period. Draft Page 6 of 7 1/7/08

7 rganic hemistry I Lab HEM 2211L (Fall 2007) School of Science & Technology Georgia Gwinnett ollege 12. Use small pieces of ph paper on a glass evaporating dish ( watch glass )to test ph of your Hl and NaH extract solutions as you neutralize them with the 6 M NaH and 6 M Hl. You may need to use your spatula to stir the mixture during neutralization. 13. Skip the procedure of... "Rinse each solid back into its respective test tube..." and instead vacuum filter the contents of the test tubes using the Hirsch funnel. Make sure you wet the filter paper and have good vacuum before dumping your test tube contents into the funnel. Be careful not to overflow the filter paper by pouring too much liquid into the funnel at a time. Wash each solid precipitate as you collect it in the Hirsch funnel with several 1.0 ml aliquots of cold distilled water (# 1 above). You may need to add an additional 1mL of water to the test tube to recover more product if some remains behind after the first transfer. Then transfer each washed solid from the filter paper to a labeled, pre-weighed container. You will store these solid products uncapped until the second lab period. 14. You will not recrystallize your products. 15. At this point you have isolated your three solid compounds. Allow them to air dry, uncapped until you return for the next lab session. Analysis 16. Determine mass % and mole ratio of each of the three components in the original mixture. 17. onduct melting point analysis of benzoic acid, naphthalene and 4-nitroaniline. 18. Determine product recovery (%). Draft Page 7 of 7 1/7/08