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Chemistry 354 Organic Chemistry Laboratory I

Chemistry 354 Organic Chemistry Laboratory I. Safety. The organic chemistry safety presentation on the web is available on the web at the following address:

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Chemistry 354 Organic Chemistry Laboratory I

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  1. Chemistry 354Organic Chemistry Laboratory I WWU -- Chemistry

  2. Safety The organic chemistry safety presentation on the web is available on the web at the following address: http://atom.chem.wwu.edu/dept/osafety/index.htm. Read pp 542 – 558 in the lab book. We administer the safety quiz online at the following URL: http://argon.chem.wwu.edu/SafetyQ/OCQLink.htm A link to the safety quiz is included at the bottom of the instruction page. You will have 30 minutes to complete the 25 question quiz. WWU -- Chemistry

  3. Safety First Try: Tuesday, June 20, 8AM to Friday, June 23, 10AM Second Try: Tuesday, June 20, 8:00 AM to Friday, June 23, 10 AM Third Try: Tuesday, June 20, 8:00AM to Friday, June 12, 10 AM In order to be enrolled in this course, each student will be required to take and pass a laboratory safety quiz. You must pass the quiz before Tuesday, April 6th at NOON. If you cannot successfully pass the quiz, you will be dropped from this course. WWU -- Chemistry

  4. Chemistry 354 Lecture • Purpose: To ensure that each student, regardless of laboratory section and instructor, receives the same information in preparation for the experiment. • Examinations: The midterm and final examinations will be given in this lecture session. WWU -- Chemistry

  5. Introduction to Microscale Laboratory • Read: • Experiment 1 (pp. 2 – 13) • Technique 1 (pp. 542 – 558) • Technique 2 (pp. 558 – 565) • Technique 3 (pp. 566 – 573) • Technique 4 (pp. 574 – 580) WWU -- Chemistry

  6. Introduction to Microscale Laboratory • Macroscale: Quantities of chemicals on the order of 5 to 100 grams. Glassware containers up to 500 mL. • Microscale: Quantities of chemicals on the order of 0.050 to 0.100 grams. Glassware containers up to 25 mL. WWU -- Chemistry

  7. Introduction to Microscale Laboratory • Heating • No flames • Dispensing of liquids • Assignment: • Laboratory exercise 1 (parts A and B) • Laboratory exercise 2 • There is no pre-lab or laboratory report required for this assignment- WWU -- Chemistry

  8. Experiment 2: Solubility • Reading Assignment • Experiment 2 (pp.13 – 20) • Technique 5 (pp. 581 – 589) • Technique 10 (pp. 637 – 646) WWU -- Chemistry

  9. NOTE: You will be expected to submit a pre-lab assignment before you begin this experiment! • Consult the syllabus for your laboratory section for the due date for the pre-lab exercise and for the final laboratory report. WWU -- Chemistry

  10. Solubility • The extent to which a substance is soluble in a solvent. • Examples (solubility in water at 25°C): • Cholesterol 0.002 mg/mL • Caffeine 22 mg/mL • Citric acid 620 mg/mL WWU -- Chemistry

  11. Solubility -- Definitions • Solute: The substance that is being dissolved • Solvent: The medium in which the solute is being dissolved. • NOTE: In a solution, the solvent molecules greatly outnumber the solute molecules. WWU -- Chemistry

  12. If a liquid organic compound is dissolved in a solvent… • Miscible: solute and solvent mix homogeneously in all proportions • Immiscible: solute and solvent do not mix; they form two separate liquid phases WWU -- Chemistry

  13. Part A: Solubility in a Series of Solvents WWU -- Chemistry

  14. Some hints on doing the solubility lab: • You can do the various parts of the experiment in • any order you wish! This eliminates lineups by the • Balances. Part A is especially time consuming! • Be sure to approximate the amounts of solids you • are using in Part A. You don’t need to be exact • on the weights. WWU -- Chemistry

  15. You will study the solubility behavior of benzophenone, malonic acid, and biphenyl in: Water, methanol, hexane How does the polarity of the solute influence the solubility in each of these solvents? What factors are at play, here? WWU -- Chemistry

  16. Make a guess as to the solubility of malonic acid in water. Notice that the acid has two very polar carboxyl groups in the compound. Would you expect this compound to be soluble in the non-polar hexane solvent? WWU -- Chemistry

  17. How consider the solubility of biphenyl in water. Make a guess as to the whether it will be soluble in water. What about the solubility in hexane? WWU -- Chemistry

  18. Solubility Rule “Like Dissolves Like” WWU -- Chemistry

  19. Why Does The Rule Work? • If a substance is to dissolve in a solvent, the intermolecular attractions between solute molecules and solvent molecules must be similar in strength as the solute-solute and solvent-solvent intermolecular attractions. WWU -- Chemistry

  20. Types of Intermolecular Attractions • Dipole-dipole attractions • Hydrogen-bonding • Van der Waal (London) forces WWU -- Chemistry

  21. Solutes: Solvents Water Hexane Part B. Solubility of Different Alcohols WWU -- Chemistry

  22. All three of these alcohols have a polar hydroxyl group. However, the rest of the molecule has a non-polar hydrocarbon chain. WWU -- Chemistry

  23. How does the length of the carbon chain influence the solubility of the test alcohol in water? How does the length of the carbon chain influence the solubility of the test alcohol in hexane? What accounts for any differences? WWU -- Chemistry

  24. Part C. Miscible or Immiscible Pairs • Here we examine pairs of compounds to determine whether or not they are miscible (soluble). • How do differences in polarity affect solubility? • How do intermolecular attractions influence the solubility of a solute in a particular solvent? WWU -- Chemistry

  25. Part D. Solubility of Organic Acids and Bases • Solutes: WWU -- Chemistry

  26. What is the important component in 1.0 M NaOH? What is the important component in 1.0 M HCl? What principle explains the solubility of a substance in aqueous acid or aqueous base? WWU -- Chemistry

  27. Many covalent organic molecules are not very soluble in water even if they are somewhat polar! Benzoic acid is an example. When benzoic acid is reacted with sodium hydroxide, it is converted to an ionic substance (sodium salt), The ionic substance is now much more soluble in water! Ionic substances are very polar! WWU -- Chemistry

  28. When benzoic acid reacts with sodium hydroxide, what happens to the covalent molecule? WWU -- Chemistry

  29. Benzoic acid is converted to an ionic compound! Ionic compounds are soluble in water! WWU -- Chemistry

  30. Compounds with amino groups are basic. They will become ionic when reacted with an acid because the lone pair on the nitrogen atom becomes bonded to a proton which creates an ionic substance. WWU -- Chemistry

  31. So, what would you expect for the behavior of ethyl 4-aminobenzoate in acid solution and basic solution? WWU -- Chemistry

  32. Remember This… • Ionic compounds are usually very soluble in water. Consider Na+ Cl- • Higher molecular weight compounds with covalent bonds are usually insoluble in water • If the covalent compound can be converted to ions, it will dissolve in aqueous solution! WWU -- Chemistry

  33. Part E. Critical Thinking Application • Skip this section WWU -- Chemistry

  34. Experiment 3: Crystallization • Reading Assignment: • Experiment 3 (pp. 21-32) • Technique 6 (pp. 589-597) • Technique 7 (pp. 598-616) • Technique 8 (pp. 616-627) • Technique 9 (pp. 627-637) • Technique 11 (pp. 647-668) WWU -- Chemistry

  35. Experiment 3 • Note that this is a two-day experiment • Plan on using your time as follows, or as your instructor suggests: • First day: Part A and part B • Second day: Part C WWU -- Chemistry

  36. Experiment 3 • NOTE CAREFULLY: • Although the textbook does not say to submit your samples with your laboratory report, the laboratory report sheet does! • Be sure to submit your purified samples of sulfanilamide and fluorene in separate labeled vials. WWU -- Chemistry

  37. Experiment 3 • If you do not obtain 150 mg of sulfanilamide crystals for Part A or 45 mg of crystals for Part B, expect to repeat the procedure until you get it right. • The key is to figure out how to get crystals to form using the minimum amount of solvent. WWU -- Chemistry

  38. Experiment 3 • There is a pre-lab exercise that is due to your instructor before beginning this experiment. The 4th edition of the textbook doesn't have the data for sulfanilamide (although you could guesstimate from the graph on page 648, figure 11.2). Use the following data, instead: • 0 deg -- solubility 14 mg/mL • 20 deg -- solubility 24 mg/mL • 40 deg -- solubility 46 mg/mL • 60 deg -- solubility 88 mg/mL • 78 deg -- solubility 210 mg/mL WWU -- Chemistry

  39. Consult your section’s syllabus for the due date for post-laboratory report. Remember to submit the samples with your laboratory report! WWU -- Chemistry

  40. Part A. Semimicroscale Crystallization • Use an Erlenmeyer flask and Hirsch funnel • Part B. Microscale Crystallization • Use a Craig tube • Part C. Selecting a Solvent to Crystallize a Substance • Part D. Critical Thinking Application • Skip this section WWU -- Chemistry

  41. WWU -- Chemistry

  42. Semimicroscale crystallization using vacuum filtration: Part A WWU -- Chemistry

  43. Microscale crystallization using a Craig Tube: Part B WWU -- Chemistry

  44. Craig Tube + Centrifuge Tube WWU -- Chemistry

  45. Saturated: The solution contains the maximum amount of solute that it can hold at that temperature. No more solute can be dissolved. Unsaturated: The solution contains less than the maximum amount of solute that it can hold at that temperature. More solute can be dissolved. Supersaturated: The solution contains more solute than the maximum amount of solute that it can hold at that temperature. A supersaturated solution is unstable; a precipitate (or crystals) is likely to form if the solution is disturbed. Solubility – Types of Solutions WWU -- Chemistry

  46. Crystal Formation • A dissolved material will separate from the solution as it is cooled. • If the crystal growth is slow and selective, that is crystallization • If the crystal growth process is rapid and nonselective, that is precipitation. • In crystal growth, molecules arranged themselves into a highly specific structure called a crystal lattice. WWU -- Chemistry

  47. Crystal Formation • A successful crystallization depends on a large difference between the solubility of a material in a hot solvent and its solubility in the same solvent when it is cold. • A material can be purified by crystallization when both the desired product and the impurity have similar solubilities, but only when the impurity represents a small fraction of the total solid. WWU -- Chemistry

  48. Solubility versus Temperature WWU -- Chemistry

  49. Solubility of Sulfanilamide in 95% ethanol-water WWU -- Chemistry

  50. What Are The Characteristics of a Good Crystallization Solvent? • There should be a large difference in solubility between hot and cold solvent • The boiling point of the solvent should be well below the melting point of the solute. • The solvent must not react with the solute • The solvent should have a low boiling point (makes removal of the solvent easy) • The solvent should be non-toxic • The solvent should be innocuous • The solvent should not be expensive WWU -- Chemistry

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