organic chemistry lab report

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aspirin synthesis lab report

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The following is a list of things you should bear in mind when you compose a lab report using Microsoft’s Word program: 1. Use 12 point font with normal (1") margins on all sides. 2. Number all pages in sequential order. 3. The date shall be the actual date when your experiment was performed. 4. Separate sections with appropriate sub-headings (bold or italic); and staple all pages together. 5. Your and your partner’s names must be on the report in the following format: XXX (your name) Partner: YYY (partner name) 6. If it’s an experiment of technique (such as melting point measurement), show the chemical structures for all the compounds you actually used in the experiment. If it’s a reaction, show the reaction scheme but not individual structures in the first page. You must draw the structures/schemes by yourself using appropriate software such as MarvinSketch, Accelrys, or ChemDoodle. Direct copy of images from your eChapters, Internet or any electronic resources is not allowed. 7. For reference specify the edition and full page range of the lab textbook. (This requirement is different from the example section F on page 21 of the textbook.) 8. For scientific report the smallest details, such as punctuation, need to be as accurate and correct as possible. Convention must be followed. The grammar must be checked. Each occurrence of minor error will result in 5 points reduction. You will receive some leniency for first-time mistakes, but each recurring minor error will result in full 5 points deduction. 9. All measured values must have an appropriate unit. Have one o space between any value and its unit, such as 132 – 133 C. Use o symbols/abbreviations for the units, such as C instead of degree Celsius and g instead of gram. Common units: g, mg, mol, mmol, o mL, L, C, mm, cm, m, h (for hour), min (for minute), s (for second). The values should also have correct significant numbers. Thus 0.1350 g (measured from a balance) should not be recorded as 0.14 or 0.135 g, and 1.04 mL (measured from a graduated cylinder) should not be recorded as 1.0 or 1 mL. 10. Chemical names are like other nouns. Don’t capitalize them unless they are at the beginning of a sentence. Unlike elsewhere in a sentence, there should be no space after a comma in chemical names, e.g. 1,2-dichloromethane. This is a convention for chemists. Similarly, it should be “iron(III) chloride” but not “iron (III) chloride”. The atom symbols in chemical names needs to be capitalized and italic, such as N,N-dimethylaniline. Prefixes such as “tert”, “meta”, “m”, “ortho”, and “para” need to be italic as in “t-butyl chloride” or “m-xylene”, and they are not capitalized at the beginning of a sentence, e.g. “m-Xylene was used...”. Page 1 11. Procedure: Rephrase the procedures in the textbook using past tense (the action was already done) and passive voice (focus on the action not the doer) for the lab reports. This requirement is different from the example section I on page 22 of the textbook. Quite often we made omissions/additions/modifications to the procedures on the textbook, and in your lab report you should write only the modified procedures. You can write up simplified steps for pre-labs (R on page 25 of the textbook) but only normal paragraphs (see I-K on page 22) should be adopted for lab reports. Wrong format in your Procedure section will result in 10 points deduction. Wrong: Crush the sample into fine powder using a spatula. (instruction format, present tense) Wrong: We crushed the sample into fine powder using a spatula. (active) Correct: The sample was crushed into a fine powder using a spatula. (past tense, passive voice) 12. Observations: faithfully record what you actually did in the experiment. Any data (weight, volume, temperature, time, etc.) and phenomenon (color change, cloud, smoke, bubbling, heat generation, etc.) must be reported. Do not repeat what was already said in the “Procedure” section, although you may have to briefly mention which part of the procedure it was in relation to the observation. Report any accidents and spills. Past tense and passive voice should be used. 13. Yield calculation: for chemical reactions you must show the balanced equation, determine the limiting reagent, and calculate the theoretical and actual yields. The quantity of the starting materials should be what you actually measured (such as 76.9 mg) but not just what the textbook says (such as 75 mg). The yields should be rounded to an integer, e.g. 53% instead of 52.88% or 52.9%. Yield calculation which is wrong or lacking details will result in up to 20 points reduction. The yield you get will not affect your report grade significantly. Too high (> 100%) or too low (< 30%) yield will result in 10 points reduction, in which case you should rationalize it in the “Discussion and Conclusions” section. 14. The reaction mechanism should be drawn by software (such as MarvinSketch, Accelrys, or ChemDoodle) if it has been discussed during our lectures or in in your lab textbook. 15. Discussion and Conclusions You can include things like trends in the data, data interpretation, relevance of the experiment or the technique, and what you have learned. To elaborate using an example: Background material. Define melting range. What happens on a molecular level during melting? Data trends and interpretation. Any trends on the data? Is the data as expected? Explain the theory and principle behind the expected trend in the data. If it is not, what are sources of errors? o The melting point (mp) we obtained for pure urea is which is close to the literature value of . Page 2 o Mixtures have lower mp and broader mp range than the pure substances because . Our data is as follows: and is consistent with this expected result. What would be an application of this technique or data trend? (e.g. identification, determination of purity) Summarize the success (or failure) of the experiment. Describe what happened in your experiment. Describe the interpretation of the results and their significance. Explain what the results mean, what conclusions can be drawn, etc. Do not put excessive focus on yield. You can simply mention your yield as low/high/moderate/reasonable and briefly discuss the possible reasons for that outcome. Your data should be presented in the form of tables and graphs as appropriate. All tables and graphs must be well-organized, numbered, and given clear descriptive titles. (e.g. Graph 1. Mp-Composition Diagram for Urea/Cinnamic Acid Mixtures.) Do not simply repeat your procedure and observations in this section. This is probably the most important section of your lab report. Deficiencies in this section will result in up to 30 points deduction from your lab report grade. 16. A good discussion of lab report writing can be found at http://www.professorkshow.com/sample-organic.html. If there is any contradiction to my instructions as above, follow my instructions. Page 3 How to calculate the yield of an organic reaction? Sample reaction: borohydride reduction of 2methylcyclohexanone. Make sure you have the balanced reaction written out: O OH CH3 3 + NaBH4 3 112.17 37.83 MW (g/mol) 114.18 The theoretical yield must be calculated based on the actual quantity of the starting materials you used. If the textbook mentions something like “The residue should weigh about 150 mg”, you cannot use that 150 mg as your theoretical weight of your product. According to the textbook instructions, you should use 300 mg of 2-methylcyclohexanone and 50 mg of sodium borohydride. Let’s suppose you get 0.2343 g of product in the end. Scenario 1: you indeed used exactly the quantities as indicated in the textbook. 2-methylcyclohexanone: 0.300 g ÷ (112.12 g/mol) = 0.00268 mol NaBH4: 0.050 g ÷ (37.83 g/mol) = 0.00132 mol Notice from the balanced reaction 0.00268 mol of 2methylcyclohexanone would consume 0.00089 mol of NaBH4. You actually used 0.00132 mol of NaBH4, so it is in excess and 2-methylcyclohexanone is the limiting reagent. The mole ratio between the products (a mixture of cis and trans isomers) and 2- methylcyclohexanone is 1:1, so the theoretical weight of the products is: 2-methylcyclohexanol: 0.00268 mol × (114.18 g/mol) = 0.301 g The actual yield you got is: (Notice the example calculation M on page 23 of the lab textbook contains one error. It should be 100% but not 100 in the equation.) Scenario 2: you actually used 0.303 g of 2-methylcyclohexanone and 0.034 g of NaBH4. 2-methylcyclohexanone: 0.303 g ÷ (112.12 g/mol) = 0.00270 mol NaBH4: 0.034 g ÷ (37.83 g/mol) = 0.00090 mol Notice from the balanced reaction 0.00090 mol of NaBH4 would consume exactly 0.00270 mol of 2-methylcyclohexanone. So both starting materials are the limiting reagent. If you choose to use NaBH4 as the limiting reagent, the ratio between the products to NaBH4 is 3:1, so the theoretical weight of the products is: 2methylcyclohexanol: 0.00090 mol × 3 × (114.18 g/mol) = 0.308 g (If you choose to use 2-methylcyclohexanone as the limiting reagent, the ratio between the products to 2-methylcyclohexanone is 3:3, or 1:1, so the theoretical weight of the products still is: 2-methylcyclohexanol: 0.00270 mol × (114.18 g/mol) = 0.308 g) Page 4 The actual yield you got is: Scenario 3: you actually used 0.303 g of 2-methylcyclohexanone and 0.030 g of NaBH4. 2-methylcyclohexanone: 0.303 g ÷ (112.12 g/mol) = 0.00270 mol NaBH4: 0.030 g ÷ (37.83 g/mol) = 0.00079 mol Notice from the balanced reaction 0.00079 mol of NaBH4 would consume 0.00237 mol of 2-methylcyclohexanone. You actually used 0.00270 mol of 2methylcyclohexanone, so it is in excess and NaBH4 is the limiting reagent. The ratio between the products to NaBH4 is 3:1, so the theoretical weight of the products is: 2-methylcyclohexanol: 0.00079 mol × 3 × (114.18 g/mol) = 0.271 g The actual yield you got is: 0.2343 g x 100% = 86% Your experiment will always fall into one of the above three scenarios when you run any two- component reactions. Make sure to show the calculation and reasoning process as above for your lab reports. Wrong yield calculation will result in 10 points deduction from your lab reports. 0.271 g Page 5 Chapter 41. Synthesis of Acetylsalicylic Acid (Aspirin) O O OH OH + H3C O C O O C H3PO4 CH3 ©Dr. Wang OH O C O CH3 + H3C O C OH  Roles of chemicals salicylic acid: reactant/starting material acetic anhydride: reactant & solvent 85% phosphoric acid: catalyst aspirin: desired product acetic acid: by-product  All the above chemicals are strongly acidic and corrosive. Be careful of their handling. Modified procedure: One person can prepare the water bath while your partner is weighing/getting the chemicals. A thermometer needs to be securely placed in the water bath, and the bath temperature could be in the range of 85 to 95 oC. Use the spirit thermometer if you have one. The bulb of thermometer could loosely touch the bottom of the beaker while the top of thermometer is held in place by a clamp. Use a smaller beaker (100 mL) with half full of tap water to generate the water bath. Note that the hot plate temperature setting needs to be higher than 95 oC. You could start from 200 oC and adjust it gradually to achieve ~90 oC water bath temperature.  When you weigh salicylic acid (a solid), any mass between 0.1350 to 0.1450 g is acceptable and you don’t have to get exactly 0.1380 g (or 138.0 mg). Make sure you don’t take too much out of the reagent bottle. Record the exact mass on your notebook and use it for yield calculation after the lab. If you get more salicylic acid than you need, throw it into the solid waste container. Do not put the excess back into the salicylic acid reagent bottle.  The amount of acetic anhydride does not need to be very accurate. (Discuss why in your lab report.) Mostly conveniently it can be measured in a small reaction tube more than half way toward the 0.5 mL mark. Because acetic anhydride is strongly corrosive and has a bad sour smell, the reagent bottle must be capped immediately after your measurement. To a reaction tube, add ~0.14 g of salicylic acid, a boiling chip, one drop of 85% phosphoric acid, and ~0.3 mL of acetic anhydride. Add the liquid acetic anhydride from the top of the reaction tube in a circular and slow motion to wash all solid down to the bottom of the tube. Mix the reactants thoroughly with a spatula and heat the reaction tube in the 90 oC water bath for 5 minutes. A transparent solution should form, however the boiling stone will apparently not dissolve. Take the reaction tube out of water bath, let it cool to room temperature, add ~0.5 mL of water, and thoroughly mix all liquids with a spatula. Water serves to destroy the unreacted acetic anhydride and provide a suitable solvent system for aspirin to crystallize out. Let the mixture sit at room temperature for 5 min and note the shape and color of the crystals. If crystallization of the product does not occur, scratch the liquid-air interface inside the tube with a 1 glass stirring rod until you begin to see the formation of tiny crystals. Further cool the tube in an ice/water bath for 10 min. Fit a filter paper in the Hirsh funnel, wet it with a few drops of water, and set up the vacuum filtration apparatus. The filter flask should be secured by a clamp to prevent the system from being tipped over. Using as much icy water as needed, transfer all solid inside the tube onto the wet filter paper. Use the spatula to pick up the boiling stone and rinse it with a few drops of icy water. Throw the boiling stone into the normal trash. Perform vacuum filtration and dump all the filtrate down the drain. With vacuum off, break big chunks of solid down to small pieces, and wet the crystals with 5 drops of ethanol using a Pasteur pipette. (Caution: if you use excessive ethanol you could lose all your product. Never directly squeeze the ethanol solvent bottle to get 5 drops.) Then turn the vacuum on for 5 min and let the wind constantly pass through the solid to remove all the residual liquid chemicals including acetic acid, water, and ethanol. The final product must appear loose and dry. Record its appearance including color and texture (white power, colorless needle-like crystals, etc.). Weigh the final product and submit it to Dr. Wang for IR analysis.  After IR analysis dispose of your aspirin product (excluding the weighing paper) into the solid waste container.  All your used glassware should be washed with soap water and then rinsed with small amount of acetone twice. Clean up all your bench area and hood. Fully close the hood sash all the way down before you leave.  Discussion of the reaction mechanism and side reactions can be skipped in your lab report. Compare the IR spectrum of your product to that of the starting salicylic acid and make conclusions on whether your reaction worked or not. Your IR spectrum of aspirin (solid alone) may be somewhat different from FIG. 41.1 on page 532 (solution in CHCl3) but should be reasonably close. Consult your Organic Chemistry lecture textbook and explain key characteristic peaks in your IR spectrum. Attach the product IR spectrum to your lab report.  Yield calculation is mandatory for all reactions. Consult the example included in “Lab Report Instructions” in Blackboard. As a reminder, you must calculate the mole amounts of all reactants (but not catalyst) and compare them to find out the limiting reactant. Because acetic anhydride is a liquid, you need to find its density using Internet. Note that mass = density x volume, and mole amount = mass ÷ molecular weight. 2 Acetylsalicylic Acid (Aspirin, Purpose: synthetise A cetylsalioylic Acid. caspirin) date 0 GOH o LOH control 요 4 roderi CH₃ Q=0 он + H3C co atz + CH₃ Ho Reference Williamson and saasters and masters , Macroscale and Microscale Organic Experiment page : ed. Table of Quantities o oc G/mol used on produced Subtance And wt Salicylic acidl 138.12 acetic anhydride 102.09 Mol Needed (from og.) Density mp bp Solutiting soluble in ether 1.4439/ml 188.6 200 colu benzene soluble 1,0828/cm² -73.1 137.8 Werter Miscible acetic acid 11049g/cm3 16-17 118 119 verter 60105 soluble 1145/cm3 B6 140 180.158 in warter aspirin. side reactions observation Procedure 1/24/2018 Prepare waiter berth, use a smaller beaker (room) with half full of tap the worker berth! water to generate b setrie weighing chemicals : Salicylic acid. 811350 - 0.1450 g. acetic anhydride small tube disul mark 7m{0 า 3 ab 20 os lock olt ord er the solvent went worbiel. transparent white floccule white floccule Come crystals of tube ou the wall of add ~0:14 Salicylic acid, a bolihing chip, one drop 85% tapau Nasonl acetic anhydride (from top of the tube in a cicular) heat for Smin in 90°c weiter bath. take out tube. let it cool. add noisml water mix thoroghtly sit for 5min in room temp (note sheipe and color of crystals) Cooling tube in Ice/nenter bath for lomin Fit a filter paper in Hirsh funnel. met it with water and set up the vacuum filtrertion apparatus transfer all solid inside the tube onto to pick up the boling stone and rinse se with icy water. Throw the stone in noranl trash Perform vacuum filitrertion and dump all the filtrate down the drain. with vacuum off, break big chunks of soild down to small pieces, and wel the cystals with 5 drops of ethanol using pasteur prpette Spatula white powder . spilled some product . Turn the racuum for 5 min. let Wind through solid, remove all chemicals. ( Record se appearance / color / texture.) & weish product and submit to Drway. 5 white powder 0.2950
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