University of California Nucleophilic Substitution Reaction Experiment Lab Report

Science

University Of California Los Angeles

Question Description

I need someone to answer the questions listed within the Report Scaffold PDF. All instructions are within the pdf and Ive attached both the data set and lab procedures/objective in another pdf.

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APPLICATION OF A SUBSTITUTION REACTION: PART 1 REACTIONS:​ Acid-Base, Nucleophilic Substitution TECHNIQUES:​ reflux conditions, melting point This is the first part of a two-part experiment in which you will learn several techniques used regularly in the organic chemistry laboratory. You will react one of three unknown compounds with benzyl bromide in the presence of sodium hydroxide to synthesize a benzyl ether product. In the next lab period you will purify and identify your product. Is the main mechanism in operation more likely to be S​N​1 or S​N​2? PRE-LAB ASSIGNMENT: Complete all portions of pre-lab ELN work according to guidelines Check that SDS files for all reagents are present in your SDS Files folder. Add files for any missing compounds. Rewrite the procedure in your own words! Complete Video Quizz(es) on Canvas Sapling assignment IMPORTANT SAFETY INFORMATION Sodium hydroxide (NaOH) is caustic and toxic. Wear gloves, work in the fume hood, and wash immediately if it comes into contact with bare skin. Benzyl bromide is a lachrymator and is irritating to skin and mucous membranes. Do not breathe vapors. Wear gloves and do all work in the hood. 4-Methoxyphenol is toxic when ingested and an irritant to the skin and mucous membranes. Do not breathe vapors. Wear gloves and do all work in the hood. 4-Chlorophenol ​is toxic when ingested and an irritant to the skin and mucous membranes. Do not breathe vapors. Wear gloves and do all work in the hood. 4-​tert​-butylphenol is toxic when ingested and an irritant to the skin and mucous membranes. Do not breathe vapors. Wear gloves and do all work in the hood. Ethanol is flammable. Inhalation of vapors can be toxic. Work in the fume hood and keep away from sparks or flames. EXPERIMENTAL PROCEDURE: Place a stir bar and 0.280 g of sodium hydroxide into a 25-mL round-bottomed flask. Add 10.0 mL of your assigned unknown nucleophile solution (0.35 M in ethanol). Attach your condenser and heat at reflux in an aluminum heating block with sand for at least 15 minutes after all of the sodium hydroxide dissolves. ​What does “reflux” mean? A color change might occur during this time period. After the reflux period, allow your reaction mixture to cool to room temperature. Add 0.55 mL benzyl bromide to the round-bottomed flask through the condenser. Using a disposable pipette, rinse the inside of your condenser with ~0.5 mL ethanol to wash any residual benzyl bromide on the inside of the condenser into the reaction flask. Reflux the reaction mixture for at least one hour. While waiting, chill 50 mL deionized water (DI water) in an ice bath. After the one hour of refluxing is complete, allow the reaction mixture to cool until it can be handled without burning your hand and then slowly pour the mixture into a 50 mL beaker that is approximately ½ full of ice. Use no more than half of the water you have been keeping chilled to rinse the round-bottomed flask. Pour the rinse into the beaker and swirl the beaker until all of the ice melts. Vacuum filter your solid product using a Büchner funnel. Rinse the product twice with your remaining ice-cold DI water and allow the solid to dry by using the vacuum to pull air through the sample in the filter funnel for at least 15 minutes. ​Why is it important that the DI water you use to rinse is ice-cold? Save ~1-2 mL of your filtrate for analysis in the following lab period. Transfer the filtrate sample to the vial provided, label it, and turn it in to your TA. ​What is important information to include on a label? Once your product is dry, take a melting point. When you are finished with all work for the day, transfer all of your product to a vial. Label the vial and give it to your TA. DATA For this first experiment the data you need to record will be listed here. As we progress through the class, less detail will be provided. You should always be thinking about what data are needed. A good rule to remember is that it’s better to have data and not need them than to need data and not have them. For your in-lab assignment, you will record and use data provided in the experiment videos. Make sure you adjust any sections in your notebook accordingly to match unknown compounds used in experiment videos, including general reaction, mechanism, GHS tables, and calculations. Think of experiment videos as your time in lab. For this lab period you should record: The actual amounts of all reagents used if they vary from the planned amounts. Any observations during your experiment. Mass of product obtained. (This is your “crude” or “unpurified” yield.) Observations about the physical state and appearance of the product. Melting point of crude product. POST-LAB REPORT We will start out using a lab report scaffold to learn how to write scientific reports. You can start working on the Nucleophilic Substitution Scaffold Worksheet for Experiment 2. This worksheet is posted on Canvas. It will not be due until after you complete the second part of Experiment 2. Be sure to read and follow the instructions provided on the worksheet! For your post-lab assignment, you will use and present the data provided to you by the data quiz on Canvas. This data will be different to that recorded from experiment videos and used for your in-lab assignment. Chem 51LB Substitution Reaction Part 2 Purification and Characterization of Substitution Product REACTIONS:​ None TECHNIQUES:​ recrystallization, melting point, thin layer chromatography This is the second part of a two-part experiment. Previously, you reacted one of three possible nucleophiles with benzyl bromide in the presence of sodium hydroxide to produce a solid product. In this lab period you will purify the product using recrystallization and identify it and, therefore, your unknown nucleophile via melting point and thin layer chromatography (TLC). Additionally, you will analyze the saved aliquot of your filtrate for the presence of reactants, product, or products of side 1​ reactions. A ​ H NMR spectrum of your product will be provided after the lab period. PRE-LAB ASSIGNMENT: Complete all portions of pre-lab notebook work according to guidelines Check that SDS files for all reagents are present in your SDS Files folder. Add files for any missing compounds. Rewrite the procedure in your own words! Complete Video Quizz(es) on Canvas Sapling assignment IMPORTANT SAFETY INFORMATION Ethanol ​and ​ethyl acetate​ are volatile, toxic and flammable. Use in the fume hood. Hexanes​ is volatile, flammable, and a neurotoxin. Avoid contact with skin and eyes. Use in fume hood only. Avoid breathing fumes. INFORMATION ABOUT STANDARDS TLC Standard Key A 4-chlorophenol B 4-methoxyphenol C 4-tert-butylphenol D 4-chloro phenyl benzyl ether E 4-methoxy phenyl benzyl ether F 4-tert-butylphenyl benzyl ether G Benzyl bromide H Benzyl alcohol Melting Pt. of Standards D 70 °C 4-chloro phenyl benzyl ether E 71 °C 4-methoxy phenyl benzyl ether F 64 °C 4-tert-butylphenyl benzyl ether EXPERIMENTAL PROCEDURE: Immediately set aside ~20 mg of your crude product for later. Recrystallization: Heat approximately 20 mL of ethanol and 20 mL of water in separate flasks or beakers, but on the same hot plate. Adjust the temperature of the hot plate so that the ethanol is hot but not boiling. Recrystallize your crude product from ethanol/water by placing your product into an appropriately sized Erlenmeyer flask and slowly adding portions of the hot ethanol just until the solid is completely dissolved. You will need to stir or swirl the flask containing your product solution and keep it warm during this process. ​Why is it important to keep the solution warm? Be careful not to add too much solvent! ​What will happen if you add too much solvent? What can you do if you add too much solvent? Add water dropwise and swirl your recrystallization flask just until a slight cloudiness persists. ​What does the cloudiness being present mean? Add hot ethanol again dropwise until the cloudiness disappears. ​Why does the cloudiness disappear? Allow the solution to cool to room temperature and then place the flask into an ice bath to complete recrystallization. ​Why don’t we just put the solution directly into the ice bath without cooling to room temperature first? Cool a small beaker of water in ice while you wait for crystallization to occur. (Note that this is the general procedure for recrystallizing from mixed solvent when the exact solvent ratios needed are not known. You will be expected to remember this general procedure in the future.) Vacuum filter the solid and rinse with ice-cold water. ​Why is it important to rinse the crystals? Why is it important that the water is ice-cold? Allow the solid to dry in the filter funnel while pulling air through the sample for at least 15 minutes. Record the mass of the dried product. Melting Point: Obtain a melting range for the recrystallized product and your crude product you set aside earlier (if you did not do so in the previous lab period or if the previous crude melting point was very low). ​Why are we interested in the melting point of both crude and recrystallized solid? Perform mixed melting point experiments using your pure product with the standards provided to confirm the identity of what you isolated. What does a mixed melting point experiment tell us? If the melting range of your recrystallized product is low, try drying it again for a longer period of time. TLC (Product): Make a TLC sample of your recrystallized solid by adding ~10 mg of solid to a small beaker, flask or test tube and dissolving the solid in ~1 mL of acetone or ethyl acetate. Use this sample to compare your product to the TLC standards provided, and the crude product you set aside before recrystallization. This will help to confirm the identity of your product. To help you understand TLC, you will run TLC plates of your product in three different eluting solvents: hexanes, 9:1 hexanes/ethyl acetate, and 1:1 hexanes/ethyl acetate. You will need to mix the eluting solvents yourself. Make 10 mL of each solvent mixture. How will you make the eluting solvent mixtures? ​Which solvent system is most polar? Least polar? Follow the general procedure outlined in your Techniques book for spotting, developing, and visualizing TLC plates. Note that your solid does not have to be completely dry for a TLC sample. If you found that your melting point of your recrystallized solid was low and decided to dry it again, take out enough to make a TLC sample and move forward with this portion of the experiment while the remaining solid is drying. TLC (Filtrate): **May be done at any point during lab period. Use your time wisely!** Remember that mass is neither created nor destroyed, so any reactants not converted to product, any product that stayed in solution, and any other products formed will be present in your filtrate. Use TLC to analyze your filtrate for the presence of these compounds. Compare to your crude product as well. Standard TLC solutions will be provided for: all three possible nucleophiles, all three possible benzyl ether products, benzyl bromide, and benzyl alcohol. Elute your TLC plates with a 9:1 hexanes/ethyl acetate solution. Product Collection: Any product remaining after your analyses are complete will be collected. Place the remaining product in a vial and label the vial with the following information. Names of all students in your group Unknown # Structure of product Melting range of recrystallized product Give the labeled vial containing product to your TA. Unused portions of your filtrate aliquot should be poured into the appropriate waste container. DATA ANALYSIS​: Before you leave the lab for the day, use the data you collect to Determine the identity of your product. Determine the identity of your unknown nucleophile. Identify the contents of the filtrate to determine whether any additional substitution products formed. Identify the effect of eluting solvent mixture polarity on TLC. Identify which of the three eluting solvents for TLC was the best for your product. Before you leave the lab for the day, use the results of your data analysis to identify other students with the same unknown as yours and compare results. 1​ After the lab period, your TA will combine like products and take a ​ H NMR spectrum of this combined sample. You will receive your spectrum later in the week. Use this spectrum provided by your TA to confirm the identity of your product. For your in-lab assignment, you will record and use data provided in the experiment videos. Make sure you adjust any sections in your notebook accordingly to match unknown compounds used in experiment videos, including general reaction, mechanism, GHS tables, and calculations. Think of experiment videos as your time in lab. 51LB: Nucleophilic Substitution Unknown #1 Part 2 Chemical Amount Mass of Vial 16.101 g Mass of Vial and Recrystallized Product 16.641 g Melting Point Data Compound/Mixture Melting Point (℃) Crude Product 64.5 - 71.0 Recrystallized Product 70.3 - 72.6 Recrystallized Product and 4-chlorophenyl benzyl ether 70.3 - 73.0 Recrystallized Product and 4-methoxyphenyl benzyl ether 56.5 - 69.2 Recrystallized Product and 4-tert-butylphenyl benzyl ether 57.8 - 70.0 TLC Data Solvent System 9:1 hexane/ethyl acetate TLC Plate Solvent Front (cm) 3.0 Recrystallized Product, “R,” Left Lane (cm) 1.6 Crude Product, “C,” Right Lane (cm) 1.8 Solvent System 100% hexanes 51LB: Nucleophilic Substitution TLC Plate Solvent Front (cm) 3.3 Recrystallized Product, “R,” Left Lane (cm) 2.4 Crude Product, “C,” Right Lane (cm) 2.2 Solvent System 1:1 hexane/ethyl acetate TLC Plate Solvent Front, Left Lane (cm) 3.4 Recrystallized Product, “R,” Left Lane (cm) 2.5 Solvent Front, Right Lane (cm) 3.5 Crude Product, “C,” Right Lane (cm) 2.35 Solvent System 9:1 hexane/ethyl acetate 51LB: Nucleophilic Substitution TLC Plate Solvent Front (cm) 3.5 Filtrate, “F” (cm) 0.35 4-chlorophenol, “A” (cm) 0.14 4-methoxyphenol, “B” (cm) 0.11 4-tert-butylphenol, “C” (cm) 0.17 Crude Product, “C​p​” (cm) 1.8 Solvent System 9:1 hexane/ethyl acetate TLC Plate Solvent Front (cm) 3.1 Recrystallized Product, “R​p​" (cm) 1.5 4-chlorophenyl benzyl ether, “D” (cm) 1.5 4-methoxyphenyl benzyl ether, “E” (cm) 1.1 4-tert-butylphenyl benzyl ether, “F” (cm) 2.0 l 0 I a "� � � I' :si "" " - II 320 - 300 -� I -280 - 260 ..,, r--i - - 240 - - 220 f- - 200 f- - 180 J � + + + + - I -f- f- . n . 160 - 140 -f- - 120 - 100 I + -80 60 I 40 ' .. ' L0.0 9.5 ' 9.0 ' 8.5 8.0 J I . 7.5 - 1" I � ' 7.0 � 20 .,...." I 6.5 . 6.0 ' 5.5 5.0 fl (ppm) =i � 4.5 ' 4.0 . 3.5 3.0 ' 2.5 ' 2.0 � 1.5 0 . 1.0 --20 ' 0.5 0.0 READ THESE INSTRUCTIONS FIRST Instructions​: Report scaffolds are provided to help you learn how to write about the experiments you conduct. We will start by providing general questions for each section and examples of specific questions connected to the current experiment. For this assignment, answer the ​specific questions provided using complete sentences in the third person passive voice, but keep the general questions in mind. As we move through the quarter the report scaffolds will provide less and less support by removing the specific questions and then not providing a scaffold at all! Each question in this scaffold is numbered. In a separate document, number your responses to the ​Experiment-Specific Questions only. Do not write the specific questions in your separate document as these will only take up the space you need for your responses to those questions. Also, do not include the general questions. The document containing your responses should not exceed a total of five pages. Mechanism drawings may be attached at the end of your document (in the appendix) and do not count toward the five page limit. Unless the rubric specifies otherwise, all responses should be included in the body of your report submission and count toward the page limit. This includes results tables. Check the rubric for the assignment that tells you what to include. All other materials (i.e. mechanisms, calculations, images) may go in the appendix and do not count toward the page limit. Post-Lab Report Format: MUST BE TYPED IN WORD OR A SIMILAR PROGRAM, NOT AN ELN PAGE! Times New Roman; 12 pt. font; double spaced; 1” margins; no rd more than 5 pages; use 3​ person passive voice only (​For example, “We dissolved the white solid in 10 mL of hot water,” should be written as, “The white solid was dissolved in 10 mL of hot water.”​). Include your name, student ID number, and lab course code. This format is ​NOT OPTIONAL and TAs will return work as unsatisfactory if the format is not followed. Purpose/Introduction General Questions: What were we trying to accomplish with this experiment? How did we plan to accomplish this? The purpose of an experiment is not simply to introduce a student to a technique or reaction! Experiment-Specific Questions (answer these)​: 1. What reaction was conducted in this experiment? What reagents were used? How was the reaction set up? Don’t provide too much detail here! You should answer this question in 1-2 sentences! 2. Did you know the exact reagents you were using or was there an unknown involved? If an unknown was involved, the purpose should include determining what that unknown compound was! Mention all possible unknowns. Again, this can be answered in one sentence! You might be able to combine this sentence with the one above! 3. What techniques were used to purify and identify the product(s) of the reaction? Don’t go into detail here. Just list each and its purpose in a sentence. Theory General Questions: Assume you are writing for another student who has taken organic chemistry before but might have forgotten some of the details of reactions and lab techniques. What information about the reaction and techniques being used in this experiment would you need to remind them of to make sure they understand what you did, why you did it, and what the results mean? Experiment-Specific Questions (answer these): 4. What two types of reactions happen in this experiment? What components does each reaction have? What are the important factors of nucleophilic substitution reactions? You should include some depth for aspects relevant to this particular experiment, but you don’t need to go into much depth for factors that are not directly related. 5. How is melting point being used in this experiment? Why are we using it? What would someone need to know about how melting point works to understand how and why it is being used and to understand the data and results? Don’t include any results here. You are providing the proper background for the reader to be able to interpret your results later. 6. How is recrystallization being used in this experiment? Why are we using it? What would someone need to know about how recrystallization works to understand how and why it is being used and to understand the data and results? 7. How is thin layer chromatography (TLC) being used in this experiment? Why are we using it? What would someone need to know about how thin layer chromatography works to understand how and why it is being used and to understand the data and results? 8. How is nuclear magnetic resonance (NMR) being used in this experiment? Why are we using it? What information do chemical shift, splitting, and integration provide that would help someone determine a chemical’s identity? Keep this to no more than 3 sentences. Results For your post-lab assignment, you will use and present the data provided to you by the da ...
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