-207010-74295Organic your mark. **Please note that:Lab reports submitted
-207010-74295Organic chemistry 1Laboratory report FOR EXPERIMENT 4PROFESSOR: shalini vijharleen kaur 991488347 harkirat singhStudent Name Student ID Lab PartnerSection: Thursday 8 AM – 10 AM ?Thursday 10 AM–12 PM ?Thursday 12 PM – 2 PM?LAB TITLE: caffeine extractiondATE PERFORMED 11 October 2018 dUE DATE 1 November 2018DATE SUBMITTED (by professor) LATE PENALTY Organic Laboratory Report EvaluationCOMPONENT POINTSA: Report template out of 70 /70B: Using outside resources, appropriate referencing, ACS formatting, citation in the text, list of references /4C: Overall organization of report (complete and type the cover sheet, print single sided, keep questions and answers on the same page, keep each table together on the same page; remove/add extra spaces wherever required, attach the raw data to the back of the report, …) formatting*, clarity of comments, spelling and grammar, correct number of significant figures, units, attention to details, correct use of ChemDraw software for structures /10D: Punctuality, time management, preparedness, performance (observed during the lab period) /6E: Photocopy of the original results** (recorded organized and detailed observation and required data) /10F: Late penalty (10% per day) Total (A+B+C+D+E-F) *Please note that any changes in the formatting and/or content (including but not limited to the mark allocations) of the report template are strongly prohibited and will affect your mark. **Please note that:Lab reports submitted without the signed original results will not be marked and will receive a grade of zero. All pages of the notebook require to clearly showing the page number, name of the student, date, signature of the instructor and date stamp.
Copy of the pages which doesn’t have any of the above, will NOT be accepted.Copies must be legible, clearly show all the data and observations in addition to the above information (no cut off).Copies must be attached in order of increasing the page number at the back of the report.A new signature and date stamp is required for all the accomplished work other than the lab period.A soft copy of the lab report must be submitted to Assignments folder on Slate in a .doc or .
docx format before the report is due (including pictures of notebook pages). Reports submitted without a soft copy will NOT be marked.Name : Harleen kaur Partner’s name : Harkirat SinghLab Section : 1189-56166 Date : 27 october 2018REPORT TEMPLATE (Mark = /40)EXPERIMENT 4CAFFEINE EXTRACTIONData and Observation (provide appropriate unit and significant figures wherever required)Melting point range of the pure caffeine Trial 1= 235.6-242.9°C (1 mark)Melting point range of the pure caffeine Trial 2= 235.4-237.
8°C (1 mark)Appearance of the pure caffeine = bitter white crystalline appearance (1 mark)Literature value for melting point range = 235-237°C (1 mark)Appearance of the extraction in the beaker after heating = dark blackish color appeared (1 mark)Appearance of the aqueous layer in separatory funnel = dark black color liquid (1 mark)Appearance of the organic layer before addition of Na?2SO4 ?(before drying) = some of the droplets (yellow colored) that came from the aqueous layer were observed floating on organic layer. (1 mark)Appearance of the organic layer after drying = clear liquid obtained which means there were no droplets observed floating on the top that could be a part of the aqueous layer (1 mark)The caffeine content according to the nutrition label on the tea box = 34 mg/175 mL (1 mark)Total mass of tea bags = 17.27 g (~3.71g each) (1 mark)Mass of 5 empty tea bags ? 0.65g (i.e.
0.13g each X 5) (1 mark)Total mass of tea without bags = 16.62 g (1 mark)Calculate % (w/v) of caffeine in a 250 mL tea cup which was brewed with the 5 tea bags you used in the lab. Show your calculations. Assume % (w/w) of caffeine in dry tea is 3 %. (4 marks)=total Mass of tea without tea bags = 16.62gVolume = 250 mL3% w/w of caffeine in dry tea means 3g of caffeine in 100g dry tea,In 16.
62g of dry tea, mass of caffeine = 3g100g×16.62g=0.4986g% w/v of caffeine =0.4986g250mL×100=0.
20%Postlab Questions (24 marks):What is the role of NaOH in this experiment? (4 marks)ANS. The organic layer obtained during the caffeine extraction experiment contained some impurities. Therefore in order to remove the water soluble impurities from the organic layer, the solution is washed with 50% NaOH. Also the water does not only contain the caffeine but tannins and some other compounds as well, which are also soluble in the organic layer.
Hence the NaOH reacts with the tannic acid to form insoluble salts which then settles down as precipitate and we are left with pure caffeine. One of the reason to use the basic solution is that the -OH group also provides more affinity for the dichloromethane to react.1Why was Na2SO4 added? (1 mark)ANS. Anhydrous Na2SO4 is used as a drying agent in order to remove the excess water until no clumps are observed (as it has high affinity for water) and we are just left with pure caffeine.2Is dichloromethane a good solvent for this experiment? Explain your answer.
(3 marks)ANS. yes dichloromethane is a good solvent for the extraction of caffeine during the experiment as the caffeine is more soluble in the dichloromethane than in the water. It does not react with the components found in the dichloromethane-caffeine mixture, has lower boiling point, dissolves caffeine at room temperature and is evaporated at the end leaving behind pure caffeine. Also it is more denser than water, hence caffeine is more soluble in dichloromethane than water.3Why is it necessary to vent (open the separatory funnel) during a liquid-liquid extraction? (2 marks)ANS. When the mixture in the separatory funnel is shaken and the funnel is inverted and swirled during a liquid-liquid extraction, pressure is generated due to establishment of rapid equilibrium and increasing the surface area in contact among the two liquids in the separatory funnel. Hence the separatory funnel is vented to release that pressure and avoid excess bumping of the liquids.
4What are the compounds left behind in aqueous layer in liquid-liquid separation? (3 marks)ANS. Because of the addition of NaOH to the mixture during the caffeine extraction, OH- was dissociated into the aqueous layer. Also it converted the Tannins into insoluble salt, hence, we can find insoluble salts of tannins, chlorophylls and some flavonoid pigments in the aqueous layer. Because caffeine was more soluble in dichloromethane, it was settled at the bottom of the separatory funnel into the organic layer. Therefore caffeine is not found in the aqueous layer in liquid-liquid separation.
5Why is it necessary to cool the mixture to room temperature before transferring it to the separatory funnel and adding dichloromethane? (2 marks)ANS. It is important to cool down the mixture at room temperature before the addition of dichloromethane because the dichloromethane has a low boiling point (about 40°C). If the mixture was still hot, the dichloromethane may have evaporated and we could have error in the final result in obtaining pure caffeine during the extraction process. But cooling the mixture to room temperature allows the dichloromethane to react efficiently and form two layers (aqueous and organic) in the separatory funnel.
6Express the density (specific gravity) of dichloromethane in g/mL and identify if it is the top layer or bottom layer in the separatory funnel. (2 marks)ANS. the density of dichloromethane is noted to be 1.325 g/mL, however the density of water is noted to be 1.
000 g/mL at room temperature. Clearly, it can be observed that the dichloromethane has more density as compared to the water and being more denser and heavier, it forms the bottom organic layer in the separatory funnel.7Is caffeine more miscible in organic layer (dichloromethane) or aqueous layer? Why? (3 marks)ANS. As we know, dichloromethane (CH2Cl2) is a hydrocarbon. The electron density in its structure is bent towards the chlorines present in it. If we look at caffeine, it has a planar structure.
No matter caffeine is water soluble, but it is more soluble in dichloromethane (organic layer) because of its polarity to interact (mostly with the carbonyl oxygens). Hence we can call it as a polar hydrocarbon because a large plane in its structure is observed to be a hydrocarbon.8Structure of CaffeineAssume you have a mixture of caffeine and phenol, using what you learned from this lab, draw a flowchart to separate the two compounds. Use ChemDraw, to draw all structures.
(4 mark)ANS. flowchart for separation of caffeine from mixture of caffeine and phenol 9 Bibliography (reported in ACS format):Chameketa.edu; Caffeine Extraction pdfhttp://faculty.chemeketa.edu/jcammack/CH241-3B%20Lab/CH241B%20Labs/CH241%206%20Caffeine%20Extraction%20F14.pdf (accessed on 30 October 2018)Edspace; American.edu; pdfhttps://edspace.american.edu/ap7794a/wp-content/uploads/sites/159/2015/03/Isolation-of-Caffeine-from-Tea-Leaves-via-Acid-Base-Liquid-Liquid-Extraction.pdf (accessed on 30 October 2018)Edspace; American.edu; pdfhttps://edspace.american.edu/ap7794a/wp-content/uploads/sites/159/2015/03/Isolation-of-Caffeine-from-Tea-Leaves-via-Acid-Base-Liquid-Liquid-Extraction.pdf (accessed on 30 October 2018)http://web.uvic.ca/~berryde/techniques/sep%20funnel.pdf (accessed on 30 October 2018)Sheridan Faculty of Applied Science & Technology; Organic chemistry 1; Lab manual; experiment #4; Caffeine Extraction https://slate.sheridancollege.ca/d2l/le/content/527556/viewContent/7066629/View?ou=527556 (accessed on 30 October 2018)https://www.coursehero.com/file/p26npf3/For-example-if-the-tea-was-not-cooled-enough-before-adding-the-dichloromethane/ (accessed on 29 October 2018)Courses; Chem.psu.edu; Experiments pdfhttp://courses.chem.psu.edu/chem36/Experiments/PDF’s_for_techniques/Liquid_Liquid.pdf (accessed on 30 October 2018)Chemhelp; Reddit; caffeine extraction commentshttps://www.reddit.com/r/chemhelp/comments/3kxvtw/why_is_caffeine_more_soluble_in_dichloromethane/ (accessed on 29 October 2018)Coursehero; flow diagramhttps://www.coursehero.com/file/p2nfajc/Flow-diagram-for-the-separation-of-caffeine-from-tea-leaves-Tea-Leaves/ (accessed on 30 October 2018)