#15 Synthesis of Ethyl Salicylate from Salicylic Acid

15 Synthesis of ethyl group Salicylate from Salicylic Acid ____________________________________________________________ _______________ Purpose Salicylic pane is converted to the tranquil ethyl salicylate by addition of ethanol. provides of salicylic sexually transmitted disease (week 1) and ethyl salicylate lead be found, as well as the general give out of the 2-step conversion of acetyl salicylic acrimonious to ethyl salicylate. Introduction Esters ar organise from the reaction of acids and alcohols O O R-C-OH + HO-R R-C-OR + H2O cid alcohol ester water The beautiful smelling oil of ethyl salicylate is do by reacting salicylic acid (week 1) with bare(a) ethanol. An acid atom smasher is also needed. salicylic acid (SA) ethanol ethyl salicylate (ES) The boilers suit generate is determined from multiplying yields of the two reactions 1. ASA + HCl(aq) SA and 2. SA + ethanol ES + water utensil The reaction takes place by refluxing (gentle boiling) in a cytosine-mL round roll in the hay flask. This time the ice-cooled condenser is essential, otherwise the ethanol reactant (b. . 79? C) would evaporate beforehand the reaction was over. melt down points of acetyl salicylic acid and salicylic acid (dried from week 1) are taken with MelTemp devices. If you have never used one your instructor will demonstrate. MelTemp C OH O OH H OC H2CH3 H + C OH O + OCH2CH3 + H2O2 surgical operation art object A Esterification of Salicylic Acid with Ethanol 1. Before starting back away a spatulaful (that will be 0. 1 g) of SA (salicylic acid) and place in a labeled plastic vial to use for melting points. 2. In a 100 mL round bottom flask, mix at least(prenominal) 5 g alter salicylic acid (0. 43 groyne) with 20 mL 100% ethanol. The salicylic acid should be weighed out to two decimal places and put down on the information sheet. The alcohol is in excess. It base be poured from a graduated cylinder, and should not be scaled down. tint Use more salicyl ic acid if you have more from the first week. You should have between 7 and 8 g. Ad vindicatory amount of ethanol accordingly, say to 30 mL. 3. supplement most 1/2 gram of boric acid catalyst that we use as a substitute for concentrated sulfuric acid in this particular esterification. 4. Place entire assembly on a hot plate and heat until the alcohol is boiling.A setting of approximately 3 on the hot plate underside be tried and true and then adjusted up or down as needed. You may need to add more ice. Note While the refluxing is taking place, you can work on break out B, in which the materials you have already made are characterized by taking their melting points. 5. Reflux for a stripped-down of 1 hour and 30 minutes or longer as time allows. Cool until the flask is no longer hot, then in an ice bath, until the mixture is at room temperature. Transfer to a salvage separatory funnel. 6. Add 10 mL 2M NaOH(aq) . The mixture turns milky as approximately 2-3 mL of ester appea rs at once as an insoluble bottom spirit level.Ethyl salicylate is an oily liquid with a density of 1. 1 g/mL. stop a few minutes until the cloudy emulsion begins to clear up. You can estimate the yield by ending the funnel and measuring an fit volume of water. Record this. You will probably give about(predicate) 1/2 mL for every 1 gram of salicylic acid. 7. You should be suitable to recover about 1. 5 mL of the ester oil by separating the layers development a separatory funnel. Allow the bottom layer to pour into a vial. This layer contains mostly ethyl salicylate and should have a very pleasant odor, something uniform wintergreen.It will also include a little NaOH solution and then will not be clear and sparkling. If you have enough liquid you can attempt the next step. 8. Dry by mixing with a small amount of anhydrous magnesium sulfate. See your instructor to get help with this. Pour off the clear ethyl salicylate. 3 Part B Melting Points 1. Measure melting points of t he dry acetyl salicylic acid and the salicylic acid using the small samples reserved for this purpose. Record on data sheet and compare with literature values. Part C Yields 1. The 50 acetylsalicylic acid tablets contained 16. 25 g ASA.To estimate yields in your next 2 reactions, apply the wet ASA you used contained 12 g ASA. Then from the mass of dry salicylic acid obtained fix the yield of salicylic acid. 2. Convert the volume of ethyl salycilate to grams using the density, 1. 1 g/mL. Record. Estimate yield of ethyl salicylate from salicylic acid and record, retaining just 2 significant figures. 3. Find the overall yield of the two-step run Step 1 acetyl salicylic acid (ASA) to salicylic acid (SA) Step 2 Salicylic acid (SA) to ethyl salicylate (ES)4 Data and Results (yield of ethyl salicylate)Name(s) ____________________________________________________________ ____ Part B Melting Points Compound Measured Melting Point (? C) Literature shelter (? C) Acetyl Salicylic Acid 134 135 Salicylic Acid 158 160 Yields Assuming ASA (from stock of 50 aspirin tablets) = 12 g SA (from hydrolysis of ASA) ______ g Reactant SA esterified ______ (usually most of the amount above) grating volume of ethyl salicylate _______ mL (density ES = 1. 1 g/mL) potful ethyl salicylate ________g Maximum g SA Maximum g ES go in amounts where indicated in the table below and find the yields. Reaction Reactant Product potReactant (g) band Product (g) Maximum Mass Product (g) Actual Yield % ( 2 sig. figures) ASA SA 12 g ASA* g SA g SA SA ES g SA g ES g ES *Assuming 75% declension yeild. Overall Yield for 2 locomote (product of 2 yields above) Questions 1. Recalculate the overall yield for a three-step process including the 75% extraction. 2. The synthetic thinking of a parvenue drug may require as many another(prenominal) as 30 steps, some of which produce much less than 90% yields. Comment on this (without doing any calculations). ________________________________________ ____________________ _______________5 instructors GuideEthyl Salicylate Part B Melting Points Compound Measured Melting Point (? C) Literature Value (? C) Acetyl Salicylic Acid 134 134 135 Salicylic Acid 159 158 160 Yields Assuming ASA (from extraction of 50 aspirin tablets) = 12 g SA (from hydrolysis of ASA) 7. 3 g Reactant SA esterified 7. 0 g (usually most of the amount above) Approximate volume of ethyl salicylate 3. 0 mL (density ES = 1. 1 g/mL) Mass ethyl salicylate 3. 3 g Maximum g SA 10 g ASA x 1 bulwark ASA x 1 mol SA x 138 g SA = 9. 2 g SA 180 g ASA 1 mol ASA 1 mol SA Maximum g ES 7. g SA x 1 mol SA x 1 mol ES x 166 g ES = 8. 4 g ES 138 g SA 1 mol SA 1 mol ES Enter amounts where indicated in the table below and find the yields. Reaction Reactant Product Mass Reactant (g) Mass Product (g) Maximum Mass Product (g) Actual Yield % ( 2 sig. figures) ASA SA 12 g ASA* 9. 2 g SA 7. 3 g SA 79% SA ES 7. 0 g SA 8. 4 g ES 3. 3 g ES 39% *Assuming 75% extraction yeild. Overall Yie ld for 2 steps (product of 2 yields above) 0. 79 x 0. 39 x 100 = 31% Questions 1.Recalculate the overall yield for a three-step process including the 75% extraction. 2. The synthesis of a new drug may require as many as 30 steps, some of which produce much less than 90% yields. Comment on this (without doing any calculations). ____________________________________________________________ _______________ 1. Overall yield = 0. 75 x 0. 79 x 0. 39 x 100 = 23% 2. The yield would be very very small, making this an expensive process. 6 Instructors Guide Ethyl Salicylate(contd) Time maximum Equipment and Materials per group Items fleck Comment stir/hot plates 1 stir bars 1 00-mL round bottom flasks 1 Weighing papers 1 family per signifier Ice 50-mL graduates 1 Top loading balance 2 per class With power supply MelTemps 2 per class thermometer 2 per class For Meltemp m. p. tubes (closed) 50 per class 250-mL beakers 1 for water heating bath Microscale ice-skating rink clamp 1 (yellow) ice-c ooled condensers 1 dance orchestra stand 1 Ring stand clamp 1 separatory funnels 1 boric acid 5 g per class antifungal agent spoon spatulas 1 100% ethanol 1 L per class 2 M NaOH 50 mL magnesium sulfate 10 g per class Epsom salts sentry go glasses 1 per student Rubber gloves 1 box per class7 Ideas/ selective informationWe make ethyl rather than methyl salicylate, because methanol is toxic. Under Part A. 3. Note This experiment was designed to be done using folk chemicals. Although Science in Motion can provide concentrated sulfuric acid, we have decided that it is too dangerous to handle. Under Part C. 1. Note Repeated extractions were done in our lab. They all gave about 75% yields and about 12 g dry ASA. 2M NaOH solution could be prepared by adding solid NaOH to a volumetric flask and then diluting with distilled water to the mark on the flask. Molarity mol/L g NaOH for 1 L solution g NaOH 500 mL solution 2 80 40