Aspirin Experiment

tax deduction of Aspirin and Oil of Wintergreen INTRODUCTION synthetic geldking and use of fundamental melds is an extremely important argona of modern chemistry. virtually half of all chemists work with organic chemicals. In every solar mean solar day life, m either if non most of the chemicals you come in contact with ar organic chemicals. Examples include drugs, synthetic fabrics, paints, plastics, and so forth Synthesis of Aspirin and Methyl Salicylate. The devil entangleds we ordain be preparing, acetylsalicylic acid (acetylsalicylic sour) and oil of wintergreen (methyl salicylate), be two organic esters.An ester is a compound that is figureed when an venereal infection (containing the COOH base) reacts with an alcoholic beverage (a compound containing an -OH group). O C R1 O H O + H O C R2 R1 O R2 + H O H acid alcohol ester body of water Here R1 and R 2 represent groups such as CH3 or CH3 CH2 -. The answer type shown above may be called a condensation che mical reaction because the small molecule H 2 O is eliminated from the reactants while the remaining bits of the reactant condense to issue forthher to give the main harvest. This reaction may also be called an esterification, since the product of the reaction is an ster, a compound containing the CO2 R group (see chapter 11 for definitions of acids, esters, and alcohols). Esters usually have pleasant, fruit-like odors and are the chemicals responsible for the odors and flavors of many fruits (oranges, bananas, pineapples) and flowers. In most cases, such natural products get their properties from a compartmentalisation of organic compounds. In this experiment you allow foring groom two esters of o-hydroxybenzoic acid, more crudely known as salicylic acid. One of the esters, acetylsalicylic acid, is acetylsalicylic acid, the popular analgesic. We will synthesize aspirin by integrateing salicylic acid with acetic anhydride.The second ester product is oil of wintergreen, or methyl salicylate, which we prepare by allowing salicylic acid to react with methyl alcohol. This compound, which has a familiar odor is utilize as a flavoring agent and in rubbing ointments. twain of these reactions are shown below. Preparation of acetylsalicylic acid H H C C H C H C C C C O O H O H + O H3C H3C C O C O H H+ H H C C C H C C C C O O O C O CH3 + O C H3C O H H salicylic acid acetic anhydride acetylsalicylic acid (aspirin) acetic acid Preparation of methyl salicylate H H C C H C H C C C C O O H O H + H O H H CH3 H+ H C C C C C C HO H + O H H O C O CH3 salicylic acid methanol methyl salicylate (oil of wintergreen) water This experiment illustrates approximately(prenominal) properties of organic synthesis. While wellspring-nigh(prenominal) product compounds in the experiment are esters of the same compound (salicylic acid), they are quite different in structure. Aspirin involves a reaction of the -OH group of salicylic acid, while methyl salicylate involves a rea ction of the COOH group of salicylic acid. Organic chemistry is the broad field of studying the tremendous variety of such reactions of organic functional groups. Purification by Re lechatelierite.After preparing the aspirin, we will purify it. Most solids sack up be purified by recrystallization, at a cost of lower part support. Recrystallization is usually d i by dissolving the substance in a suitable solvent, which is hot. If insoluble particles are present, the hot solution is tryed to remove them (we will skip this hot filtration step). The solution is allowed to cool slowly, and is eventually cooled in folderol. The crystals that form slowly are more pure than the original solid. Characterization by Melting head teacher. A simple characterization technique that abide be very useful in determining purity is liquescent allude.It does not, however, check much slightly the identities of the impurities. Pure materials usually have characteristic temperatures at which th ey melt, or a narrow temperature range (less than one degree) over which they melt. adulterated compounds usually melt at a lower temperature, over a wider range. HAZARDS Both acetic anhydride and sulphuric acid are reactive chemicals that crapper urinate a serious burn on contact with the skin, and are irritating to the eyes. In case of contact with these chemicals, wash the skin thoroughly with soap and water. Do not dispose of any chemicals down the sink. sort of use the waste containers provided.NOTE The aspirin you will make is muddied and must(prenominal) not be interpreted internally LABORATORY OBSERVATIONS AND DATA Be sure you make plenty of good qualitative observations, noting initial colors, odors, etc. , and any changes that occur during the experiment. Clearly label all numerical data. We will spend a little over one sept day on this lab. In the first day, you inquire to prepare and recrystallize your aspirin. If time permits, you rout out also prepare the met hyl salicylate. If not, this can wait until the second day when you will also take thawing points of your crude and purified aspirin samples.PROCEDURE Synthesis of aspirin. Weigh out approximately 2. 1 g of salicylic acid (record film mass), and transfer it to a clean, dry 6 inch test thermionic tube. handling the dispenser to carefully confer 3 mL of acetic anhydride (density = 1. 08 g/mL) to the salicylic acid. accordingly add 3 drops of concentrated sulfuric acid, H2 SO4 , to the reaction mixture (it acts as a catalyst and speeds up the reaction). Put the test tube in a beaker of change state water in a poser and fondness for five minutes after most of the solid has dissolved. Stir the mixture with a glass rod to break up any lumps.Pour the circumscribe of the test tube into a 50 mL Erlenmeyer flask containing 25 mL of water. Swirl the flask for a few minutes to mix the solutions and get rid of any unreacted acetic anhydride. (The acetic anhydride reacts with water to produce acetic acid. ) Place the flask in an ice bathtub and go over for a white solid to crystallize out. Occasionally a reaction will yield an oily product that resists crystallization. If that happens, scratch the bottom and sides of the flask with a glass stir rod to help start crystal formation, or warm the mixture just until the oil dissolves, and then re-cool.Allow 10 minutes for crystallization to occur. Meanwhile put a wash store of distilled water in some ice and prepare a Buchner funnel. leach the solid, being sure to use a trap flask among the Buchner funnel flask and the aspirator. Wash the solid with a small totality of cold distilled water. Discard the liquid filtrate in the designated waste container. Pre-weigh an desert watch glass, then scrape your aspirin product off the filter paper onto the watch glass. record book this yield of crude aspirin. Use a bit of the solid product to pack a melt point capillary tube to use the second week to find the melting point of your crude product.Recrystallization of the crude aspirin to form pure aspirin Put 15-20 mL of distilled water on a hot plateful to begin warming. Dissolve your crude aspirin product in about 5 mL of 95% ethanol in a 50 mL Erlenmeyer flask. If some of your aspirin fails to dissolve, do the following Prepare a warm water bath by using a beaker of water (about 50 mL in a 250 mL beaker), using a hot plate to heat the water bath. DO NOT using up A FLAME OR BUNSEN BURNER THE ETHANOL IS FLAMMABLE. Warm the Erlenmeyer flask containing the aspirin and ethanol in the warm water bath.When the aspirin has dissolved, add 15 mL of warm distilled water (50 o C approximately). If any crystals form at this point, reheat the mixture in the water bath to re-dissolve them. Let the solution cool slowly, with the mouth of the flask covered by a watch glass. When it is at room temperature, place it into the ice bath and leave it there a full ten minutes. After crystallization is complete, filt er the crystals in a Buchner funnel, wash them with a little ice cold distilled water (put your squeeze bottle in the ice), and suction for several minutes. Discard the liquid filtrate in the designated waste container.Scrape the solid into a pre-weighed beaker and put in your drawer, lightly covered with a tissue. Do not cover it tightly because we want your product to finish drying until the next class period. You will need to get a final mass of this purified aspirin after allowing it to dry for a day. You will also take a melting point of the purified aspirin. When finished with the experiment, place your aspirin product in a test tube and stopper it. Label the test tube with your name, the name of the compound, and the date. Your instructor will collect this product. Synthesis of methyl salicylate.Place 0. 5 g of salicylic acid and 3 mL of methyl alcohol in a large test tube. Add 2 drops of concentrated sulfuric acid and then place the test tube in the hood in a water bath at 7 0 o C for 15 minutes. The boiling point of methyl alcohol is 64. 6 o C, so point the mouth of the tube away from some others and stay off overheating, to minimize bumping. bank line the odor before and after heating. Allow your methyl salicylate to cool to room temperature, then stopper the test tube. Add a label with your name, the compound name, and the date. Your instructor will collect this product.Determination of the Melting Point of your aspirin. You should already have a capillary tube packed with your impure aspirin. Now pack a tube with your pure aspirin. Put your two tubes in the melting point apparatus and slowly heat your samples. discharge the temperature at which each starts to melt and the temperature at which it has all melted. (Your instructor will give you more instruction on these procedures. ) RESULTS Calculate the theoretical yield of aspirin from the balanced equation given in the introduction. You will need to add up molar masses by counting the atoms sho wn in the structures.Be sure to determine the adjustment reagent, either salicylic acid or acetic anhydride. You will need to use acetic anhydrides density, 1. 08 g/mL. interpret this work clearly in your deal. Watch significant figures and units. Also report the masses of your crude and purified aspirin samples, and the percent yield of your final, purified aspirin. DISCUSSION get what your melting points say about the purity of your initial crude product and your recrystallized product. Pure aspirin has a melting point of 135o , while salicylic acid has a melting point of 157-159o .Impure compounds normally have lower melting points and broader melting ranges than if pure, even if the impurity would have a higher melting point itself. List all the compounds that could be mixed in with your aspirin product as impurities, i. e. all reactants, solvents, and other products. You should have six compounds also aspirin. Briefly describe the source of each compound. Considering facto rs such as limiting reagent (which you just calculated), and procedural steps which may have removed some of these compounds, which compound(s) do you think are most likely to contaminate your aspirin product? ExplainQUESTIONS 1. unseeable spectra are often used to get a quick look at the purity of a product. IR spectra of aspirin, as well as the salicylic acid and acetic anhydride used to prepare it Selected Infrared Frequencies are shown below. Consult the structures of these three Absorption Range, cm-1 Bond Type compounds from the introduction. pull in ones horns from our experiment 3600-3200 (usually broad) on IR that different bonds show up at different frequencies in O H the IR spectrum. Prepare a listing for each compound, C H 3300-2800 showing bonds and their IR frequencies taken from the B H 2650-2300 spectra below.You need consider only those bonds listed in C ? N 2260-2220 the table at right. (It is hard to read the frequencies on the connect spectra accurately, so just approximate. The frequency values listed on the x-axis in the figures are 4000, 3000, 2000, 1500, and 1000 cm-1. ) 2. Look at the IR spectra again. Assume that you ran an IR spectrum of your aspirin, simply that it was contaminated with unreacted salicylic acid. At what frequency in the spectrum would you look for evidence of this contamination? Explain your reasoning. IR Spectrum of Aspirin (KBr pellet)IR Spectrum of Salicyclic Acid (KBr pellet) IR Spectrum of Acetic Anhydride (liquid thin film) 3. 1 H NMR spectra of salicyclic acid and aspirin are shown below. Note that both have small, broad peaks near 11 ppm that were artificially intensify to make them obvious on these spectra. The peaks around 7-8 ppm are all doublets, triplets, or messy multiplets the other peaks are singlets. How many types of H should be expect for each compound based upon their structures? The two structures share many common features, and thus their spectra should be similar for these common feat ures.Likewise, each structure has some unique type of hydrogen not gear up in the other. These should result in differences between the spectra. By simply comparing the structures and the spectra, decide which hydrogens on the structures give rise to which peaks. You wont be able to impute all the peaks this way, but do as much as you can and explain your reasoning. 4. The Merck Index is an extremely valuable reference that can be found in the Reference Section of the Fintel Library as well as several reading rooms on 5th traumatize Trexler.It is an especially good place to find basic knowledge on organic compounds. Look up aspirin in The Merck Index. Summarize the information it gives about the solubility and decomposition of aspirin. Record the pas seul number and where you found this book. 5. The CRC Handbook of Chemistry and Physics, often simply called The CRC, provides less information on each compound than The Merck Index does, but covers more inorganic compounds and inc ludes hundreds of pages of other facts useful to chemists.In the CRC find the multipage table entitled Physical Constants of Organic Compounds. indoors this table, find salicylic acid (some old editions may list it as 2-hydroxybenzoic acid). Record the information given about salicylic acids melting point, boiling point, and solubility. You will probably need to consult the listing of Symbols and Abbreviations given one or two pages in front of this huge table. Record the edition number of the book and where you found it.