Copper Aspirinate Synthesis
Copyright 2003 by Brian Fraser
Disclaimer: The following is a summary of the procedure I used to make copper aspirinate complex (not compound). I offer it here for informational purposes to show that copper aspirinate can be made with commonly available materials and equipment. A similar procedure is typically done by second-year college chemistry students as a laboratory exercise in a setting supervised by a professional instructor. I do NOT recommend that people do this at home. Some aspects of these procedures are hazardous, and the typical home kitchen simply has too many distractions and interruptions for a student to carry out these procedures safely. Your wife (or mom) will also be furious if you get copper sulfate stains on her kitchen counter!
The method presented here is a traditional one. But there are others. A hybrid electrochemical one using aspirin, water, copper wire, and electrolysis can be found at http://chem.sci.utsunomiya-u.ac.jp/v11n2/PerezBenitez/PEREZ_BODY.html ("Hybrid (Electrochemical-Chemical) Single Crystal Synthesis of Copper Aspirinate Starting from an Aspirin Tablet: an Undergraduate Bioinorganic Experiment", Aarón Pérez-Benítez, Miguel Ángel Méndez-Rojas, Sylvain Bernès and Enrique González-Vergara , 2008)
Commercially prepared copper aspirinate is often used to treat rheumatoid arthritis. Readers who are interested in this medical use may want to explore alternative therapies as well:
"Unexpected Benefits of Olive leaf Extract", Julian Everson (June 2013)
Copper Aspirinate synthesis (kitchen method)
Equipment and Materials required
1. Saturated copper acetate solution. See procedure below.
2. Pure aspirin crystals. See procedure below.
3. Ethanol (95%; liquor store ethanol like Everclear (190 proof, UPC 088352100036) is what was used here.
4. Vacuum filtration facilities (Büchner funnel, coarse and medium porosity filter paper, aspirator, filter flask, seals, tubing, clamps, stand, etc. These common lab tools are not absolutely necessary, but can speed things up considerably.)
5. Containers for liquid such as Rubbermaid 24 fl. oz. servin' saver tm (used here as a "beaker").
1. Add 1 fl. oz. of saturated copper acetate solution to a beaker.
2. Dissolve 1 tsp (teaspoon) pure aspirin crystals in about 1 fl. oz. of ethanol (95%) in another beaker
3. Pour the aspirin solution into the copper acetate solution. Stir occasionally.
4. Dark blue crystals will gradually form on the sides and bottom of the beaker. The initial layer will form immediately if the beaker has been freshly cleaned and scoured. The layer will gradually thicken and become bluer and darker. This process may take several hours. The endpoint is reached when the liquid has turned a light blue and no more blue crystals are forming on the walls of the beaker. (You can verify the endpoint by siphoning the clear liquid, evaporating it in a separate container, and checking the residue. The residue should be mostly aspirin crystals.)
This procedure requires no heating. If you heat the liquid to increase the reaction rate, be aware that aspirin can hydrolyze into acetic and salicylic acids in a moist or liquid environment. If that happens, the liquid will turn dark green, and the yield of copper aspirinate will be greatly reduced.
5. Cool the mixture in a refrigerator.
6. Scrape the crystals off the sides and bottom of the beaker. Then vacuum filter the whole mixture. (Save the first filtrate in a separate container if you do ethanol solvent recycling.)
7. Wash the blue powder on the filter with cold distilled water.
8. Dry the powder and filter paper in an oven at about 120F. Store the dry powder in a small dark bottle with a label identifying the contents and the date of creation.
Substitute isopropanol (99%) for the ethanol in step #2 and use 1/2 teaspoon, instead of 1 teaspoon, of aspirin crystals and 1/2 fl. oz. isopropanol instead of 1 fl. oz of ethanol. After several hours of initial crystallization, add 1/2 fl. oz. of distilled water and place the beaker in the refrigerator and wait a few more hours for more crystals. This variation gives about the same results as the ethanol procedure. Its advantages are that it uses less excess aspirin and a less expensive alcohol.
Aspirin purification (kitchen method)
Equipment and Materials required
1. One bottle of 1000 commercial aspirin tablets (preferably the uncoated kind).
2. A pint or two of isopropyl alcohol (99%). This is usually available from a hardware store. Sometimes it can be found in a drugstore (UPC: 341226909730 ) Isopropanol is extremely flammable, so be very careful not to expose vapors to hidden or unexpected ignition sources.
3. A couple of gallons of deionized or distilled water.
4. Three, 24 fl. oz. wide-mouthed polypropylene containers with covers, such as Rubbermaid servin' saver tm.
5. Oven thermometer (easily read dial type is best)
6. Modified turkey baster (see construction procedure below)
7. One kitchen (with sink, refrigerator, oven, etc)
1. Dump a few hundred aspirin tablets into a wide-mouthed container.
2. Add distilled water to the container and stir. This will break up the aspirin tablets and dissolve the hydroxypropyl methycelluose coating that is usually used to coat aspirin tablets. Let the mixture settle for an hour or so in the refrigerator.
3. Siphon most of the water out with a modified turkey baster.
4. Repeat steps #2 and #3 a total of three to five times. This will largely get rid of the methycellulose coating, which tends to clog filters. You might not need to repeat these steps if you use uncoated aspirin.
5. Vacuum filter the mixture from #4 and dry the powder in air. (Caution: aspirin tends to decompose when heated in a moist environment).
6. Add the powder to a quart container. Add about a half-cup of isopropyl alcohol (99%). Stir. This will dissolve part, but not all, of the aspirin. Let the mixture settle.
7. Vacuum filter the above mixture using medium porosity filter paper. Pour the filtrate into a clear glass container for inspection. If the filtrate is not clear, re-establish vacuum on the filter, and filter it again. (Sometimes simply letting the mixture settle and then siphoning the clear liquid with a turkey baster is more effective than filtration; the latter, however, may be faster.)
8. Pour the clear filtrate containing the dissolved aspirin into the second container, cover it, and place it in the freezer (about 5 F or so). After an hour or so the aspirin will crystallize out of solution. Return the powder on the filter to its original quart container.
9. After the aspirin crystals have formed, remove the container from the freezer. Carefully decant the liquid back into the first container that contains the impure aspirin powder. Then scrape out the pure aspirin crystals into a third container.
10. Cover this first container (impure aspirin powder and recovered isopropanol) and let it warm to room temperature. Agitate it occasionally so that more aspirin will again dissolve.
11. Repeat steps 7 through 10 until you have recovered all the aspirin, and the filter paper has only a thin layer of the excipients (typically calcium phosphate, starch, talc, etc. These impurities are added to the tablets to help them break up in water). Discard the filter paper. Dump the isopropanol down the drain, and wash it down with some tap water.
12. Using new filter paper (medium porosity), filter any remaining isopropanol from the recovered aspirin crystals (third container). Rinse the third container with distilled water and wipe it dry. Dump the filtered crystals back into the third container and cover them with cold distilled water. Re-establish vacuum on the filter and filter the crystals again. This will rinse off any remaining isopropanol. Discard the liquid. (Repeat the procedure if you can still smell isopropanol on the crystals).
13. Finally, gently dry the aspirin crystals. (I dried mine in an oven at 120 F. If you do this, BE SURE you have rinsed the crystals well enough so that there are no isopropanol vapors present. Isopropanol forms explosive vapors with air, and allowing these to accumulate in a confined space is a recipe for serious trouble. Also, aspirin tends to decompose when heated, especially in hot water, so I use only a warm temperature setting. )
Copper acetate synthesis (kitchen method)
Equipment and Materials required
1. Copper sulfate pentahydrate 99%. This is usually available from a hardware store in the form of a product used to kill tree roots in sewers and septic tanks, such as Roebic K-77.
2. Arm and Hammer Baking soda (sodium bicarbonate).
3. A couple of quarts of distilled vinegar (5% acetic acid).
4. A Pyrex casserole dish (22 x 11 x 6 cm or similar)
5. Vacuum filtration facilities.
6. Various clean, quart containers.
Preparation of filtered copper sulfate solution
1. Dissolve 3/4 cupful of copper sulfate crystals in about a quart of warm distilled water.
2. Vacuum filter the solution through coarse porosity filter paper. This will filter out suspended solids (metal flecks, "dirt", etc.). Pour the filtrate off into a clear inspection container. Vacuum filter the solution again with medium porosity paper until it is clear blue. Note that the filtrate may still contain significant impurities (lead, arsenic, cadmium, etc.) at this point. Remember that this product is normally used in sewers.
3. Save the clear blue solution for later use.
(4. If you want higher purity copper sulfate, you can re-crystallize it at this point.)
Preparation of sodium carbonate solution
1. Pour a cup full of sodium bicarbonate into a Pyrex casserole dish. Add distilled water sufficient to dissolve it.
2. Heat the solution in an oven to about 200F. This will cause the bicarbonate to decompose into the carbonate with the evolution of carbon dioxide. The end result will be a solution of sodium carbonate.
3. Let the solution cool to room temperature. Carbonates are somewhat less soluble than bicarbonates; add more distilled water if necessary to keep the material in solution.
Preparation of copper carbonate
1. In a large container, gradually combine the copper sulfate solution with the sodium carbonate solution. A blue-green precipitate will immediately form along with the vigorous release of carbon dioxide. Let the precipitate settle out.
2. At this point the liquid portion will have either an excess of sodium carbonate or of copper sulfate. If you add a drop of sodium carbonate and see some precipitate form, then the bulk mixture needs more sodium carbonate solution added. Likewise, if you add a drop of copper sulfate and see a precipitate, then the bulk mixture needs more copper sulfate solution added. Make these adjustments as necessary until there is no longer an unambiguous formation of the blue-green precipitate.
3. Vacuum filter the mixture with a coarse porosity paper filter. Discard the liquid. Wash with cold distilled water and then refilter. This will wash out any excess sodium carbonate or copper sulfate.
Preparation of copper acetate solution
4. To a quart container, add the still moist copper carbonate powder from the previous step. Then slowly pour vinegar into the container. Carbon dioxide will evolve and copper acetate will form. The solution will gradually become a deep blue color. A blue-green precipitate may also settle to the bottom of the container.
5. Let the solution settle out. If there is a substantial amount of blue-green precipitate at the bottom of the container, add more vinegar. Try to dissolve most, but not all, of this precipitate. An excess of vinegar is harder to remove than a little of the precipitate.
6. Using coarse paper, vacuum filter the resulting copper acetate solution. Repeat until clear. Discard the paper. Save the blue filtrate.
7. Slowly evaporate the blue filtrate in a Pyrex casserole dish in an oven (150F) for several hours. Periodically scrape down the sides of the dish to prevent a build up of crystals. Continue the evaporation until some blue-black crystals of copper acetate begin to form (and do not redissolve). The mixture may also have some blue-green "pond scum" in it too.
8. Cool and filter the dark blue solution. Store it in a clear glass container for observation (a one quart vinegar bottle works fine). This is the saturated copper acetate solution that will be used to make copper aspirinate.
9. If you want to make copper acetate crystals, continue the evaporation process until blue-black crystals form. This will require evaporating most, but not all, of the solution. Impurities (and excess vinegar) tend to remain in solution instead of crystallizing out. Hence, it is necessary to discard a small portion of the original solution. Collect the crystals on the vacuum filter and discard the leftover liquid. Wash the blue-black crystals with a little bit of cold distilled water. Then dry and store them in a labeled container.
How to make the Modified Turkey Baster
Chemical separation procedures sometimes require decanting a liquid so as to separate the liquid from some sediment at the bottom of the container. An alternative, which is often useable, is to siphon it off. This is usually more precise than decanting. The simplest way to do siphoning is to use an ordinary kitchen turkey baster slightly modified for this purpose. The modification closes the tip somewhat so that siphoned liquid will not so readily drip out inadvertently.
1. Purchase a clear-nylon turkey baster from a grocery store.
2. Temporarily remove the squeeze bulb.
3. Carefully heat the baster tip over an electric stove burner until the tip softens and becomes translucent.
4. Close the tip by gently rolling it between a breadboard and a small piece of wood.
5. Let it cool. Drill a hole into the tip with a 1/16 inch drill bit.
6. Reaffix the squeeze bulb to the baster tube.
7. To get a better seal between the bulb and the tube, you can wrap the junction with a turn or two of self-fusing high-voltage rubber electrical tape (available at hardware or electrical stores)
Conversion of Aspirin to Salicylic acid (kitchen method)
1. Put about 4 tsp of pure aspirin crystals (see above) and 1/2 cup distilled water into a small, clean jar (such as one used for canning pickles or olives).
2. Place jar on a hot pad in a shallow pan in an oven set to about 225F. Let the aspirin hydrolyze into acetic and salicylic acids for an hour or two. (Add a little more water if all the crystals have not dissolved in the hot liquid.)
3. Cool the liquid in the refrigerator. You should see needle-like crystals.
4. Vacuum filter and wash the crystals with cold distilled water. This will remove acetic acid residue.
5. Dump the crystals out of the filter and air dry them. (they usually come out as a mat of fine needles). Store in a properly labeled bottle.
Conversion of Salicylic acid to Phenol
Phenol (carbolic acid) is an important disinfectant and germicide, as well as an important organic reagent.
According to the Merck Index (10th ed.), salicylic acid sublimes at 76 C, melts at 159 C, and will decompose into phenol and carbon dioxide when rapidly heated at atmospheric pressure.
Copper Salicylate Synthesis (kitchen method)
1. In a small custard dish, dissolve 1/4 tsp of sodium bicarbonate (baking soda) in a few of teaspoons of distilled water.
2. Add about 1/2 tsp of the salicylic acid crystals recovered from the conversion described above. Mixture will fizz a little. Stir until all the crystals dissolve.
3. Test the pH. Add more salicylic acid or bicarbonate to get pH of about 6 (slightly acid). This is now a solution of sodium salicylate.
4. Add copper sulfate solution drop by drop. An ugly green precipitate (copper salicylate) will form.
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