Jylliana
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Methyl salicylate (Wintergreen oil)
Today I tried to make wintergreen oil(methylsalicylate). Everything went according to plan, because my product smells like christmas  , but something happened that I cannot explain, so I was wondering if any of you
might be able to help me.
I followed the instructions from this website: http://chemie.vermaseren.nl/Proef54.htm
but since it is Dutch, I will translate it here for you:
The only difference is that the Dutch website uses Aspirin tablets, and I used the same amount, but just pure acetylsalicylic acid.
Procedure:
1. Add 50ml demineralized water to an erlenmeyer.
2. Heat up a waterbath to 70 degrees Celsius.
3. Add 10ml of methanol to a test tube.
4. Slowly, with an eye on the temperature, add 1ml 98% sulfuric acid.
5. Add 2 grams of acetylsalicylic acid.
6. Place the test tube in the water bath and heat it for 15 minutes, longer is better.
7. After heating, add clear liquid in the test tube to the erlenmeyer with 50ml of demin. water.
- This is where the weird thing happened. As far as I know, two esters and water should be the reaction product, but when I
added the liquid to the water, a white, fluffy, crystalline solid appeared.
I'll describe what I did next, it's still like the procedure described on the website above.
8. Filter the liquid.
9. Add the now clear liquid to a separatory funnel.
10. Separate the two layers.
- The top layer clearly smelled like wintergreen, so the reaction took place, but can anybody tell me what that white solid
might be? I see no record of that it should form anywhere.
[Edited on 19-12-2014 by Jylliana]
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Jylliana
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I could always say that the white solid is snow, but that's probably not the case, hehe 
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gdflp
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My guess is that the sulfuric acid hydrolyzed the acetylsalicylic acid to salicylic acid and acetic acid. These then began esterifying with the
methanol, but the reaction didn't go to completion. Salicylic acid is soluble in methanol, but relatively insoluble in water so when you quenched the
reaction mixture with water, the remaining salicylic acid precipitated out. I would test the acidity of the precipitate.
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Amos
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Esterifications like this are reversible reactions, and there's always an equilibrium between your products and reactants involved. So your
precipitate is likely just crystals of salicylic acid that either never reacted to begin with or formed as a product of hydrolysis in the mildly
acidic water.
If you wanted to improve your yield of the ester, you would add a greater amount of methanol (Probably at least 20mL) and also more sulfuric acid,
which acts to sequester any water produced as a product of esterification.
Oh, and I'd advise against using acetylsalicylic acid; the smell of your product may be nice, but it'd be better without excess acetic acid present.
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Jylliana
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That sounds very plausible. I don't smell any acetic acid in my product, but the precipitate looked like acetylsalicylic acid, now that you mention
it..
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DraconicAcid
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I'd guess the precipitate is either unreacted ASA, or salicylic acid.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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vmelkon
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Why do you add water in the beginning?
This is a fisher esterification reaction.
One of the products is H2O and it is best to have as little as possible to drive the reaction to the right hand side. (Le Chatelier principle).
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gdflp
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She's not adding water in the beginning. She's adding water to an erlenmeyer to use as a water bath, and then to quench the reaction products. It's
a little confusing in the order written.
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