Methyl Salicylate (Oil of Wintergreen)

Here’s a simple synthesis of methyl salicylate (oil of wintergreen), for those that just started (organic) chemistry (though of course, even if you are a bit more experienced, nothing beats a minty smelling flask/test tube ).

Necessary reagents:
Methanol, CH3OH
Salicylic acid, OHC6H4COOH
Concentrated Sulfuric Acid, H2SO4

The procedure is a Fischer esterification and is quite simple, and can be followed below (I used point form for ease of following and simplicity). Note that I did this on a microscale, but if you have the right apparatus, this can easily be scaled up. You could also get more complicated by using a Dean-Stark trap for esterification, etc.

1) Dissolve 0.2 grams salicylic acid into 2.0 mL of methanol in a 5 mL round bottom flask.

2) Add 4-5 drops concentrated H2SO4

3) Add a few boiling chips to promote smooth boiling.

4) Reflux for 40 minutes.

5) After 40 minutes, remove and isolate product.

Discussion: In step 4, I used a hot water bath and not a sand bath, which is not the best method. The water vapours that come off from the water bath cause the condenser to heat up much too quickly, and some of the product vapour managed to escape the condenser. In addition, I didn’t have a pipe cleaner handy (to wrap around the condenser to keep it cool) so I improvised and used some small strips of wet paper towel in an attempt to keep the condenser cool.

I also did not bother isolating the product (i.e. separating from the water, methanol that is left over, etc.) as I don’t have the necessary reagents.

If you want to purify your product, you can do the following:

1) Pour the mixture into a test tube and add 4 mL diethyl ether.

2) Remove the aqueous layer with a (Pasteur) pipette.

3) Pour the organic layer into another (dry) test tube and remove any residual water.

4) Add 2 mL NaHCO3 solution and mix. This will neutralize any remaining acid.

5) Transfer the ether layer to another (dry) test tube and add CaCl2 pellets until the product is dry.

Some pictures:


Image of the initial setup (paper towel taken away for better image)


Image of the setup in the hot water bath (paper towel taken away for better image)

References: Williamson, Kenneth. Macroscale and Microscale: Organic Experiments. 4th Edition. Boston: Houghton Mifflin Company; 2003. pg. 486 – 497

Edit: Some minor coding problems

[Edited on 6/12/05 by Darkblade48]

Thanks for the compliments, I thought it was poorly written, as I typed it up on the spot without much prethought (more like I just copied almost directly out of my lab notebook that I keep...)

I'm not quite sure what you are referring to as the "metal rod gizmo" in the condenser, are you talking about the needle? If so, it is simple a hollow needle there to relieve pressure buildup. It can clearly be seen in the first picture.

However, if you are talking about what I think you're talking about, then it's just the glare of the glass walls of the condenser, due to my bad photography skills There actually is nothing else inside the condenser other than the aforementionned needle.

Edit: I was just curious as to the isolation step. Williamson calls for ether, but would it be feasible to try this with dichloromethane (DCM)?

[Edited on 6/12/05 by Darkblade48]

I thought you had referred to my poor photography skills, guess you were referring to the needle afterall

I just thought I would report the results of my attempt to make this pleasant smelling substance .

I followed the procedure from vogel but scaled it up.

Equipment:
1L round boiling flask
400mm condensor (west)
Walmart hotplate
Walmart submersible air pump (for condensor)
Seperatory funnel

Materials:
160g Salicylic Acid
475ml Methanol
50ml H2SO4 (94%)
666 g NaHCO3

Procedure:
Combine the salicylic acid and methanol in flask. Slowly add H2SO4 until everything is nice and mixed. Reflux in water bath for 4 hours. The temperature in the flask was measured to be about 74C. After 4 hours, take off the condensor and methanol evaporate for about 45 minutes. You may see white precipitate forming in methanol. (only thing it could possible be is unreacted salicylic acid) Remove from water bath and let the flask/mixture cool, you will notice two distinct layers forming, the one on the bottom is the methyl salicylate.

Add the cooled mixture to a seperatory funnel, add 300ml chilled water. Seperate the layers, keeping the lower one. Make a sodium bicarbonate solution and keep adding it until it's neutralized. Seperate again. The product is fairly pure, though I'd at least dry it. Drying can be done via MgSO4, which seemed to work excellently for myself. If you aren't using it as perfume then redistillation is not necessary IMHO.

Theoretical yield- 148ml
Final yield- 125ml
Percent Yield: 84% .

I would say very succesful overall.

Now my question is, what other uses does it have besides smelling/tasting good?

[Edited on 25-3-2006 by PainKilla]

Are you implying poisoning as a use?

Slightly off topic but does anyone know offhand the ester for the banana smell?

Quote:

Originally posted by PainKilla Are you implying poisoning as a use? Slightly off topic but does anyone know offhand the ester for the banana smell?

And it is toxic only in large quantities. It is actively used as a flavoring agent in candy. A dose of a tablespoon is lethal to small children. So if you are sure of your purity, it is usable in food with great respect to the concentrations involved.



Various conditions after 7 days. The one on the left is commerical grade, the one in the middle is made from salicylic acid from aspirn, the one the the right is the control.

Quote: Originally posted by PainKilla

... I followed the procedure from vogel but scaled it up. Equipment: 1L round boiling flask 400mm condensor (west) Walmart hotplate Walmart submersible air pump (for condensor) Seperatory funnel ...

Quote: Originally posted by Fenir

Would it be possible to substitute sodium bisulfate for the sulfuric acid? Thanks for any help, I am just getting into esterfications.

Quote: Originally posted by Awesomeness

You used an air pump for your condenser? Were you running air through your condenser, or did you submerge the pump? I'd be concerned with the water resistance of an air pump.

<strong>Awesomeness</strong>, <strong>PainKilla</strong> hasn't been active since 10/18/09. You might want to glance at the dates of posts you're responding to.