As I really like he odour of this compound I wanted to make some.
I dissolved 5,8g of salicylic acid in 20mL of methanol and added 1mL of conc. sulfuric acid. I heated on a water bath at 40-50C overnight, and then
next day, I refluexed for about 1,5 hours. Next most of the methanol was boiled away by removing the condenser. The reaction mixture was poured in
40mL of water. An emulsion formed, so 15-20mL of ethyl acetate were added and some NaCl. After seperating the aqeous layer was washed again with 10mL
ethyl acetate. Next the two extracts were combined and washed 2 times with 5% sodium bicarbonate solution.
Then it was dryed with CaCl2.
The ethyl acetate was boiled away on the water bath, until boiling stopped.
I obtained about 5-7mL (not measured) of liquid, still having a smell of ethyl acetate but also methyl salicylate (I know the odour).
To be sure of it's presence I added a few drops of the liquid to 2mL 2M NaOH. Immediately a white precitipate formed, wich redissolves on boiling!
Does this mean that I mostly have salicylic acid dissolved in some methyl salicyalate and ethyl acetate? As methyl salicylate should't hydrolyse so
fast in cold NaOH right? Anotehr surprise was, that when excess 4M H2SO4 was added, no salicylic acid precitipate was formed (very insoluble in
water).
Does anyone know what I did wrong, and what tests I could perform on the product? I really wish i had H-NMR at hand.
Sorry if I made some mistakes i typing this post, i had to be quick as I am having dinner now.
[Edited on 27-5-2009 by Jor]Arrhenius - 27-5-2009 at 08:25
I don't think you need to warm it overnight. Do not concentrate down the methanol after the reflux, because you're just concentrating the sulfuric
acid, which may cause problems with your product. Better to go straight to aqueous workup. Using a base wash in your workup will help to remove
unreacted salicylic acid. Better to use a known procedure:
Dissolve salicyclic acid (5.6g, 40mmol) in methanol (20ml, 480mmol). Add 1.2ml concentrated sulfuric acid, a boiling chip, and reflux for 2 hours.
Cool to room temp, dilute with 10ml water (or brine) and extract with 3x10ml ethyl acetate*. Combine the ethyl acetate, wash with 10ml water then
10ml sat. NaHCO3. Dry the combined organic phase and evaporate.
*I have substituted ethyl acetate instead of DCM in this procedure. You're quite likely to get a tough emulsion with ethyl acetate, so just keep
adding water until you can get two phases.
In my opinion, what you need is TLC, not NMR.
[Edited on 27-5-2009 by Arrhenius]panziandi - 27-5-2009 at 09:54
Hey Jor: I think you could skip the over night part. Just reflux for a couple of hours. I agree with Arrhenius and skip removal of methanol step, just
pour into brine and extract into ethyl acetate (couple of washes) combine the organics wash with saturates bicarbonate until no more gas is evolved,
and then collect and dry organic layers. Evaporate the solvent.smuv - 27-5-2009 at 14:48
Quote:
The ethyl acetate was boiled away on the water bath, until boiling stopped.
I obtained about 5-7mL (not measured) of liquid, still having a smell of ethyl acetate but also methyl salicylate (I know the odour).
To remove the last traces of ethyl acetate you either need to let the stuff sit under a good vacuum for a while, or heat the solution under free flame
until the methyl salicylate just starts to come over. Unfortunately high bp oils need this treatment to remove the last traces of solvent. panziandi - 27-5-2009 at 14:56
Yes a distillation of the product (discarding the first short forerun) would be ideal Jor, although if you aren't too worried about the trace of ethyl
acetate and possible salicylic acid (although should be removed by NaHCO3) then I wouldn't both with this step.DJF90 - 27-5-2009 at 18:42
We distilled the methyl salicylate we made in the lab, bpt. ~220C IIRC but this is going back a year or so ago. I think the procedure was something
like this:
15ml of methanol and 8g of salicylic acid are added to a 50ml pear shaped flask with a few boiling chips. About 1ml of conc. sulfuric acid is added,
and the mixture refluxed for 1hr 30mins. The reaction mixture is poured into a separatory funnel (we used 50ml ones but would have preferred 100mls),
10ml of ethyl acetate is added to the sep. funnel, and 5ml of ethyl acetate is used to rinse the flask, which is then added to the sep funnel. The
extract is washed with 4 x 10mls of sat. NaHCO3 solution and then dryed over Na2SO4 (anhydrous). The extract is then filtered into the distilling
flask, distilling carefully two fractions, the first being the ethyl acetate (bp. 77C) and the second from 220C, being the product methyl salicylate.
As I said this is from memory but I'm pretty certain the numbers are right... This was my favourite synthesis at school and so I seem to have
remembered it pretty well.Skyjumper - 1-4-2010 at 17:17
I'm doing this now. I refluxed 10g of salicylic to 100ml of methanol for an hour (I ran out of time) I smell the ester smell but did I reflux it long
enough? and I really dont want to make another ester (the ethyl acetate) to sep it out. Would say, Hexanes or toluene work as an alternative? DJF90 - 2-4-2010 at 03:26
Your proportions seem way out. If I remember correctly, when I did this preparation I followed a textbook procedure and used 9g salicylic acid with
15ml methanol, and 0.5-1ml conc. H2SO4 as a catalyst.... You did remember the catalyst right?!Skyjumper - 2-4-2010 at 12:19
oh course. I only added maybe 2 mils (maybe...) I think I may redo the expariment. I was going off of the setup on this site (it was like .2g to 2ml,
thus 1gram per 10ml, 10g per 100ml) But ether way Its sitting in my lab through the holiday. I think I will reflux it some more (add more of both
acids?) Nicodem - 2-4-2010 at 13:30
How about being a bit more original and synthesizing methyl salicylate directly from acetylsalicylic acid (aspirin)?
While the carboxylic group esterifies with MeOH, the aryl acetate ester function should transesterify to methyl acetate under the conditions of reflux
in methanol and H2SO4 as catalyst. And so you have a direct one step aspirin->perfume transformation.
You can use toluene or hexanes for the extraction, but it will work better if you first add just enough NaHCO3 to neutralize all the H2SO4 used and
then evaporate the methanol. Then dissolve in toluene or hexane and wash with NaHCO3(aq), water, etc. Using these solvents on the reaction mixture
diluted with a small amount of water (as described above) will not extract all of the product from aqueous methanol, because toluene is not polar
enough (and so much worse with hexanes). If you skip the methanol removal and still want to stick with toluene or hexanes, then make sure you add at
least 4-times more water than the volume of methanol. However, toluene has a higher boiling point so that just evaporating it in vacuo or using short
path distillation (and no distillation column) might not remove all of it.Skyjumper - 2-4-2010 at 20:22
After thinking, I think what I will do is add another 20 grams of salicylic (I have 100mls to 10grams now) to be able to react off the rest of the
methanol. Apparently the prep methods highlighted in the article I was referring too (I didn't want to balance the equation :p) was very off. From
there I guess I will go ahead and make the etOH acetic ester to separate my oil of wintergreen, and fractionally distill off the excess meOH and ethyl
acetate. From there I should have pure (enough) oil of wintergreen left in my boiling flask.
good idea? or should I just ditch my current mixture, and start over (I really dont want to do this!)
My figures:
I have 10 grams of salicylic acid, and 100 mls of methanol. Per the process highlighted above, I actually want a 5.6grams of acid to 20mls of alcohol
ratio. By upscaling these numbers I should have a total of 28 grams of acid for my 100mls of alcohol. I will also add another 7-10 mls of sulfuric to
make sure I have an adequate amount of catalyst in there.
I suppose I should reflux it much longer after adding the additional entropy51 - 3-4-2010 at 12:17
Skyjumper, based on the prep in Fisher's Laboratory Manual of Organic Chemistry, probably in the forum library, you should add about 14 gm additional
salicylic acid and about 5 mL H2SO4, reflux 2 or 3 hours, and distill off the methanol. The ester left in the pot should be washed with some H2O,
then some dilute Na2CO3. Fisher says to dry over Na2SO4 and distill under vacuum. But the water wash should remove the H2SO4 and any remaining
methanol, so if you don't have vacuum it should be fairly pure without distilling. The ester is not very soluble in H2O, about 1 gm in 1500 mL
according to the Merck Index.
I wouldn't add ethyl acetate or anything else.Skyjumper - 3-4-2010 at 13:30
Thanks a ton. I'l add another 14 grams and let it go for another 2 hours (probably split over 2 days) reflux. Then follow the rest of your protocol.
