aga
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Minty Smell
Today i tried the esterification of salicylic acid to form methyl salicylate according to this utoob vid : https://www.youtube.com/watch?v=lJLP2bcXDqY
Half the amounts were used.
Big smile after 1.5 hours as there was a distinct minty listerine smell.
On washing with ice cold water, all the nice oil disappeared and semi-solid chewing-gum like lumps appeared.
Undeterred, the chewing gum was washed with sodium bicarbonate to remove acid and distillation attempted (reasoning=oils go to waxy solids when cold)
NO result other than a pile of dirty glassware, a blocked stop-cock in a sep funnel and a shed full of listerine smell.
I'll try again, after paying my wife the money i bet that i could do it easily, and today.
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blogfast25
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How cold was that water? The MP of methyl salicylate is only - 9 C. Perhaps it goes quite viscous at low temperature?
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aga
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The water was above zero, maybe 5 to 8 degrees.
As soon as the oil hit the water, chewing gum appeared.
Still smelt minty, but nowhere near as strong as before the water was added.
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blogfast25
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Sounds like unreacted salicylic acid then. I haven't watched the Utoob though. Is it 'worth' watching?
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j_sum1
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Yep. NileRed is good here. As is MrHomeScientist on the same topic. (NR uses salycylic acid. MHS uses aspirin.)
It is on the to do list.
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Amos
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I followed Nile Red's procedure to the letter, but interestingly enough, after boiling off most of the excess ethanol, upon decanting the reaction
mixture into water, the methyl salicylate FLOATED. So be sure that the layer you're extracting in the sep funnel step is the correct one.
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blogfast25
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Quote: Originally posted by Amos  | | I followed Nile Red's procedure to the letter, but interestingly enough, after boiling off most of the excess ethanol, upon decanting the reaction
mixture into water, the methyl salicylate FLOATED. So be sure that the layer you're extracting in the sep funnel step is the correct one.
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Salt in your water, pushing up density?
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cyanureeves
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i got the gummy stuff too and it was just as nice smelling as the liquid so i kept it.one time i did get the oil though but i lost track of what i did
different.i used cheap o'reilley's part store brake line antifreeze which was blue on all runs but on some runs i used different aspirins.also on
some runs i used salicylic and on some runs i just used acetylsalicylic acid(plain aspirin).i got equally smelling products so i was happy.my yields
were very little compared to all the three videos on youtube. i used a sandwich baggy for sep funnel and sometimes left them over night trying to sep
more oil.on some runs the gum would go to the bottom so i would decant because it would not float like the oil. the water i would separate from was
also minty smelling so my garage and tool shed smelled nice and tooth pastey.correction: the oil is supposed to sink but sometimes it would would only
form a thin layer on top that i would decant. i recall also having to cap the stuff because the smell would really get strong and irritating.
[Edited on 6-1-2015 by cyanureeves]
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Amos
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| Quote: Originally posted by blogfast25 | | Quote: Originally posted by Amos | | I followed Nile Red's procedure to the letter, but interestingly enough, after boiling off most of the excess ethanol, upon decanting the reaction
mixture into water, the methyl salicylate FLOATED. So be sure that the layer you're extracting in the sep funnel step is the correct one.
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Salt in your water, pushing up density? |
Nope, it was initially just cold distilled water. I suspect that the cold methyl salicylate was just too viscous and the addition funnel's inside area
was too small to allow the methyl salicylate layer to move itself underneath the water.
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aga
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Thinking about it, the video states that this an equilibrium reaction, and uses Le Chatelier's principle to push the reaction to the right by adding
an excess of methanol.
Once the methanol has been boiled off and a large amount of water is added, surely the same principle holds true, pushing the equilibrium back to the
left.
Is the reverse reaction a lot quicker than the forward reaction ?
There were certainly many oily blobs in the beaker before the water was added.
I'll try it again and neutralise the acid catalyst first.
Doh. Need to distill some more methanol for that.
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Oscilllator
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| Quote: Originally posted by aga | | Once the methanol has been boiled off and a large amount of water is added, surely the same principle holds true, pushing the equilibrium back to the
left. |
Well I think we can safely assume that methyl salicylate is stable at room temperature, since otherwise Listerine would become contaminated with
methanol over time. It *might* decompose in hot water, but if it was dumped in cold water the decomposition should be negligible.
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DFliyerz
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I actually have experienced something like this when dissolving acetylsalicylic acid in "denatured alcohol" (it was actually about 50/50
ethanol/methanol), where I got a very distinct minty smell and after washing the flask with water, I ended up with a goopy gum-like thing that I still
have a bit of stuck to the bottom of my wash basin.
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Texium
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I had problem with the methyl salicylate mixing with the salted water, because the density of a saturated Na2SO4 solution is
almost exactly that of methyl salicylate. So be cautious as you neutralize the solution. It can make it very messy, with little bubbles of the oil
floating up and down in the funnel if you need to add too much. I thought little of it until I realized that it wasn't separating nicely, and ended up
settling for having some dissolved in methanol until I make another attempt at it.
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