Cou
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Crap from "attempt to make isopropyl salicylate, something interesting happened"
Today I tried to make isopropyl salicylate, inspired by my success with making methyl salicylate by following nile red's videos. Wikipedia says
fischer esterifications work with secondary alcohols, while tertiary alcohols tend to dehydrate, so I thought this would be straightforward, just like
the methyl salicylate procedure.
in a round bottom flask I dissolved 7.4 grams of salicylic acid in 25 mL isopropyl alcohol. I added 8 mL 98% sulfuric acid, and the mixture
immediately become a purple slush with a gasoline odor (probably smell of propene).
Weird, so it seems fischer esterification is not gonna be straightforward with secondary alcohols. i didn't know secondary alcohols dehydrate that
easily. I think another way to do this would be to dissolve salicylic acid and sulfuric acid in turpentine, then add isopropyl alcohol dropwise while
refluxing. There might still be side products such as propene and diisopropyl ether, but at least those have much lower boiling points than isopropyl
salicylate.
Disregard that paragraph. Might just need to use a much smaller amount of sulfuric acid, since I didn't see it turn purple until I added a large
amount. 8 mL is a lot, which was based on nile red's methyl salicylate procedure.
[Edited on 14-12-2019 by Cou]
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G-Coupled
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That does seem like a lot of H2SO4 for use as a catalyst. 
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Pumukli
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Does propene smell like that? I was under the impression that propene is odourless.
Repeat it without isopropanol. What if salicylic acid decarboxylated to phenol (at least partly), the phenol got oxidized by the sulfuric acid
(purple) and smelled like gasoline.
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Σldritch
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I did something similar while trying to make Isopropyl Benzoate. I think i got some ester but a lot of tar smelling like new car. There are few smells
that can make me gag but that is definetly one of them. I never tried it again after that experience so all i can say is good luck. Oh and i think
there is some older thread on this which may have some insight.
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G-Coupled
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Ooh, I love that 'new car smell'. 
'Arleigh's van smelt like new electronics and long-chain monomers...'
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Cou
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I'm going to try it again with a much smaller amount of sulfuric acid, perhaps a mole ratio of 0.07:1 for sulfuric acid to salicylic acid
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Cou
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Quote: Originally posted by Pumukli  | Does propene smell like that? I was under the impression that propene is odourless.
Repeat it without isopropanol. What if salicylic acid decarboxylated to phenol (at least partly), the phenol got oxidized by the sulfuric acid
(purple) and smelled like gasoline. |
I repeated without salicylic acid. Isopropyl alcohol definitely reacts with 98% sulfuric acid to make the room smell like a gas station (probably
propene), and the mixture turns dark orange from some kind of polymerization probably.
Nothing similar happens when sulfuric acid is added to a mixture of salicylic acid and methanol. No purple slush and no gasoline smell. Just an easy
fischer esterifixation with no side reactions.
I'd like to see if this also happens with ethanol. If it readily dehydrates to ethene
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DavidJR
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| Quote: Originally posted by Pumukli | Does propene smell like that? I was under the impression that propene is odourless.
Repeat it without isopropanol. What if salicylic acid decarboxylated to phenol (at least partly), the phenol got oxidized by the sulfuric acid
(purple) and smelled like gasoline. |
Propene is definitely not odourless.
It doesn't at room temp but it does at higher temperatures. Though depending on the conditions you can get other products like diethyl ether,
ethylsulfuric acid, and diethyl sulfate.
[Edited on 15-12-2019 by DavidJR]
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G-Coupled
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| Quote: Originally posted by DavidJR |
It doesn't at room temp but it does at higher temperatures. Though depending on the conditions you can get other products like diethyl ether,
ethylsulfuric acid, and diethyl sulfate. |
That's interesting - so, is there a way to reliably make just or mainly Diethyl Ether using Ethanol and H2SO4?
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Cou
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| Quote: Originally posted by G-Coupled | | Quote: Originally posted by DavidJR |
It doesn't at room temp but it does at higher temperatures. Though depending on the conditions you can get other products like diethyl ether,
ethylsulfuric acid, and diethyl sulfate. |
That's interesting - so, is there a way to reliably make just or mainly Diethyl Ether using Ethanol and H2SO4? |
Wikipedia says ethanol and H2SO4 can make diethyl ether when heated between 140 C and 170 C. https://en.wikipedia.org/wiki/Ethyl_sulfate#Production
Nile red also has a video on making diethyl ether from ethanol. https://www.youtube.com/watch?v=6Z2oE8-uthU
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G-Coupled
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Cool, thanks. 
Ether's one of those oh-so-handy reagents that a lot of people find harder to obtain - being able to make it from two far more OTC ingredients is very
useful to know about.
[Edited on 15-12-2019 by G-Coupled]
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Cou
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| Quote: Originally posted by G-Coupled | Cool, thanks.
Ether's one of those oh-so-handy reagents that a lot of people find harder to obtain - being able to make it from two far more OTC ingredients is very
useful to know about.
[Edited on 15-12-2019 by G-Coupled] |
There's also a lot of side reactions to deal with. formation of ethene and ethyl sulfate. www.elementalscientific.net stopped selling it (probably due to inhalant abuse), and there are some expensive listings on ebay.
I haven't done a cost analysis yet, but it could be cheaper or about the same price to distill it from this stuff: https://www.amazon.com/Gunk-Liquid-Starting-Fluid-M3911/dp/B...
MSDS https://www.winzer.com/UserFiles/documents/891_3052_7.pdf (they call it oxybis ethane to prevent abuse)
procedure https://www.youtube.com/watch?v=r8MwwpSWeq4
[Edited on 15-12-2019 by Cou]
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G-Coupled
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Hunh, I'd be more worried about desperados huffing Chloroform, they seem to still sell that.
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Cou
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Just finished reflux. 25 mL of isopropyl alcohol, 7.3 grams of salicylic acid, and 0.5 mL of sulfuric acid, refluxed for 1.5 hours. I poured it all
into a beaker to evaporate off some isopropyl alcohol, and isopropyl alcohol is so strong smelling that it overpowers any ester smell. Maybe i can
detect some greenish odor but not sure. No color change or gasoline smell. I'm a bit concerned that I didn't use enough sulfuric acid for catalysis.
now i'm waiting for evaporation, in a day or 2 I hope a layer forms. if not I will try again with more sulfuric acid
Do u guys think that was enough sulfuric acid? it's the same molar ratio that nurdrage used for ethyl propionate
[Edited on 15-12-2019 by Cou]
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Tsjerk
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| Quote: Originally posted by Cou | Just finished reflux. 25 mL of isopropyl alcohol, 7.3 grams of salicylic acid, and 0.5 mL of sulfuric acid, refluxed for 1.5 hours. I poured it all
into a beaker to evaporate off some isopropyl alcohol, and isopropyl alcohol is so strong smelling that it overpowers any ester smell. Maybe i can
detect some greenish odor but not sure. No color change or gasoline smell. I'm a bit concerned that I didn't use enough sulfuric acid for catalysis.
now i'm waiting for evaporation, in a day or 2 I hope a layer forms. if not I will try again with more sulfuric acid
Do u guys think that was enough sulfuric acid? it's the same molar ratio that nurdrage used for ethyl propionate
[Edited on 15-12-2019 by Cou] |
I think this is enough sulfuric acid (it is enough for sure, it is a catalyst) but it wouldn't hurt to leave it to react a little longer. It could
very well be the reaction is not finished yet. You don't have to react it at reflux temperature. I would run it at reflux for as long as you could
reflux it and then neutralize the acid before evaporating the solvent (isopropyl in this case).
The reason for neutralizing the acid before evaporating the alcohol is that you will get the same problem you got the last time when you concentrate
the reaction too much, even at room temperature.
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Cou
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Total volume of the reaction is about 25 mL. I added 25 mL saturated sodium bicarbonate and unfortunately no layer formed, but i definitely notice a
greenish vegetal/spinach kind of smell, smell distinct from isopropyl alcohol and consistent with reports of the odor of isopropyl salicylate on this
board. since the sulfuric acid is neutralized, i'm now hoping to get an ester layer by boiling off the water and isopropyl alcohol
[Edited on 15-12-2019 by Cou]
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Cou
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Sh*t my workup failed. Could not get any layers to form. I might try again with a 0.4 molar ratio of sulfuric acid
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Pumukli
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A few drops of sulfuric acid should be enough, with much longer reflux time (8-10 hours). (It works for i-propyl-benzoate, the yield is mediocre.)
I tried to find a synth. description of your target compound but failed. Both online and in my books. Maybe it's time to do a bit more serious
literature search.
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Amos
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I believe the gasoline odor is actually diisopropyl ether; I noticed a petrochemical-scented fraction coming over at quite a low temperature when I
tried to purify my isopropyl salicylate.
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