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not_important
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Soda siphons are filled to 100 to 130 psi, but are not meant to be heated. You'd do better making a metal shell to take the pressure, and placing a
glass container inside it to hold the reaction mix.
However note that this reaction can be done in a flow reactor using K2CO3 coated with PEG as the catalyst and reaction phase, and the reactants as
gas. The process can be run at atmospheric pressure. I suspect a mixed phase batch reaction, with DMC in the gas phase and the other reactant as
liquid, could also be done.
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garage chemist
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It would be nice if this thread can be reserved for DMS synthesis discussion.
Maybe you could open a "Green methylating agents" thread to discuss things like dimethyl carbonate, methyl tosylate, methyl mesylate etc...
Just a suggestion.
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franklyn
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Some old bones
http://www.sciencemadness.org/talk/viewthread.php?tid=1113&a...
Attachment: pat3024263.pdf (256kB)
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Fleaker
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I did a quick and dirty attempt in the lab the other day using 20% oleum and methanol. I also tried the bisulfate+MeOH to get the sodium methyl salt.
I just used a small amount, excess oleum, and about 2 mL of MeOH. I did it in a long Pyrex test tube immersed in cool water. Upon adding the first
half of the MeOH, there was a strong exotherm when the tube was put against my gloved hand. Measuring the temperature with a probe said it was 64*C,
and this was after I had removed it from the cool water! This is highly exothermic and produces a lot of vapor, most likely H2SO4 droplets. I let the
rest of the reaction mix cool down to 18C and added more MeOH and it went up to 59*C, but there was much less vapor produced. I added the alcohol
using a pasteur pipet.
There were two layers formed, the bottom sulfuric acid layer, and the oily top layer which did not wet glass. I have not had a chance to do any formal
qualitative testing on it, but I do not think it is methanol...
My reasoning is that I never saw any methanol condensing on the walls of the reaction tube. I used a tall test tube because I was expecting to see
MeOH condense on the walls but there was none, so I can only assume that it reacted to something much less volatile that MeOH. You would think that a
MeOH mixture would have some vapor pressure at 64*C, but there were no droplets on the walls of the test tube. I will probably run a larger batch and
see what I can get by rotovaping.
With the bisulfate method, I did not notice much indication of a reaction but rather saw methanol condensing. I heated it to about 50*C as the
reaction did not seem terribly exothermic by itself (very little measured temp difference). I do not think it works as well as the oleum method, where
there was definitely something happening.
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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Klute
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Thanks for sharing!!
It definatively looks like the oleum produced some DMS, so using Garagechemist's peroxodisulfate mehtod of making some oleum and reacting that with
MeOH could be the easiest method for producing small amounts of DMS. Plus oleum can be usefull for tons of other things.
I guess adding the oleum to excess MeOH would give less of an exothermic reaction, although adding oleum might be a bit less practical than the
other way around.
My To-do's list has just got bigger
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garage chemist
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You should try pouring the oleum/MeOH reaction mix into ice water and see if any oil settles to the bottom. Any oil would likely be crude DMS.
Again, I would be most interested in hearing about experiments with the H2SO4 method.
One could easily do that on a small scale: put 10g MeOH in a flask, carefully add 50ml conc H2SO4 with swirling and rapidly distill the mix over a
strong flame.
The distillate should then consist of two phases.
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Fleaker
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I think I already have DMS available, so I'm mainly just doing this to do it. I have no use for the methylating agent. I used oleum instead of trying
with sulfuric because I have plenty of oleum, and I was fairly certain I'd see something. I'll see what refluxing with conc. sulfuric does.
The ice water idea is a good one. I will try that.
As far as distilling the mix, I'm really prone to thinking that there will be no methanol present. It appeared to be a fairly complete reaction, but
it's all speculation...
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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Klute
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I'd equally be very interested to see how the atm distn goes!
At the risk of sounding a little selfish, I'm on dozens of other projects at the moment, chemical or not, and as I'm not in desperate need for
methylating agents, this reaction isn't a priority. Even if it can't be too long at the scale you suggest GC, doing long days of work, having a
minimum social life (my girlfriend isn't a chemistry fan, she's even jealous sometimes ) leaves very little time in the lab.
Again, thanks for sharing Fleaker, especially if you're not in the need of DMS. Considering the price of oleurm, i can only say this a very generous
experiment Thumbs up!
[Edited on 22-1-2008 by Klute]
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Nicodem
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| Quote: | Originally posted by garage chemist
You should try pouring the oleum/MeOH reaction mix into ice water and see if any oil settles to the bottom. Any oil would likely be crude DMS.
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I got the impression that dimethyl sulfate forms only during the distillation while at room temperature one would mostly have a mixture of methyl
sulfuric acid and H2SO4? Kind of like the thermolysis of sodium methylsulfate which gives dimethyl sulfate and Na2SO4. If dimethyl sulfate is indeed
the main ester in the mix already at room temperature, then it could potentially be extracted with CH2Cl2 with which H2SO4 is immiscible. Washing the
combined extracts once with water should remove most of the methyl sulfuric acid and methanol traces, leaving only dimethyl sulfate.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
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Fleaker
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Excellent idea as usual Nicodem. A rotary evaporator would make short work of the DCM solvent.
How hot must it be for the methyl sulfuric acid to convert completely to the ester?
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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PainKilla
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I've had mediocre results at synthesizing DMS. There has been extensive discussion of this topic at other forums and so far what I've tried has only
lead me to one conclusion: vacuum distillation is the only really viable method.
- I've tried distilling from various methyl sulfuric acid salts, which according to an old Chem. Ber. reference (IIRC) are supposed to liberate DMS
upon warming, and especially so under vacuum. Nothing happened.
- I've tried distilling straight methanol/sulfuric under a few different conditions, using different proportions, and drying agents. This also has led
to mixed success (ranging from 10-20% or so, from what I remember)... under vacuum at least.
The method I have found works the best is attached.
A couple of notes:
I am sure that the methyl sulfuric acid formed has traces of sulfuric acid in it... I can't decant well enough to eliminate all traces of sodium
sulfate, so as a result water is inherently present during distillation. Additionally, I am not sure how well the patent actually does work to begin
with... but it does seems to work better than straight distillation, and given the cost of the materials, the relatively low yield of obtained
dimethyl sulfate is decent in that regard.
The dimethyl sulfate obtained works well for further reactions, though care should be taken to fully neutralize it as some decomposition was noted
after a few months of storage at room temperature in a sealed vial (stored over anhydrous magnesium sulfate). I don't know what happened here... in
any case, just a forewarning if you plan on storing this for an extended period of time.
Attachment: Dimethyl Sulfate Synthesis.rtf (4kB)
This file has been downloaded 4566 times
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Klute
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Thanks for that very well written document Painkilla! I take it the yield claimed is what you usualy obtained, and I think it is very reasonable,
owing, as you say, to the cheapness of the reactants and the usefullness of the product.
Concerning the distn, a few questions: did you use a short coluum? How marked is the transition from DMS and excess H2SO4? Was there any damadge to
the still flask?
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PainKilla
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I used regular 19/22 Pyrex glassware with a 200mm condensor; only one was needed. As far as the rest of the setup, I typically tried to shorten the
distance that the vapor must travel, as using larger flasks seemed to give a lesser yield. I don't know if this is a fault of my vacuum or a tendency
of the reaction.
I did do this specific reaction a few times (overall I've tried making DMS using various methods probably 20-25 times), as dimethyl sulfate was at one
point a reagent that was rather difficult for me to buy. The reaction is rather quick - it's possible to do within two hours, plus another hour for
setup/cleanup. The glassware used still survives to this day, no problems of any sort. In fact, the only time something did break, was indirectly
caused by the reaction: I stepped on a condensor. :*(
The transition is rather strange. When you initally mix the Na2SO4 and CH3HSO4, the Na2SO4 forms a hard solid in the bottom of the flask, which is why
it's important to added Na2SO4 to an already stirred mixture of CH3HSO4. After this, heat was applied (via an oil bath) and nothing seems to happen
until the temperature is about 70-80*C. At this point you can see an oily substance condensing, and it seems to co-condense with methanol or water -
makes no sense to me though, since they should both be quite gaseous at those pressures.
The distillation continues and the temperature raised until no more oily DMS condenses. A vapor begins to come off the reaction flask, I suppose it is
sulfuric acid vapors. In any case, it does not affect the distillation in any way. The Na2SO4 then seems to dissolve in the mixture - also an
interesting curiosity.
The liquid in the reciever is most interesting: it's oily in the condensor but upon looking at it during the first few minutes it's in the reciever,
it looks like regular water. Eventually, DMS oils out of it. The most interesting thing is, this liquid, does not get neutralized by water, and is
soluble in it. So it's not any sort of acid... and probably not methanol. But how can it be water?
In any case, the reaction is indeed cheap and great for making small, usable amounts of DMS.
Methyl iodide is easier to make and yields higher, but since you almost always need to use an excess of CH3I, the increased yield and volatility
really isn't worth it.
I should note I did this distillation outside with gloves and the like. (Although the reaction can be left unattended.)
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sonogashira
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PainKilla, did you not purify the methyl sulfuric acid other than by decanting it from the sodium sulfate? Could it be vacuum
distilled perhaps, or is it not necessary to purify it for use in the next step?
| Quote: | Originally posted by Nicodem
I wanted to say, that if dimethyl sulfate is needed for methylations of phenols, then one could consider the use of KOSO2OMe which is easily prepared
from OTC materials. I will dig out the reference for its use in phenol methylation if anyone is interested at all. |
Any chance of getting this reference Nicodem? I would be most interested
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PainKilla
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There are actually quite a few ways to make methyl sulfuric acid and/or it's salts, however, I only briefly explored the other routes, mainly it's
salts, simply because they involve much more work so as a result I took a liking to this simple and quick method that seems to largely work as
advertised.
The procedure I posted isn't meant to be high-yielding, it's rather just a simple and efficient way to get DMS. I've never needed large amounts of it
so there was never a reason to optimize the synthesis to yield especially well given the ease and price of the reagents.
I did try filtering the methyl sulfuric acid, it however tore my cellulose filter apart during filtration, so something more resistant would have to
be used.
If you distill methyl sulfuric you are just going to get dimethyl sulfate (albeit in lower yields).
There may be other ways to dry it, but this is the most commonly accessible. I would recommend a patent and literature search... There is a huge
amount of patent "literature" on the topic (though how much of that actually works in practice is unknown to me - it seems very few actually work),
and older books on chemistry almost always have some "unique" method of synthesized DMS.
Edit: I should not however, discourage anyone from retrying the experiments with methyl sulfuric acid salts, I suspect as there was some water (and
thus sulfuric acid) present in my CH3HSO4, the reaction would not have gone quite as advertised... that is:
2CH3HSO4 + Ba(OH)2 ---> (CH3)2Ba(SO4)2 + 2H2O... but:
H2SO4 + Ba(OH)2 --> BaSO4 + 2H2O
The second reaction would likely occur faster, and the water formed would serve to hydrolyze more acid... so I think you really need to have very,
very, dry methyl sulfuric for this to work to any appreciable degree.
The sodium salt however was made via different method:
CH3HSO4 + NaCl --> CH3NaSO4 + HCl
However this salt did not work as a DMS source, as advertised, under vacuum.
[Edited on 25-1-2008 by PainKilla]
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Klute
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So you distiled the MeHSO4 directly from the Na2SO4? That's surely were your water came from,a s it woill loose the water of hydration upon heating.
But I recall this method worked anyway, so maybe the Na2SO4 hold juste enough to the water for it not to hydrolyse the methyl sulfuric acid or the
DMS, especiially at those temperatures. Have you tried deacnting the MeHSO4 from the sulfate before distilling? This was brought up a few times too.
It's a pleasure to read such detailled descriptions. Makes it seem so easy
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PainKilla
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No, first you make the methyl sulfuric acid (at least, in a much more appreciable concentration), then decant from the (hydrated) sodium sulfate as
per the patent, then add Na2SO4 (just because it seems to help) and distill.
I have tried doing this with MgSO4 and the results were a bit worse.
[Edited on 25-1-2008 by PainKilla]
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Klute
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Sheesh, I've just realized you explained it explicitly in the document... Read it quickly last night, half didn't stay in .
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S.C. Wack
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Old news- the formation of DMS from H2SO4 and methanol was confirmed a long time ago in Compt. rend., and the same dudes also wrote of an interesting
lithium methyl sulfate pyrolysis. Both articles are on Gallica. Haven't tried the pyrolysis method yet even though I've got nothing better to do with
my LiCO3.
But I have tried the straight up 8-10 parts thing a few times (24/40, 19/22). I'd recommend a VERY short path distillation apparatus and the flask top
and head wrapped up good in something, because although it CAN be distilled at 760 mm., the problem is pot temperature (if like me you want to get
your product anytime soon). DMS high pot temp NO like. My yields sucked regardless.
Go vacuum.
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Klute
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Could you give the ref for these articles, if you've got them at hand obviously? I can translate them, they could be helpfull.
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Nicodem
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I think S. C. Wack is talking about the attached paper.
| Quote: | Originally posted by sonogashira
Any chance of getting this reference Nicodem? I would be most interested |
Well, one reference describing the methylation of plain phenol with MeOSO3H is the example 2 of patent US2490842. Also note the other examples where there is also described a methylation method for phenols that uses 1/2 equivalents of dimethyl
sulfate (both Me groups get transferred). The reaction temperature used is considerably higher than those in classical methylations with dimethyl
sulfate (that is: unlike those described in Vogel's or Organikum which work already at room temperature, but transfer only one Me group). This method
using MeOSO3H or 1/2 eq. (MeO)2SO2 is thus not suitable for those phenols which are unstable in basic media at 110-120°C.
This patented method was checked by Antoncho on hydroquinone and posted as post No 256342 on the late Hive forum. About 56% yield of
p-dimethoxybenzene was obtained, which is not bad considering the substrate and conditions used.
There is also at least one (but maybe more) reference(s) from literature using MeOSO3Na or MeOSO3K, but I can't find them at the moment (I will post
them as soon as I find them).
[Edited on 27/1/2008 by Nicodem]
Attachment: metal methylsulfates.pdf (153kB)
This file has been downloaded 869 times
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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S.C. Wack
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I uploaded the salt one before in another post here long ago IIRC. It's barium and strontium as well. The one using acid mentions getting a 44.4%
yield from 3 moles H2SO4 to 1 of methanol, which I was unable to obtain. I have a retort - which would have been the better apparatus, but I don't
trust the glassblower that much. Both are from 1919, in different volumes.
http://gallica.bnf.fr/ark:/12148/bpt6k3121p
page 1204.
http://gallica.bnf.fr/ark:/12148/bpt6k31220
page 655.
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Fleaker
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I tried this reaction again last night on a larger scale using 50 mL of MeOH and excess oleum.
The reaction is very exothermic, even with dripping in using an addition funnel. It is sputters and sprays when the funnel is open full tilt, I
believe this is because the MeOH penetrates the interface between the formed DMS and the heavier oleum.
Upon distillation with aspirator vacuum, the bulk of the product came over from 115-124*C, then a second portion at 180-188, the temperature just shot
up afterwards and I stopped the distillation. I wonder if I was distilling SO3 into my product!? In the reaction vessel, there was a good bit of
carbonization by the hot sulfuric acid.
About 75 mL of product collected in the receiving flask, but it was a bilayer: a clear, slight yellow bottom layer with a top layer floating above.
Both phases were quite mobile. I think there is a significant portion hydrogen methyl sulfate. I will try and take a GC/MS tomorrow evening.
I'm going to redistill the DMS over anhy. Na2SO4 with a little bit of oleum left.
I plan on trying this for diethyl sulfate by using chlorosulfonic acid sometime soon.
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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sonogashira
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| Quote: | Nicodem
This patented method was checked by Antoncho on hydroquinone and posted as post No 256342 on the late Hive forum. About 56% yield of
p-dimethoxybenzene was obtained, which is not bad considering the substrate and conditions used. |
I'm sorry to always be asking for assistance but i really have no idea where where i could find this "reference." I would be most interested if
someone could be of help
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Klute
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There you go:
Attachment: 000256342.html (55kB)
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