Sciencemadness Discussion Board

Methyl Iodide Synthesis ?

einstein(not) - 27-1-2007 at 16:12

This is my first post so please pardon any unintend breech of forum etiquite.
Due to the unavailablity of phosphorus I've been considering this potential synthesis of methyl iodide and would appreciate input.

If a mixture of equal parts methanol,water and iodine were bubbled with hydrogen sulfide gas would methyl iodide be produced ?

Would it be recoverable from any other products produced ?

PainKilla - 27-1-2007 at 16:32

Even though the are already threads for this (i.e., UTSFE next time):

This is from The Hive - MeI methods

Quote: Antoncho - (Official Hive Translator) - 04-26-02 15:25 - No 301629
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Two tried-and-true ways to make MeI !
(Rated as: excellent) Bookmark

Recently, two bright and enthusiastic Russian hallucinations - namely, Someone-Who-Isn't-Vitsh and Someone-Who-Isn't-Antoncho, decided to undertake a quest to find some properly working pathways to methyl iodide, a much needed reagent in the field of kitchen synthesis, or Young Chemistry, as it is proudly known at HyperLabsmile.

And - lo and beehold! - both of them hallucinations succeeded, thus having developed two different tried-and-true ways of synthesizing this substance from completely OTC ingredients.

Here goes:

SWIVitsh:

To 40 g iodine there was added 50 mls MeOH and 3,2 g Al foil in small balls. The mixtr is warmed up a bit until the rxn starts and immersed into cold waterbath as needed to control the rxn.
After the rxn is finished, there's added a mixtr of 30 ml aqua and 20 ml H2SO4, pre-chilled in a freezer. The addition was planned to bee done drop-by-drop w/stirring, but the mixtr thickened so much that 20 more mls MeOH had to bee added and the addition of the acid further carried in portions.
After all was added and well mixed, distilliation of MeI is begun, with the end of the condenser immersed into cold water. At 1st some H2S is emitted and the water in the receiver gets milky.
When all of the product has been distilled, the water in the receiver is saturated w/NaCl and the product is pulled out w/a syringe.

Yield of the crude MeI is 55%.
Sidenote: should bee much better with usage of H3PO4, don't you think so? It would react w/AlI3 quantitatively w/out any oxidation!

SWIAntoncho:

36,6 g potassium iodide and 20 mls water are placed into a 100 ml FBF and plugged w/a 2-hole stopper.

One hole of the stopper is fitted w/a distillation condenser (end immersed into a beaker w/cold water) and into the other is stuck a plastic syringe (SWIA doesn't have a pressure-equalized addition funnel of such size) with 20ml ~82% HMeSO4 (made from 50mls MeOH, 50 mls H2SO4, 24 g Na2SO4).

The mixture is heated on a waterbath to 80-90 C, KI dissolves and addition of the acid is commenced. The mxtr immediately turns dark brown and some H2S is given off. However, it very soon stops and oily drops of MeI appear in the condenser.

The addition was carried for ~5 hrs (SWIM was particularly sloppy that time, adding acid irregularly, at the end sayin 'fuqit' and going to bed - at 4am in the morning), and the theoretically calculated qtty of the acid wasn't enough - total of ~35-45 mls was added. SWIM is certain though, w/the use of an addition funnel, it would take much less time.

Addition of each new portion of acid (usually followed by shaking the flasksmile - OTC mag stirrer, so to saysmile) caused a very visible increase in MeI production, however near the end that effect ceased, and purple vapors began to appear. The distillation was stopped when separation of MeI (and SWIA's patience) almost ceased (however, in the morning there was ~0,3-0,4 mls of the black product under the layer of solidified salt, which SWIA didn't bother to extract).

The yield of the crude product was 10,5 mls, which equals to 77% of theory.

Two sidenotes:

1) Naturally, SWIA was surprised out of his mind to see the reaction WORK! From theoretical viewpoint it was simply inconceivable, but nevertheless - real!
On spending some time in pondering over this obvious cognitive dissonance, though, he arrived at a reasonable explanation:
KI and iodine, initially formed in situ, produce a triiodide ion. The latter, being a much stronger oxidant than mere iodine, forms an equilibrium with sulfuric acid, re-oxidating it back to SO4++, once it's reduced by 'simple' iodide ions, which still are prevalent in the solution. HI is formed as a result of reaction between I3- and H2S.
Which leads us to some further conclusions.

2) It was noted that when too large a portion of HMeSO4 was added at once, some gas was generated - probably, H2S. It is SWIA's deep conviction that a higher yield may bee easily achieved if proper stirring and an addition funnel are emloyed. The 90% yield stated in the original patent is, in his humble opinion, a reasonably practical figure.
Adding I2 to the soln and pre-forming KI3 bee4ahand might bee a good idea, too.

Antoncho wants, on SWIA's beehalf, thank very much his comrade bees - Foxy2 and Poix for bringing this excellent procedure to his attention!

Antoncho
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and
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Antoncho - (Official Hive Translator) - 07-12-02 09:43 - No 331620
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Another trial. Bookmark

95g ammonium iodide were dissolved in min qtty of hot water (heating it on waterbath as dissolution is very endotermic) and warmed to ~80C on waterbath.

To this soln 100ml of H2SO4/CH3OH (1:1 volume-wise) was added in portions of 5mls over 5 hours, distillate being collected under water. No stirring was employed xcept immediately after the addition of acid, when the flask was simply shaken by hand (a stirrer hotplate is something mythical for SWIMsmile). After the end of addition the rxn is held at 80C for 3 hrs, after which time almost no MeI distills over.

On contrast with employing KI as iodine source, there was no salt precipitation in the flask, which presumably had positive impact on yield.

The product after drying amounted to 35mls = 79,5g = 85% yield of theorycool.

Antoncho
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Please UTSFE next time...

einstein(not) - 27-1-2007 at 17:07

Thanks for the info. I had searched the forum prior to posting for this specific route. I didn't find a dedicated methyl iodide thread. Sorry for my oversight.

I am aware there are many ways to methyl iodide that don't require phosphorus. The availability of which was simply the reason I began thinking about this route to begin with. I apoligize for not making that clear.

I am still curious as to whether or not this is a possible route. In particular I am wondering whether or not water would even be required? Could the action of H2S on methanol and iodine alone produce MeI or would water be needed to produce hydroiodic acid in situ?

Interesting way to make Sulfuric Acid and Methyl Iodide

AndersHoveland - 15-2-2012 at 07:14

I have found some interesting reference to the reaction of methyl alcohol with sulfur dioxide and iodine to form sulfuric acid and methyl iodide.

This reaction could potentially be very useful to prepare alkyl iodides from their alcohols, and would be an interesting way to make sulfuric acid.

Unfortunately, I cannot find much information about this reaction.

Supposedly sulfur dioxide and iodine can be reacted with methanol to form sulfuric acid and methyl iodide, which separate into two separate liquid layers.
Dokiya, Kameyama, Fukuda (1979)
Quote:

A solution of iodine in methyl alcohol was treated with hydrogen sulphide until the deep brown color of the liquid has entirely disappeared. The presence of methyl iodie was proved by fractional distillation.

A solution of iodine in methyl alcohol was treated with sulphur dioxide. Here also methyl iodide was formed in small quantity. The main product consisted of different ethers.
Journal American Chemical Society; 4, 295 (year 1891)
Volume 13



Alkyl iodides are useful because the iodine atom is a good leaving group and can be easily substituted with other groups. So may be a route to making nitromethane or nitroethane from methanol or ethyl alcohol, for example.

WARNING: methyl iodide is a poisonous alkylating agent

Typically, only dilute sulfuric acid can be made by oxidizing SO2 with iodine water, because more concentrated H2SO4 oxidizes iodine ions. But the use of pure alcohol might allow more concentrated H2SO4 to form, since the CH3I that would form is likely less vulnerable to oxidation.

[Edited on 15-2-2012 by AndersHoveland]

blogfast25 - 15-2-2012 at 07:30

Which part of:

"Here also methyl iodide was formed in small quantity. The main product consisted of different ethers."

... didn't you understand?

ScienceSquirrel - 15-2-2012 at 07:54

There is a big difference between a reaction that may give trace amounts of something and a practical method of making it.
I suspect that at best this will produce a mixture from which a small amount of methyl iodide may be extractable after a lot of work.

neptunium - 15-2-2012 at 08:44

this has been done succesufuly before but when we dont have red phosphore or phosphoric acid its a way to get small yield of CH3I ...

ScienceSquirrel - 15-2-2012 at 09:41

Quote: Originally posted by neptunium  
this has been done succesufuly before but when we dont have red phosphore or phosphoric acid its a way to get small yield of CH3I ...


Does anyone have a reference or a documented preparation?

neptunium - 15-2-2012 at 13:47

sure,

http://www.sciencemadness.org/talk/viewthread.php?tid=7570#p...

ScienceSquirrel - 15-2-2012 at 15:42

Thanks Neptunium,
I have merged this into the older thread. The methods are prior to Anders Hoveland's post.


... and moved it to organic chemistry

[Edited on 15-2-2012 by ScienceSquirrel]

neptunium - 15-2-2012 at 16:57

no problem, i knew i saw it somewhere..

Endimion17 - 19-2-2012 at 07:51

I distinctly remember that unnerving chill of fear when long time ago I found out that methyl iodide can be used for making dimethylmercury. I still wonder why there are no reports of such accidents. It's fairly easy to make it, and to accidentally poison yourself is a piece of cake, as the product separation isn't needed at all, and skin/inhalation hazard is extremely severe.
One of the worst and scariest poisons out there is remarkably easy to obtain.

Ephoton - 19-2-2012 at 18:57

I personaly like SWIvitish's method :)

some drain cleaner and some aluminium foil is not hard to come by.

Though the idea of making hydrogen sulfide as a by product is a little scary for a newbee.
I love that first reply a quote from the hyperlab boys/girls :)

Ye thats some scarey stuff there Endimion
http://www.nejm.org/doi/full/10.1056/NEJM199806043382305

You do know were mad as a hatter comes from ?

mercury was used to harden hats and a hatter was subject to this compound all the time.

Another poison I have suffered from (both lead and mercury)

Made me very very tired and weak for a long time.
I have been told that dure in the period of time I was rather nasty to other people as well.

It is sometimes hard to see the changes that chemicals do to your personality your self and you
need second opinions to be sure.

Of course my poisoning was rather mild (It took a lot longer for the tests to come threw than I thought
it would too) and was not of the organomercury kind.

I would hate to go anywere near dimethylmercury with out some serious equipment to keep me safe.

neptunium - 20-2-2012 at 09:16

yeah that stuff (dimethyl mercury) is very nasty and unlike H2S doesnt smell bad at all..
i wonder how much more dangerous it is compare to HCN ? or a regular nerve agent? i beleive (CH3)2Hg is consider a nerve agent right?

Endimion17 - 20-2-2012 at 09:56

No, it's not a nerve agent because it acts extremely slow. For something to be called a nerve agent, it has to incapacitate quickly, on the order of minutes, in small quantities delivered by aerosol or vapor.

Yeah, it's scary stuff nonetheless. There's no way I'd ever try to synthesize something like dimethylmercury or nerve agent or any kind. I prefer to stay reasonably healthy as long as I can.

neptunium - 20-2-2012 at 17:27

i stand corrected...it is a neurotoxine wich is different indeed.

wikipedia has an article about this chemist who died from just a few drops on her hand a couple of months after exposure.
scarry shit.!

Endimion17 - 20-2-2012 at 17:42

Yes, Karen Wetterhahn. Ephoton's link describes her sickness quite well, and there are even more detailed reports on the Web. She died in a horrific death. Poor woman.

Xellos - 6-3-2012 at 06:15

Today, I did the ethyl iodide synthesis, H3PO4 way (more info: http://www.erowid.org/archive/rhodium/chemistry/tcboe/chapte... I used 1/10th amounts of everything, and refluxed for 2 hrs.). It worked perfectly... well, I didn't separate all the product, but the yield seems to be quite high. And it's executable in a common school lab (guess where I did it :D).
You can try an analogic reaction with methanol - but be careful, methyl iodide is much more volatile (it boils at ~45°C) and more harmful, so make sure to do as much as you can in ice, and you'd better wear sth. to protect yourself from possible fumes.

CaptainOfSmug - 28-3-2013 at 20:40

Sorry for reviving an old thread here.

I recently performed this experiment on a much smaller scale. After distillation of my final product using the procedure posted above using KI the distillate began as an almost milky white product but the after maybe 20 minutes it turned yellow. After a quick google search (I wasn't exactly sure what to search for other than methyl iodide impurities which I'm sure is vague) all I came across was that a free radical is present. Has this happened to anyone else or could I have just messed up when making the methanol, sulfuric acid, Na2SO4 mixture?