Author Topic: A funny happening (a MeI generation experiment)  (Read 1690 times)

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Antoncho

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A funny happening (a MeI generation experiment)
« on: April 21, 2002, 03:53:00 PM »
Today something so extremely funny happened in SWIM's bedroom that he and his family are still in tears - so hard they laughed ::) .

Please, read it till the end - HELP needed - and i promise i'll bee as laconic as possible.

A brief preface - ChemTrip of HyperLab reported only 30% yield in an attempt to make MeI via KI/H3PO4 in methanol. Considering that SWIM's own attempt to make MeBr as described in .../nitroalkane.html for ethyl bromide produced a yield even more miserable, and to make MeCl - nothing at all, it was concluded that MeOH was significantly less basic than higher alcohols and generally unsuitable for such preparations. Of course, the classical way (with red P) was out of question.



So...


40 ml MeOH + 2,3 gr (double xcess) tech. Al grit + 12,5 g I2 in a 100 ml flask ------> the rxn is vigorous, spit into the condenser, but was easily subdued by immersion into ice water. The mixtr turns greenish, then colorless, w/black solids (probably Si from aluminium) and changes consistency to almost a gel, esp. when cooled. It was hoped that AlI3 would methanolyse to Al(OH)3 and MeI, but that didn't happen, at least at RT.

The mixtr sat in the freezer for 2 days - SWIM had no time for chemistry.

Then 10,2 ml approx. 82% HMeSO4 (the rest MeOH - made from 50 ml MEOH + 50 ml 92% H2SO4 + 24 g Na2SO4) was chilled and added in.

SWIM hoped that the rxn would go as follows:

4 Al + 3 I2 + 6HMeSO4 ----> 6MeI + 2Al2(SO4)3 + 3 H2

But....................................... :o


As soon as gentle heating under reflux was started, at ~55 C bath temp , drops of MeI quickly dripping from the condenser beecame apparent - as well as a pronounced production of H2S!!!.

Reflux was continued for as long as 2 hrs, then SWIM decided he'd had it. He distilled of all that distilled beelow 55 C - about 1,5 mls :(  - and, note - it was his utter impression that there was significantly more MeI in the mixture in the beginning (judging by reflux/distillation rate).

The stench of H2S was still very bad, no matter how efficient swim's draught was, so he decided to pour some alkali into the mixtr bee4 throwing it away. But when he did it -  :o  ::)  ;D  :o  :o  :o  - the mixtr began to bubble (duh...) and an incredibly foul stench developed so quickly that bee4 SWIM flushed it down the drain the whole apartment stinked so badly that... uh.... well, you know.

The smell really lingers.

So... could anyone tell him what the fuck happened??? Antoncho is not asking what to do - just how come there was a production of hydrogene sulfide??  What is the possible mechanism beehind that and how that can bee avoided???

Also - what, would you suggest that smell was? (Well, Antoncho guesses it can bee nothing else than dimethylsulfide, right? Formed from H2S and MeI, right?)




Antoncho

foxy2

  • Guest
Water is the problem
« Reply #1 on: April 21, 2002, 04:33:00 PM »
Hydroiodic acid reduced some of the sulfate to H2S.

You had a brew of AlI3 and probably some MeI in methanol.  When you Then 10,2 ml approx. 82% HMeSO4 (the rest MeOH - made from 50 ml MEOH + 50 ml 92% H2SO4 + 24 g Na2SO4) was chilled and added in.

The residual water from the 92% H2SO4 reacted with AlI3 to form HI, which reduced some Sulfate to H2S.  H2S is SUPER stinky so even a few ppm will create quite a mess.

Not sure but you assumption that methylsulfide formed when you added base is definately possible.
Just my guess :)
Foxy, Wishing you a stink free week  ;)

Those who give up essential liberties for temporary safety deserve neither liberty nor safety

poix

  • Guest
sulfur stink
« Reply #2 on: April 21, 2002, 04:54:00 PM »

When swim was toying with 2ct2 synthesis with ethanethiol and 2,5dmb there was also stinky odor, all my neighbors had smell it and I'm not allowed to repeat this experiment now. Hopefully I'm in good relation w/ my neighbors and they didnt call the cops.

Anyway I have reference to generate MeI with KI and H2SO4/MeOH in 90% yield (Czech patent) or from iodine in AcOMe with Al and AcOH (65% calculated on Iodine).

I can dig up if someone want. (but I haven't the full text)


Antoncho

  • Guest
!!!!!!!!!!!!!!!!!!!!
« Reply #3 on: April 21, 2002, 05:21:00 PM »

Anyway I have reference to generate MeI with KI and H2SO4/MeOH in 90% yield (Czech patent) or from iodine in AcOMe with Al and AcOH (65% calculated on Iodine).

I can dig up if someone want. (but I haven't the full text)





YES! YES! PLEASE, DO!!

If that Czech patent can bee found on EspaceNet, then....... Translation isn't a problem, AFAIK.

Pleasse, find those refs!!


Antoncho


Antoncho

  • Guest
The disussion of possible mechanism...
« Reply #4 on: April 21, 2002, 06:04:00 PM »
2 Foxy: with all my respect to your opinion, friend, i disagree with what you said.

First, all water should have been removed from the HMeSO4, beecause even taking in account the 8% by weight contained in the H2SO4, still Na2SO4 was taken roughly in 35% xcess, and it was very finely coffee-ground. Of course, that is not a guarantee - but the same proportions worked fine in SWIM's experiments w/NaMeSO4 and related.

Then. Are you saying that HI will reduce H2SO4 all the way to H2S?? i find it highly improbable, beecause it is a known fact that H2S reduces iodine to HI, does it not? To me it looks more like the reducing species here is aluminium, or maybee (and even probably) H2SO4 is first reduced to sulfur (BTW, some of it was apparent in the 1st stage of the rxn) and the latter reacts w/aluminium and decomposes to H2S instantly.

OK.... SWIM thought he'd use a 2x xcess of Al to neutralize sulfuric acid that is supposed to bee formed upon the rxn of HI w/MeOH - but now he sees that a totally different rxn equasion is possible...

The next time he'll try it w/an equimolar Al qtty.

IF the other, sexier route - via that Czech patent - doesn't beecome known to him[excited][excited][excited]


Antoncho

foxy2

  • Guest
well
« Reply #5 on: April 21, 2002, 06:13:00 PM »
Is there any other possible reducing agent?
The aluminum, I guess, but that doesn't happen commonly so I still think its then due to small amounts of water forming HI.

Check this

Post 299818

(foxy2: "MeI and alkyl iodide synthesis", Chemistry Discourse)

;)


Those who give up essential liberties for temporary safety deserve neither liberty nor safety