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chemplayer..
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KI in methanol and HCl. That's also very interesting and worth a try.
Does anyone think that plain old HI in aqueous solution (a strong one mind you) with a catalyst like ZnCl2 would work?
Yes, once you've got the equipment and reagents, finding ways to end up with vaguely pure products and even half-heartedly trying to confirm their
identity is to be honest >90% of the challenge. If it's something like (say) ethyl iodide where we can wash it with water and sodium bicarbonate,
then dry it completely, and can measure a rough density that is within about 5-10% then that's a good enough confirmation for us and we'll then try
the product out in a subsequent reaction to see if it behaves as expected. Normally we find that the best test is trying out a subsequent reaction.
To us a crude yield is really a 'maximum yield'. It means 'hooray we got something that isn't an obviously impure sludge, and it seems to match what
the procedure said we'd get or the high level expected characteristics'. Which frankly for us at this point anyway is a good enough success in itself.
We don't personally consider ourselves 'amateur scientists' or 'independent experimenters'. We just do reactions for fun and to learn as neither of us
are chemists and it's such an amazing and fascinating science. Obviously if your goals are different (e.g. a specific synthesis or genuine innovation)
then having a much more rigorous approach is necessary. To be fair it almost certainly adds to the enjoyment and satisfaction ultimately as well - but
we're still on the road to becoming that disciplined...
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blogfast25
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@chemplayer
Well, it's not too late do a capillary BP and a density on the EtI, unless it's been ditched of course.
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JJay
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I think HI would probably work even without a catalyst, but yields might not be the greatest that way.
I wish I had some HI. I could make some, but it is covered by all sorts of legal restrictions here.
Edit: I am too tired for the Internet right now. *yawn*
[Edited on 14-2-2016 by JJay]
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Amos
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Quote: Originally posted by JJay  | I think HI would probably work even without a catalyst, but yields might be the greatest that way.
I wish I had some HI. I could make some, but it is covered by all sorts of legal restrictions here. |
Make it and use it the same day, without storing it. There are a couple of youtube videos detailing its preparation.
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S.C. Wack
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The first discovery using aluminum was published in 1926, just ethyl iodide, and had an unexpected workup procedure that nonetheless led to 80% yield
they said. Then a Russian in 1941 included methyl iodide, no yield given in the abstract. Particularly interesting there is also a
70% yield of methyl iodide and phenol from anisole.
Norris illustrated ethyl iodide from HI and ethanol in Experimental Organic Chemistry, but did not mention substituting methanol. He did substitute it
years earlier though: 5.5 g methanol, 105 g. 57% HI, 21 g. methyl iodide.
For the methyl and ethyl iodides, it seems reasonable to assume that the washed and dried distillate from any preparation would be as pure as the
alcohol it came from.
There was an earlier post.
http://www.sciencemadness.org/talk/viewthread.php?tid=12394&...
BTW the higher solubility of the NaI here may be advantageous.
[Edited on 14-2-2016 by S.C. Wack]
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blogfast25
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| Quote: Originally posted by S.C. Wack | | The first discovery using aluminum was published in 1926, just ethyl iodide, and had an unexpected workup procedure that nonetheless led to 80% yield
they said. |
Yes, this related patent mentions it:
| Quote: | | In two works, Jones and Green, J. Chem. Soc. 1926, 270; J. Chem. Soc. 1927, 928, report the reaction of aluminum with three atoms of iodine, with
hydrolysis of the aluminum tri-iodide in the presence of an alcohol and water to produce the corresponding alkyl iodide. These Workers state aluminum
can advantageously be used instead of phosphorus in the synthesis. |
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AJKOER
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Thought of an interesting path based on CH4 (and not CH3OH), HCl to produce Cl2 from say NaOCl, NaI, acetone and sunlight to create an impure CH3I.
First, perform a photolysis of CH4 in excess and Cl2 to create some CH3Cl and other products.See, for example, reaction summary and discussion at http://www.chemguide.co.uk/mechanisms/freerad/multisubcl.htm... . Or, one can repeat the path first used to synthesized by the French chemists
Jean-Baptiste Dumas and Eugene Peligot in 1835 from boiling a mixture of methanol, sulfuric acid, and sodium chloride. Source: https://en.m.wikipedia.org/wiki/Chloromethane .
Second, dissolve separately the NaI and any formed CH3Cl (as a gas and other impurities) both in acetone. Combine solutions and let the NaCl
precipitate out. Source to quote from Wikipedia (https://en.m.wikipedia.org/wiki/Iodine ):
"Sodium iodide is especially useful in the Finkelstein reaction, because it is soluble in acetone, whereas potassium iodide is less so. In this
reaction, an alkyl chloride is converted to an alkyl iodide. This relies on the insolubility of sodium chloride in acetone to drive the reaction:
R-Cl (acetone) + NaI (acetone) → R-I (acetone) + NaCl (s)"
[Edited on 19-2-2016 by AJKOER]
[Edited on 19-2-2016 by AJKOER]
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blogfast25
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@AJ:
You are aware that the BP of CH3Cl is about - 24 C, right?
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AJKOER
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Thanks Blogfast for the comment.
I have since edited my thread to be clear that one is to dissolve the gaseous CH3Cl in acetone.
[Edit] The bottom line of my suggested route is that if you has a good workable path to CH3Cl, then via NaI and acetone, one may be able to produce
CH3I as well.
[Edited on 19-2-2016 by AJKOER]
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blogfast25
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| Quote: Originally posted by AJKOER |
I have since edited my thread to be clear that one is to dissolve the gaseous CH3Cl in acetone.
[Edit] The bottom line of my suggested route is that if you has a good workable path to CH3Cl, then via NaI and acetone, one may be able to produce
CH3I as well.
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The preparation of CH3Cl from methanol, NaCl and conc. H2SO4 should be unproblematic.
But you can't prepare a solution of CH3Cl in acetone without pressure to keep the CH3Cl in there. Not with such a low BP.
One possibility would be to gas a solution of NaI in acetone with CH3Cl but that's not really for the faint of heart either...
[Edited on 19-2-2016 by blogfast25]
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Nicodem
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A lot of talk instead of doing an experiment. Like this:
To NaI (18.8 g, 125 mmol) was added methanol (8 g, 250 mmol, 2 eq.) and 37% hydrochloric acid (42 mL, 500 mmol, 4 eq.). There was a slight exotherm.
The yellow suspension was left standing stoppered at room temperature. The next day there was a brown liquid present bellow the precipitated salts.
After standing for one week, the salts were dissolved by adding water (40 mL) and the aqueous phase decanted. The heavy red liquid product was washed
with a solution of ascorbic acid (0.2 g) in water (40 mL) and separated to give a colorless liquid (9.95 g, 56%): density 2.30 g/mL (+/- 0.15 g/mL);
bp 43 °C.
…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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blogfast25
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| Quote: Originally posted by Nicodem |
To NaI (18.8 g, 125 mmol) was added methanol (8 g, 250 mmol, 2 eq.) and 37% hydrochloric acid (42 mL, 500 mmol, 4 eq.). There was a slight exotherm.
The yellow suspension was left standing stoppered at room temperature. The next day there was a brown liquid present bellow the precipitated salts.
After standing for one week, the salts were dissolved by adding water (40 mL) and the aqueous phase decanted. The heavy red liquid product was washed
with a solution of ascorbic acid (0.2 g) in water (40 mL) and separated to give a colorless liquid (9.95 g, 56%): density 2.30 g/mL (+/- 0.15 g/mL);
bp 43 °C. |
Hmmm... works rather well.
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DJF90
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| Quote: Originally posted by Nicodem | A lot of talk instead of doing an experiment. Like this:
To NaI (18.8 g, 125 mmol) was added methanol (8 g, 250 mmol, 2 eq.) and 37% hydrochloric acid (42 mL, 500 mmol, 4 eq.). There was a slight exotherm.
The yellow suspension was left standing stoppered at room temperature. The next day there was a brown liquid present bellow the precipitated salts.
After standing for one week, the salts were dissolved by adding water (40 mL) and the aqueous phase decanted. The heavy red liquid product was washed
with a solution of ascorbic acid (0.2 g) in water (40 mL) and separated to give a colorless liquid (9.95 g, 56%): density 2.30 g/mL (+/- 0.15 g/mL);
bp 43 °C. |
Well done for taking the time and initiative to give it a go Nicodem. Its a pretty nice result although I have a question... Is there a rationale
behind how you conducted the experiment (molar equivalents, lack of stirring and heating)?
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Nicodem
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| Quote: Originally posted by DJF90 | | Is there a rationale behind how you conducted the experiment (molar equivalents, lack of stirring and heating)? |
There is no reaction related rationale for lack of stirring. It's just that I'm flooded with work and could not afford to occupy a stirrer for that
long. You can see the motivation as one of those moments: "Why the f***k do we have members that ask questions that can be answered so easily by a
ridiculously simple experiment?"
Heating would be pointless. I would need to set up a reflux (occupying a stirrer), and with the bp of the product, the highest achievable temperature
would not be particularly helpful. Containing MeI for long enough with normal cooling water would be hard on such a small scale. Just stoppering the
reaction can be a compromise between reaction time and simplicity.
Molar equivalents? You don't expect me to do a DoE model on this? Except for having NaI as the limiting reagent, the rest was an arbitrary/intuitive
choice.
…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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DJF90
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I figured that might be the case.
| Quote: Originally posted by Nicodem |
Heating would be pointless. I would need to set up a reflux (occupying a stirrer), and with the bp of the product, the highest achievable temperature
would not be particularly helpful.
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I was just wondering what made you deviate from the procedure used with phosphoric acid (reactive distillation). You've answered that clearly, thanks.
| Quote: Originally posted by Nicodem |
Molar equivalents? You don't expect me to do a DoE model on this? Except for having NaI as the limiting reagent, the rest was an arbitrary/intuitive
choice.
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I didn't expect you to do anything, although I'm glad that you gave it a go. I suspected they were just educated choices.
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dicyanin
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My apologies for waking up the dead, but I thought I might as well share my own notes here using a variation of the methylsulfuric acid process (using
methanol as solvent instead of water, and NaI instead of KI).
Preparation of methyl iodide:
A solution of methylsulfuric acid is made by adding 50g concentrated sulfuric acid (pre-ban drain cleaner ~92%) dropwise with stirring to 25ml
(0.6mol) methanol in a cold-water bath.
In a 500ml flask equipped with magnetic stirrer and prepared for distillation, 45g (.60mol) of sodium iodide is dissolved in 70ml methanol. This is
stirred in a distillation setup fitted with a Claisen adapter and a separatory funnel, until the full dissolution of the NaI (lightyellow tinge of the
solution), and then heated on an oil bath until the bath temperature measures between 80-85*C. To this solution, methylsulfuric acid is added dropwise
via an addition funnel, and the methyl iodide distills almost immediately. The bath temperature is brought to 90°C towards the end of the addition.
A precipitate of Na2SO4 is formed, the mixture turns darker. (As sodium bisulfate cannot exist in alcoholic media, it decomposes
on forming into sodium sulfate and sulfuric acid. The Na2SO4 precipitates from solution and drives the reaction forward). The
product distilling over turns milky sometimes.
After about three hours, no more methyl iodide was seen to distill. The receiving flask contained 50ml of brine (saturated NaCl solution), cooled by
an ice/water bath. Methyl iodide forms the lower layer, the first thing that catches the eye is its high refractive index (for which it has some uses
in microscopy). The layers are separated and the MeI is dried over CaCl2. Yield: 21.7g (51%)
Results are somewhat worse than the procedure that uses water as solvent, it seems that there is no way to suppress partial oxidation to iodine using
sulfuric acid/methylsulfuric acid.
Recovery of iodine:
200ml water is added to the distilling flask and the mixture is stirred until all precipitated sodium sulfate has dissolved. The whole is transferred
to a 1L beaker and with good stirring 300ml 3% H2O2 is added. The mixture turned from an oily purplish to darkbrown and a
precipitate formed. Stirring was discontinued and the mixture allowed to stand for an hour.
When the dark precipitate of iodine has settled, the supernatant layer was decanted off, the slurry of iodine filtrated and washed with several
portions of ice-cold distilled water. The filter-cake was pressed to remove as much moisture as possible, then dried over CaCl2. The
amount of iodine recovered was 9.9 grams.
sic transit gloria mundi
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Boffis
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No apology needed for waking the dead! Nice experiment and fairly succesful. The slightly lower yield that Nicodem's experiment with HCl is probably
not significant. Interestingly, I have often found that if conc sulphuric acid is too oxidizing (eg when preparing alkyl bromides from alcohols with
NaBr and sulphuric acid) the problem can often be reduced by diluting the sulphuric acid to <85%. This shouldn't greatly affect things if Nicodem
can get away with 37% HCl solution so you may be able to get away with an even lower concentration.
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