frogfot
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Iodoform
On my recent search for some easy experiment with iodine i found synthesis of iodoform. It required easy to get things..
Reactions:
CH3-CO-CH3 + I2 ==> CI3-CO-CH3 + 3HI
CI3-CO-CH3 + NaOH ==> CHI3 + CH3COONa
Preparation
4 g of KI are dissolved in 7,5 ml of destilled water and 2 g of I2 is added. 17,5 ml of water is added, followed by 5ml of acetone.
While stirring, a 10% solution of NaOH is dropped into reaction mixture from a dropping funnel until reddish color dissapears (approx. 4,5 ml).
Iodoform precipitates as yellow crystalls, those are filtered after 30 minutes, washed with small ammount of water and air dryed.
Yield is 0,93g (90%). In presence of light its hydrolised fast with strong bases, therefore excess of NaOH should be avoided.
Preparation was taken from "Practicum of organic chemistry" by S.S. Gitis, A. I. Glaz, A.V. Ivanov 1991
So, now I get to the point of this post, and point why I woke up 3:00 at the morning... Since I wanna survive the synthesis and after, happily sit and
observe the mysterious product behind tightly sealed glass jar, I wanna ask, how nasty is this stuff?
Heres MSDS of substance:
http://physchem.ox.ac.uk/MSDS/IO/iodoform.html
Heres its inhalation lethal concentration:
IHL-RAT LC50 165 ppm/7h
I wanned to carry out synthesis outside, then bring it in for quick vacuum filtration and after dry it outside and seal. Am I safe? or do I concern to
much?
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frogfot
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I guess I have to try this and see how it goes... treating it as gently as death.. 
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chemoleo
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Well, having made some iodoform recently, I have to say it's an extremely easy prep (the one above, only 3x the amount) - and upon NaOH addition
the red/brown colour of the KI/I2 disappears completely, leaving you with beautiful lemmon-yellow crystals. It looks like a dye, that's how
intensely yellow it is.
I checked some MSDS's, but it's not THAT toxic - it takes an adult about 80 g to ingest to die from it. Also it was used as an antiseptic. Inhalation is termed 'irritant'. On
that note, it's not just irritant, it is a frigging lachrymator! I was crying my eyes out when I poured the supernatant into the sink. Flushing
down the supernatant with lots of water seemed to help. I am not quite sure how to get this dry, considering this lachrymatory property. The smell,
other than that, is not very strong, just slightly of iodine - weird stuff.
On second thoughts - it looks like the properly washed iodoform is not as lachrymatory - instead this property was probably caused by intial reaction
products that were present in the supernatant - I imagine iodoacetone, a close relative to the well-known lachrymator chloroacetone, was formed as a
byproduct.
Also, the smell of acetaldehyde was there.
Further, it sticks to plastic (and glass somewhat) when in an aqueous suspension, and it forms a thin layer on top of water (surfactant properties). I
wouldn't recommend centrifugation therefore, filtration (fumehood or outside) is probably better.
It dissolves nicely in ethanol.
Anyway, it's a nice & easy prep.
[Edited on 22-12-2004 by chemoleo]
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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S.C. Wack
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It is wasteful of I (expensive here due to meth cooks) though. Of the 15 grams of I in, you poured 12.3 down the sink, using frogfot's reference
numbers 3X. Use of EtOH instead of acetone will keep you from flushing!
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chemoleo
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I know, it seems incredibly wasteful.
Why will ethanol be better though? I don't see how, the equation is still the same?
I figure the KI doesn't really participate in the reaction though, I think it's only there to solubilise the I2 in water (which it did).
Hmm... I think I should work out the reaction proper. Will be back on this.
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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S.C. Wack
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EtOH is better because there isn't any iodoacetone or other lachrymator being produced making you pour your stuff down the drain, so you can
recover your iodide. Acetaldehyde and ethyl alcohol are exceptions to the methyl ketone rule. Stepwise:
CH3CH2OH + KOI ->CH3CHO + KI + H2O
CH3CHO + 3 KOI -> CI3CHO + 3 KOH
CI3CHO + KOH -> CHI3 + HCOOK.
or
CH3COCH3 + 3 KOI -> CH3COCI3 + 3 KOH
CH3COCI3 + KOH -> CH3COOK + CHI3
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woelen
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I made iodoform in a way, which is somewhat less wasteful on (expensive) iodine and no elemental iodine is needed.
Dissolve some KI in water and add excess mix of H2O2(3%) and HCl(10%). This causes iodine to precipitate out of the liquid as a heavy and
compact precipitate which very quickly settles at the bottom. The liquid above it only remains light brown and recovering any iodine from this is not
worth the effort (it is less than 1% of the initial amount in the KI).
Decant the liquid carefully.
Add quite some water and shake. Hardly any iodine dissolves.
Within just a few seconds the iodine has settled again.
Decant the liquid carefully again and do another rinse with water.
Do a final decant and then add new water.
Also add some acetone, use an excess amount.
Now carefully add a concentrated solution of NaOH drop by drop and shake after each drop. Do this, until all brown/black iodine has disappeared.
You are left with a beautiful bright yellow precipitate, which can easily be filtered and rinsed with a little distilled water. Dry this at air in a
dark and (preferrably) warm place.
As you see, there is no need to work with dissolved iodine. The precipitate from the KI/H2O2/HCl liquid is sufficiently porous. In this way, you do
not flush away 2 out of three parts of iodine, but 1 out of 2 parts of iodine and you do not need I2, but the easier to obtain KI.
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Douchermann
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Is it neccesary to have the potassium Iodide for this reaction. Could I just sub in the ammount of elemental iodine that is in the KI (so about 5.3
grams of iodine total)? Or is it needed.
It\'s better to be pissed off than to be pissed on.
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woelen
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If you really want to use iodine instead of potassium iodide, then you can proceed as follows:
1) Dissolve all iodine in some acetone. For 5 grams of iodine I think that 10 ml of acetone will do.
2) Then add quite some water. Amount is not critical, a good starting point may be ten times the volume of acetone used. The iodine will precipitate
out as a heavy and coarse precipitate. The liquid above it is brown and consists of a small amount of iodine, dissolved in a water/acetone mix.
3) Next, add solution of NaOH dropwise, until no iodine can be seen anymore.
So, this method essentially is the same as mine, I just first transformed the iodide to iodine before making iodoform.
I, however, strongly prefer using potassium iodide, because that is MUCH easier to obtain and also quite a lot cheaper. I don't want to spoil my
precious iodine for a reaction, which also can be done with an iodide.
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FPMAGEL
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This is type of the same as above with different ratios.
Make a solution with 1g of potassium iodide in 5ml of water. Add iodine crystals to get a brown colour. Add 5ml of ethanol.Add some 10%NaOH solution
until the color disappears. Heat gently for two minutes. Allow to cool. The yellow precipitate is iodoform(CHI3)
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woelen
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What's the difference of this recipe with the ones, given at the start of this thread? Even the alcohol-variation is mentioned already.
The main difference between my recipe and the others is that no iodide is needed for keeping the iodine in solution. It works with a suspension of
iodine without dissolved iodide. This makes the process 33% more economic in terms of loosing iodine/iodide in the process. The cost of the process is
mainly determined by the iodine content, all other chems are dirt-cheap.
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peach
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<a href="http://img214.imageshack.us/i/img2333b.jpg/" target="_blank"><img src="http://img214.imageshack.us/img214/6159/img2333b.jpg"
alt="Free Image Hosting at www.ImageShack.us" border="0"/></a><br>
Health and physical properties
Oral, rabbit: LD50 = 450 mg/kg; oral, rat: LD50 = 355 mg/kg; Skin, rat: LD50 = 1184 mg/kg
Approximately 28g oral for adult male, or 90g skin exposure.
Comparative LD50's:
Aspirin, 200mg/kg, rat, oral
Caffeine, 192mg/kg, rat, oral
Not classified as carcinogenic, no teratogenic effect, but shows mutagenic activity in bacteria and yeast.
Molar mass: 393.73 g
Density: 4.008 g/cm3
Melting at: 123 °C
Boiling at: 217 °C (expl.)
The resource centre
Iodoform reaction example, Peter Keusch
A test to distinguish between ethanol and methanol, Practical Chemistry
Preparation of triiodomethane, Creative Chemistry
The Last American Frontier, page 240, Frederic L. Paxson
Not sure if this uploader is on the site, thanks for the English narration.
<iframe sandbox width="640" height="480" src="http://www.youtube.com/embed/XoG-suAkI68" frameborder="0" allowfullscreen></iframe>
Mewrox, making it.
<iframe sandbox width="640" height="360" src="http://www.youtube.com/embed/uXxIMa3sJDQ" frameborder="0" allowfullscreen></iframe>
And then breaking it. `.^P
<iframe sandbox width="640" height="360" src="http://www.youtube.com/embed/D7XIE3FVBSQ" frameborder="0" allowfullscreen></iframe>
---------------------------------------------------------
My experience of it
Having prepared some methyl iodide in the thread to which this link points, I thought I'd do iodoform next.
I tried two methods, one using woelens suggest above and the other using bleach (sodium hypochlorite).
The only one to hand was Domestos (the UK standard); 4.5g hypochlorite per 100ml. It was the toilet version, thick and gooy. I tried this method first
and, whilst it did work, boy o' boy did it take a long time! On adding the bleach, the iodoform readily formed. I
tried running it through a pair of coffee papers and it passed through as if they weren't even there. I put it all back in the beaker and decided to
let it settle before trying again, which took over 6 hours. The problems continued and I had to run the precipitate through the papers over and over
again, each time the paper gradually becoming more clogged and retaining more of the iodoform.
It took so long, I had more than enough time to wander off and try woelens suggestion of dissolving some iodine in acetone, adding water and then
base. Which was a good order of magnitude quicker. I had enough time, prior to that, to sublimate the iodine I had recovered from the methyl iodide
thread.
The precipitate from this second method filtered far, far more rapidly due to the larger particle size.
Having acquired iodoform from both, I set the filter papers out to dry, then scraped the combined results off. As my bleach was full of things other
than hypochlorite, and I wanted some pretty crystals to look at, I decided I'd go for recrystallisation (if you use the base method and aren't
bothered about the appearance of the results, no need to do this).
I found I was having difficulty getting the iodoform to dissolve in hot ethanol (which I have a very limited quantity of at the moment), so I swapped
to hot acetone for a filtration prior to recrystallising. As the material was originally so fine and it is a dense substance, I also cut the papers up
and soaked those in acetone to recover the traces. Filtration done, I found the solution to be rather dark and I was having difficultly getting the
iodoform back. I decided to remove some of the acetone.
I was aware that iodoform decomposes when heated. I had also noted that the wiki article has expl. written next to it's boiling point. With this in
mind, I began removing the acetone with the mantle at 1 (barely warm enough to boil the acetone), which took a few hours at a drop every ten seconds
or so. I still didn't see much iodoform and the solution was turning into a thicker, darker orange. I realised the iodoform must have already somewhat
decomposed.
I had trouble getting the last 10ml of so of acetone off, so put it under vacuum for the last bits. When I returned, the flask was full of pretty
purple gas and a solid covered in purple. I was fairly sure this was only partial decomposition. Iodine is so dark it only takes a tiny amount of it
to make a mess, and I could still see the leaves of iodoform underneath. But it was still a mess and I decided to reform the iodoform.
Back into the beaker it went! This time I used woelens suggestion alone, rapidly reformed and filtered the iodoform, placed it in a
petri dish and let it dry off a touch for an hour or two on the radiator (45C).
I went straight to recrystallisation with ethanol, which worked out fine. See the pretty end results below.
Things to be careful of
It does decompose quite happily when warmed up, as per my acetone removal experience.
I am also somewhat skeptical of some of the solubility numbers I've seen. I obtained a rough measurement of the mass for mine as 6.4g I think, prior
to recrystallising. To get it into solution, I had to sit the beaker on a hotplate and bring it up close to the boil, stirring away. It took 80-100ml
of ethanol to get it close to all in solution. The iodoform falls back out quickly once the heat is removed. I used some ice to get
as much as possible back out of solution, recovered the crystals, then put the solution in the freezer to obtain a little more.
If you use the bleach method, be aware that iodoform it's self smells kind of like bleach (antiseptic). You may be unable to wash the smell away with
this method because the smell is the iodoform, rather than remaining bleach.
Choosing the bleach method, be sure to use a bleach that is thin and preferably hypochlorite alone, as I suspect it was all the gelling agents that
helped create the superfine, long lived suspension in mine. There is an interesting wiki article in this link describing the use of sol-gels to produce micronic particle sizes, something that previously
required endless ball milling or melting and then spraying a material. Sol-gels are used to create the remarkable substance aerogel.
If you use the bleach method, check the back of the pack to ensure it does actually contain hypochlorite. Wandering around Tescos (a supermarket so
large that 1 in every 8 UK pounds is spent there), I seem to recall their own store brand not directly mentioning hypochlorite on the back.
If you use ethanol in place of acetone, you could likely use meths (denatured alcohol) directly, as the link right up at the top indicates how the
reaction won't be interested in the methanol contaminating your starting material. If you're in the US and have some of that knock out strength
EverClear, that'll work.
Domestos is highly unlikely to work well when attempting to produce chloroform (the chlorine bearing sister of iodoform) via the haloform, as the
amount of gunk in it will probably blend the two phases irreparably into one another.
---------------------------------------------------------
Loads of photos for your enjoyment
my computer sure isn't enjoying the 40 tabs I have open, plus this
This is the iodine I recovered from the methyl iodide. It is sat on a glass cutting board, you just cannee see it through the tissue paper.
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That's KI.
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Booootiful gaaaawld!
It's worth watching this recrystallise, particularly if you pour it out into a cold container, as it will immediately rain back out of the golden
solution as leaves, reflecting sparkly neon rainbows.
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Microscopic scale
I remembered I had this USB microscope hanging around somewhere and thought I'd try it out. It claims 300x magnification. Considering the vast
majority of it is made of plastic, it takes pencil batteries and it cost £9.99, I wasn't holding out much hope. Still... we shall see what it can do!
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91,536,550,800,000,000 molecules of Iodoform
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Hey hey! Not bad!
The microscope is a cronking POS compared to an undergraduate scope; adjusting the stage is nasty, I could fine tune
it by resting a finger on the edge it was that wobbly. But for £9.99 and a little patience, that's not a bad picture. This is at 100x, which is
actually a bit too high I think; it didn't have anything lower. Personally, I'd have preferred it had a 50 rather than the 300x. This is the edge of
the crystal I put on the balance, and the shape reminds me of an SDS masonry drill bit. If I did it again, I'd have grabbed that leaf you can see
floating on the top of the ethanol a few pictures up; scooping it up with the slide. It may not be the nicest miscroscope, but it is still amazing to
me that China can produce this for £9.99. Most people couldn't manage the box for that much; it was £2 for a blank cardboard box from the local
post office.
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Search tags: iodoform haloform iodoform CHI3 methyl triiodide TIM triiodomethane
[Edited on 9-1-2012 by peach]
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[Edited on 7/7/13 by bfesser]
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neptunium
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i made some small amount of iodoform recently as well...
after seperating iodine from a broken NaI detector..
the leftover water/iodine solution was added with NaOH 1N and cooled and stirred
when the color of the solution completly disapear (and wont come back) i added acetone dropwise..
filter and dry
thats it
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AndersHoveland
Hazard to Other Members, due to repeated speculation and posting of untested highly dangerous procedures!
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I do not suppose you would care to react your iodoform with sodium nitrite in DMSO solvent ?
(might want to read of the dangers of nitroform before one tries this... )
http://pubs.acs.org/doi/abs/10.1021/jo01355a612
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jamit
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What to do with Iodoform
Once you make iodoform, what experiment can you perform with it?
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peach
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I have some sodium nitrite and DMSO, but I dislike most things related to anything exploding. You may have to do go it alone on the nitroform.
My aim was to produce all four iodides. Thus far, I've done methyl iodide, this (iodoform) and next I'll reduce the iodoform to diiodomethane with borohydride or phosphorus.
That'll leave carbon tetraiodide.
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neptunium
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how did you synthesised the CH3I ? i`ve tried from methanol H2SO4 and I2 but i dont have any phosphorus ( unfortunatly!)
what is your method IF you start with methanol?
Respectfully
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Hexavalent
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Nice little project Peach, I should note Jamit that the procedure itself can be very useful for the iodoform test.
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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neptunium
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........or should i start a topic ?
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peach
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Neptunium, have a look at this thread for CH3I.
Use phosphoric.
[Edited on 11-1-2012 by peach]
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