havarti_gouda
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questions regarding methylamine synthesis impurities.
i've recently started learning more about amines and decided to try and produce a primary amine. in this case, i am working with methylamine.
i read a few methods and decided to use formalin (37% formaldehyde solution) and ammonium chloride.
500 grams of ammonium chloride was placed in a 1L pyrex erlenmeyer flask and 480mL of formalin was slowly added. the flask was softly heated directly
on a hot plate with stirring to encourage the chunks of nh4cl to dissolve. the flask was swirled a bit and then poured through a funnel into a 2L RBF.
another 480mL of formalin was added to the erlenmeyer with the remaining sludge/chunks of nh4cl. additional soft heating and stirring took place and
then once again, the flask was swirled and poured through a funnel into the 2L.
preparations for simple distillation were made with the 2L placed in an oil bath with full-immersion thermometer lowered into the solution for
temperature monitoring.
the temperature was very slowly increased with a stir bar quite incapable of spinning due to still being covered by a mountain of nh4cl. spinning
became possible between 40-45C and at roughly 75-80C the solution had become completely clear.
the temperature was meticulously monitored and maintained at roughly 90-95C until there was no more distillate and then raised to about 99-100C. this
continued for roughly 2h until there was, again, no more distillate. then the temperature was raised to 104-106C where it remained for about 2.5-3h.
being lazy and not feeling like removing the flask from the distillation setup, receiving flasks were switched and vacuum applied immediately to
remove about 200mL of liquid.
the solution was still very clear with an ever so mild lime green tinge. i continued vacuum distilling and filtering until i had obtained a roughly
60% yield of what appeared to be MeNH2.HCl.
and all was well...
so, the second time i did this...ever so sloppy (for learning purposes).
i decided to scale up slightly. i used about 1kg of nh4.cl and 1.8L of formaldehyde. at the last minute, i realized that my 3L RBF had some crap in it
and figured a 5L would be too large, so i poured out a bit of the formaldehyde from the 2L (from the 1.8L), so it ended up being about (estimation)
850-900 grams of nh4.cl and 1.5L of formaldehyde.
i began distilling and brought up the temperature to about 90C and let it ride. when it appeared to be slowing, i brought up the temperature to about
105C and let that go. i only let the entire distillation go without vacuum for about 4 hours total (assuming the reaction was no complete).
at this point, i had to run out for what i thought would be an hour. i left the stir bar going, turned off the heat on my hot plate and rolled out,
assuming that it would just continue distilling at that temperature and slowly decrease over time as it cooled down. i ended up returning roughly
three hours later. while the solution was a very intense lime green before i left, it was a much deeper lime green when i returned. the last time it
was slightly lime green, but mostly clear and my methylamine crystals had a touch of green, but this time the solution was very very deep lime green.
i applied vacuum and raise the heat up and continued reducing and filtering until i had separated a good bit of the ammonium chloride and methylamine
hcl. i had isolated the bulk of the methylamine and moved it to a 1L erlenmeyer flask and placed it directly on the hotplate to evap. off the
remaining liquid with soft heat and mild stirring.
this is when i fell asleep.
i wake up (5-6 hours later) to find that my previously green/yellow solution is now a deep yellow, almost orange.
i take it off the heat and cool it and the entire mass hardens into what appears to be huge slightly light green/yellow crystals in the flask.
i boiled some ethanol (denatured) and poured it in, swirled it around until everything dissolved (sans nh4cl, obviously) and filtered to remove excess
ammonium chloride. i then allowed the solution to cool and filtered out the "methylamine."
from my reading, my non-reagent grade methylamine crystals will have the mild light green color and dimethylamine crystals could be more yellow-ish.
when dry with vacuum filtration the crystals become significantly more white, but still have a mild less green/more yellow color. i also noticed when
previously evaporating the night before that the smell of formaldehyde was significantly stronger than my previous attempt.
first question: is the presence of excess formaldehyde because the reaction had not completely taken place?
second question: would the dimethylamine crystals be much more yellow? is it safe to say that when the solution turned more yellow/orange, that i had
an excess of dimethylamine/trimethylamine formation?
third question: i've read that the higher methylamines (di, tri, tetra, etc.) have a significantly stronger fish smell than methylamine, however the
crystals from this attempt smelled actually a little bit *less* fishy than my first attempt which was definitely successful, but were certainly
methylamine-esque and not ammonium. is there a possibly other by-product which could've been produced or reacted due to the high temperature over
night? did the reaction contents continue proceeding and produce an excess of di, tri, or tetra methylamine?
thanks for reading my post. i would appreciate any help!
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havarti_gouda
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additional experimentation.
I've done a little bit more research and experimentation and would like to run this by the forum.
I repeated the process again using 0.5kg NH4Cl and 1L of Formalin (37%), and this time, I was once again, very meticulous with technique. However,
this time around, and this could potentially be due to some other factors, I was having a little bit more trouble than usual maintaining the
temperature.
I combined the amine and aldehyde and began thorough stirring with mild heat. When the temperature rose to about 50C, the temperature was nearly
transparent. Around 75-80C, like clockwork, there was slow CO2 evolution which consistently increased. ~93C, the temperature began to plateau and I
had distillate coming over rather quickly. I let the temperature rise to ~98-99C and allowed distillate to come over until it slowed and the
temperature began to drop. This was around 1 hour and 21 minutes into the reaction.
1:21/~99C: Plenty of CO2 evolution, however distillate is beginning to slow.
1:25/~100C: Just tapped vacuum again to remove built up CO2. Ran it for 10 seconds. Distillate coming over at one drop every two seconds.
I raised the tempersture up just a couple of degrees to about 102-103C and I noticed there was really nothing at all coming over. It wasn't until I
raised it to about 104-105C that distillate started coming over again, albeit very slowly. Occasionally throughout the entire reaction, I would turn
on the vacuum, as mentioned in my notes, for about ten to twenty seconds to remove any CO2 which had built up as I am under the impression that the
carbon dioxide can be a deterrent for the formation of mono-methylamine.
2:16/~104C: Distillate is condensing in the condensor much better all of the sudden. Must've been just below the necessary temperature. Appears to be
coming over a bit faster now. Looks right.
2:45/~110C: Let the temperature go a little high. Turned off the heat, letting it cool down a bit. Dimethylamine begins to form over 110, so hopefully
it will be very minimal. The solution is still clear with no green or yellow discoloration, so I can assume that impurities are still pretty low. The
distillate is coming over extremely slow, but if it's supposed to remain within 104-106C, then it would be coming over even slower, so I'm going to
reduce slightly to 106 and maintain it. So far, the receiving flask only has about 300mL of distillate.
I am assuming that most of the methanol in the formalin would have been removed within the first hour or so even with the azetrope formed with water.
Even at 108C, it was coming over at one drop every ten to fifteen seconds.
After 4 hours and 43 minutes, the distillate was coming over at a ridiculously slow pace. I made the assumption that most of the reaction was likely
over at this point and turned on the vacuum. I pulled an additional 30-50mL of what I believe was un-reacted formaldehyde because I got a couple of
whiffs of it coming out of my vacuum pump. This made me wonder if I should've let it go for an extra hour or so, even though the distillate rate was
something ridiculously slow like one drop every two minutes.
At this point, with vacuum, the temperature dropped down to about 89-90C and I started getting distillate again at a fairly quick pace. This continued
for about an hour with the temperature seemingly incapable of climbing above 91C even though the oil bath was around 130C.
After removing an additional 250-300mL of liquid from the mixture, I removed the boiling flask from the distillation setup and allowed it to cool. I
decided to stop at this point for the day, but noticed that the liquid had a *very* mild greenish hue that was beginning to come on, but it was
extremely light and the clear solution looked like water other than the mild greenish hue.
Learning about the dimethylamine production being much more focal with the temperature above 110C really put into perspective the reason that when
evaporation one should use a steam bath. And this is likely why the solution in my second attempt went from a lime green to a yellow/orange when I was
evaporating direct on my hot plate. Being that there was additional formaldehyde in the solution along with ammonium chloride, obviously, it began
reacting and producing dimethylamine.
I've thought about using the method where one hydrolyses hexamine instead of this method, however, didn't have any 28% ammonia hydroxide solution on
hand and didn't feel brave enough to pull the ammonia gas from a NH4Cl solution with NaOH.
However, what I am a bit confused about is that I've read on another post from this forum regarding methylamine synthesis that formaldehyde and
ammonium chloride reduce to methylamine and that hexamine reduces to formaldehyde and ammonium chloride. Some people suggested, why start with
hexamine instead of formaldehyde and ammonium chloride if it will only break down into those two products anyhow? However, when using the method I've
been using, obviously it is necessary to distill at 100C and then bring it up to 104C to get certain products out of the solution. Is this same
function necessary when hydrolysing hexamine? From the hexamine hydrolysis method I was reading, it seemed like it was quite simply a means of adding
HCl to the hexamine, raising the temperature and distilling off volatile solvents and then evaporating off the liquid to yield Methylamine HCl. It
seems very similar to this wherein by bringing it up to 100C and then 104C, I am removing additional solvents and by-productions of the aldehyde
breaking down. If I was to simply evap off the liquid after removing solvents/by-products at 100C and 104C, it would yield NH4Cl and then MeNH2Cl as I
separated the fractions. The fractional separation is rather time consuming and, even moreso, laborious, and it seems like evaporating off the water
from a hexamine/hcl mixure would be significantly easier, albeit taking longer. Are these methods just about identical, with exception of the precise
steps?
Thanks! Any help would be greatly appreciated!
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bbartlog
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I don't know exactly what your distillation setup looks like - specifically, whether you have any sort of column before the head, or whether you're
just doing simple distillation. However, I think it would be helpful and informative to you if you were able to monitor the temperature of the vapor
passing through the head. I have recently rearranged things so that I have one thermometer in the solution and one in the still head, and it gives a
much better picture of what's going on, as the difference in temperature can be quite significant and the head temperature is much more useful for
trying to figure out what is passing over at any given moment.
As for the rest of your questions, I don't know. It sounds like your procedure is loosely based on the one from Organic Syntheses, so you are likely
familiar with the purification methods described there - in fact I see you recrystallized from ethanol. But you omitted the wash with cold chloroform
which is specifically intended to remove dimethylamine HCl, and if you look at their weights (pre- and post- wash) this does not seem to be some
trivial constituent. Also, you describe your ethanol as 'denatured' which makes me suspect that you are using some OTC drugstore ethanol. I am a big
fan of OTC reagents myself (when practical) but unfortunately denatured alcohol such as can be obtained off the shelf tends to be really unsuitable,
it seems to have quite some junk in it.
I would suggest getting some chloroform and (real) ethanol, and then attempting the synthesis on a smaller scale at first. Chloroform can be readily
made from acetone and sodium hypochlorite bleach, if you can't source it online. Absolute ethanol is likewise something you can make yourself, either
by distillation/drying of various spirits or starting from sugar and yeast.
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havarti_gouda
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I am set up for simple distillation with boiling flask in oil bath over hot plate/magnetic stirrer, connected directly to 3-way adapter, with
thermometer adapter attached on top joint (and thermometer lowered into solution) and side joint connecting to a liebig condenser followed by a vacuum
adapter running into receiving flask. using a thompson diaphragm vacuum pump which pulls up to 29in (whatever that translates to in torr or mmHg, i
wish i knew).
Yes, I am familiar, but I just didn't have any chloroform on hand, otherwise I would've used that to remove the dimethylamine, or to at least test the
crystals from second run. I didn't realize chloroform was so easy to make.. I will search for the synthesis you're referring to.
The (fake) ethanol is definitely wild card-style. I can smell some methanol in it, so I'm assuming it's predominately ethanol, a little methanol for
poison, more than likely a bit of water, and possibly even a cocktail of other random things. So, I was assuming there would certainly be at very
least a bit of ammonium chloride and dimethylamine impurity, I was just hoping that I could minimize dimethylamine production by keeping the
temperature reduced for the entirety of the reaction!
Regarding the EtOH, when you say distillation/drying, would it be better to simply dry some 95% everclear with something like mgso4 or distill
everclear with a vigreaux column packed w/ a drying agent? Can EtOH/water be "salted out" like isopropyl alcohol?
Thanks for your help!
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bbartlog
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Chloroform can be made from acetone and hypochlorite by the haloform reaction. It proceeds easily and the yield is very good (percentagewise), the
only problem is that because the reaction is exothermic and chloroform is easily vaporized you need either cooling or else a contained setup where you
can distill the chloroform directly from the solution of reagents. Also, in terms of volume of chloroform per volume of bleach you may find it
underwhelming: one standard US bottle (1.42 gallons) of Chlorox has about 4.2 moles of sodium hypochlorite. Since three moles of hypochlorite are
consumed per mole of chloroform produced, you would get maximum 1.4 moles of CCl3 per bottle of bleach, and 1.1 moles is more realistic unless you
really do some work to get all the product out of solution. That's 130g of chloroform per bottle of bleach, less than 100ml. Still, bleach is pretty
cheap if you're willing to do the work. And if you have a five liter RBF and can set it up right you may be able to do batches of decent size, half a
bottle at a time or so.
As for drying ethanol, I suggest searching for some existing thread. Pretty sure it's been discussed to death. But keep in mind that you don't need
extreme anhydrous ethanol like someone might want for certain organic reactions; you're just trying to make sure that not too much other stuff
dissolves with your methylamine, so the difference between 99% and 99.99% dry probably wouldn't be worth the effort for you.
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havarti_gouda
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I've read about that chloroform production reaction. I think I was reading on some site (which I believe was intended for illicit purposes, so there
seemed to be an extreme lack of safety/cleanliness) about using like a 50 gallon drum and filling it with acetone and bleach and dumping ice into it
or something. Seemed like some sort of major hazard waiting to happen. :-)
I imagine there's a thread about this, but I'll ask anyway. Is there anyway to isolate the sodium hypochlorite from the bleach or at least reduce the
liquid significantly enough to be able to run the reaction at a 16.8M or 21M level? I'd like to generate at least half a liter. From a learning
perspective, I'd really enjoy to perform the reaction and would likely do it at a small scale, but I imagine I would need chloroform for other
purposes down the road and would like to generate at least 5M worth. I wonder how cost effective it would be. Is chloroform a "watched" item? I guess
a common view is that just about everything is "watched." Hah.
Regarding the ethanol, I've been running into a small issue when re-crystallizing, where there would be a small remaining amount of H2O in the
crystals, or the ethanol is pulling water out of the air or something, so instead of heating the ethanol and the NH4.Cl settling at the bottom, the
entire solution clears and then NH4.Cl starts precipitating out along with the MeNH2.Cl. I imagine I will have to evaporate off a bit more liquid and
then re-crystallize again. It's just been really annoying.
I'm really excited to produce some chloroform however, as I have MeNH2.Cl from several runs in varying colors! Some is light green, some is *almost*
pure white (but definitely has the crystal structure of MeNH2.Cl, not NH4.Cl), and some has a mildly yellow hue. I'm really curious to identify what
is monomethylamine vs. di/trimethylamine.
Many thanks for all your assistance! Cheers!
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bbartlog
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I've seen a post describing the ice-in-a-bucket (plus bleach and acetone) method. It does deal with the heat produced by the reaction, and temper the
rate, but I don't like it because chloroform is very slightly soluble in water and so you end up with even lower effective yield as a result of having
added (even more) water. When I did it I added 700ml at a time of the hypochlorite bleach to a 1L Erlenmeyer flask, then carefully added a bit of
acetone (7-8 ml at a time) that sat on top of the bleach, turning yellow and getting hot. I held it under running cold water, holding a stopper in
with my thumb, and occasionally shook it gently, pausing to cool it as needed. Then added a little more acetone, and repeated until the reaction
ceased. Doing it this way is some combination of finicky, accident-prone and labor-intensive, however; so I don't actually recommend it. If you have a
RBF with more than one neck I'd suggest filling it half full with bleach, setting up a condenser and receiver, and then adding the acetone; the heat
of the reaction will help drive the chloroform into the receiver, and while it's an exothermic reaction it's within reason when using a 6% solution of
bleach.
You could concentrate the bleach beforehand, but... the extra thermal mass of the water helps keep the reaction at least partly under control, and
distilling out the chloroform afterward is easy enough, so I don't see much point (also bleach I think can decompose or disproportionate at high
temperatures). Some people use bleach powder (Ca(OCl)2), which is much more concentrated, but then you have to assume you're going to vaporize all the
chloroform as it's produced and plan accordingly.
As for 'running the reaction at a 16.8M or 21M level', I recommend doing the math on the molarity of a saturated bleach solution: as far as I can tell
a saturated solution at 0C is about 4M and at 25C more like 6M, and even some hypothetical 100% melted bleach would not have the molarity you mention.
Anyway, you can generate half a liter if you really want to; it's dense, so that's 750gm, so I'd estimate you'd need to get 7 bottles of bleach or so,
which would set you back no more than $30. Plus about a half liter of acetone. I suppose if I were looking at such volumes I'd be wondering about the
feasibility of 50 gallon drums as well; maybe you'd be better off ordering it. I don't think it's 'watched' by the DEA as it's not much of a precursor
to anything as far as I know, but given its medical history as an anaesthetic it's entirely possible that some other set of restrictions applies.
Anyway, if you just need something to wash out the dimethylamine, there may well be other solvents that would work. It is likely that the workup in
Organic Syntheses was done using chloroform because it was handy at the time. You could do a trial with some other relatively non-polar solvent (DCM,
hexane, ether, or whatever you find convenient), on some *small* portion of your product, and see what happens. Or you could do some research on the
solubilities and see if anything else looks suitable.
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havarti_gouda
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I actually don't have any multi-neck RBFs any more. Ahh, tricky hands dropping things. :-(
How fast does the reaction proceed? Would it be possible to say, set up for simple distillation and fill a 2L RBF with 1.3L bleach (slightly less than
double what you suggested just to give the reaction a little bit more space) and throw in a stir bar. Take off the thermometer adapter and throw in
like 10-12 mL of acetone. Would I have enough time to re-attach the thermometer adapter before the chloroform flew out of the top, or would it be
possible to add a bit more even and then re-attach therm adapter, and turn on the stirring to really get it going and condense the chloroform like you
suggested? Then just perhaps add a little bit more acetone once it appeared no more chloroform was coming over and continue adding until the ratios
for the reaction had been met and then remove used bleach solution and refill. I imagine I could even bring up the heat a wee bit to distill over any
remaining chloroform once the reaction cooled or just put it on an ice or ice/salt bath and use low vacuum? I really like the idea of having the
condenser set up, seems like it would really save a lot of time. If that worked pretty well, I might try to scale up to using a 5L as that's the
largest rbf I have. In fact, while reading over what I typed, I just thought that, especially at larger scale, the reaction could potentially get
really hot. I imagine that even when condensing a bit at a time, I'd have to keep it on an ice/salt bath just to regulate how much was coming over so
it doesn't fly out through the vacuum tube. Maybe just very slow stirring here and there? Thoughts?
I was considering trying dcm or maybe even o-xylene. I'd just be worried about not knowing what is where if there was a solubility change since the
Merck is limited in sol. data for MeNH2 and 2(MeNH2).
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bbartlog
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What you suggest would work. If the acetone is added gently and the bleach starts cool, the acetone will form a layer on top that turns yellow (and
gets hot), but the scope of the reaction will initially be limited by the separation of layers. Not until you agitate/stir the mixture would it fully
react, and even then it does take a couple of minutes. You could probably add the entire stoichiometric amount of acetone at the beginning, so as to
avoid having to reopen the flask multiple times during condensation.
I believe that slow stirring would do the trick as far as maintaining the temperature at a reasonable level. While the reaction is exothermic and thus
self-accelerating, it tops out at simply boiling off chloroform; you don't have to worry about explosion or fire as long as you're working with 6%
bleach. Also, while chloroform is low-boiling and does have some vapor pressure at room temperature, it's not really that hazardous(*); you can smell
it easily, you'd have to breathe in quite a bit to knock yourself out, and it doesn't cause burns or cumulative damage. Not nearly as scary as
chlorine or even HCl fumes in my opinion. So you don't have to go through contortions to try to instantly close the flask after adding the acetone.
You probably will need additional heat to drive over all the chloroform. It will form a layer at the bottom of the flask, being nearly one and a half
times as dense as water. So you can tell when most of it is gone. Theoretically, it should then also be possible to distill over the small amount of
chloroform dissolved in the aqueous phase, but I have not had much luck with that.
If you are inclined to try to find uses for your leftovers, it's also worth pointing out that (after the reaction and distillation) the solution in
the flask has quite a bit of sodium acetate in it, which can be crystallized out if you have the time for it. But the liquid volume is big enough that
it's probably easier to just dump it.
(*) to quote the EPA: 'The major effect from acute inhalation exposure to chloroform in humans is central nervous system depression. At very high
levels (40,000 ppm), chloroform exposure may result in death, with concentrations in the range of 1,500 to 30,000 ppm producing anesthesia, and lower
concentrations (<1,500 ppm) resulting in dizziness, headache, tiredness, and other effects.'.
Those are very high levels. Compare chlorine: 'mild mucous membrane irritation at 1 to 3 ppm; chest pain, vomiting, dypsnea, and cough at 30 ppm; and
toxic pneumonitis and pulmonary edema at 46 to 60 ppm'... it's a hundred times more poisonous.
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havarti_gouda
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Okay, that's ideal. You mentioned the leftovers, and in fact, I'm in need of acetic acid as well. This works out just about perfectly too, because
rather than performing a separate reaction to generate acetic acid and purify, I imagine I would be able to simply isolate out the acetic acid through
distillation after collecting all of the chloroform distillate.
I love when a reaction has a byproduct that I need as well and can do a little extra work to avoid having to do a separate reaction all together. Ahh,
the benefits of science!
Just to clarify, you mentioned that I will need 3M sodium hypochlorite to generate 1M CCl3, but didn't mention the molar ratio for the acetone (or
maybe i just missed it.) If I would need about half a liter of acetone to generate a liter of chloroform, I'm guessing it'll be ~0.5M (about 28g)
Acetone per 3M Sodium Hypochlorite to generate 1M Chloroform, correct?
What quantity of the left overs would be acetic acid? I'm not very good at balancing equations yet.
So, I'll pre-add the bleach, set up for simple distillation and attach the boiling flask to the system. Then remove the thermometer adapter and add
the acetone from an addition funnel, (or better yet, i'll put it in a non-jointed sep funnel and let the stream of acetone hit the side of the flask
so most of the downward velocity is reduced by running down the side of the flask instead of going directly into the solution, so it collects better
on the top.) And then re-attach the therm adapter and use mild stirring with occasional pauses once the reaction is moving along to assist with
maintaining the temperature, then I can avoid having to switch out baths from ice to oil. Then let the reaction assist with distilling over the
chloroform as it's being generated until the temp drops <40C and then apply a gentle heat to bring the rest of it over. Once I've collected as much
of chloroform distillate as possible, I'd like to simply switch flasks and bring over the acetic acid at ~118C, but there's going to be a significant
quantity of water to make that rather time consuming. This is why I'd like to reduce the bleach a bit, but just like you were saying, it will likely
get too hot. I guess I'm either going to have to be switching out baths or be stuck distilling over a lot of water before the acetic acid comes over.
Any suggestions?
I don't need GAA or anything, just some like 80% AA for my alcohol to carbonyl compound reaction. I imagine it would be a particularly un-concentrated
volume of acetic acid, but since I'll be going through 20-25M of sodium hypochlorite, I should be able to distill out enough to conc. the solution to
roughly 80%, but likely lacking volume. In fact, if it is a straight byproduct from the chloroform production, should I get a near molar equivalent to
the amount of acetone I put into each run, or am I totally off with that assumption?
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starman
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He said sodium acetate not acetic acid.The salt will need to be isolated first and AA distilled from (usually) sulfuric acid.
Chemistry- The journey from the end of physics to the beginning of life.(starman)
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entropy51
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| Quote: | | If the acetone is added gently and the bleach starts cool, the acetone will form a layer on top that turns yellow (and gets hot), but the scope of the
reaction will initially be limited by the separation of layers. |
Now why would acetone form a layer on top
of bleach, which is mostly water?
It might be better to consult an actual chemistry book for CHCl3 prep. The discussion above is pretty far-fetched. (Should be in Whimsy?) The
volumes are more manageable using Ca hypochlorite instead of gallons of bleach, but there are significant opportunities for a runaway.
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bbartlog
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So far as the stoichiometry goes, I believe the net reaction is
3NaOCl + C3H6O -> NaC2H3O2 + CHCl3 + 2NaOH
So you need one mole of acetone per three of hypochlorite.
As starman already noted, you will have sodium acetate, not acetic acid, in solution. Also, while the reaction is relatively clean, there are still
some side reactions along with impurities in the original bleach. So acidifying and concentrating would mostly make a mess. Boiling down and cooling
to crystallize out the sodium acetate, then treating with sulfuric acid and distilling, seems more sensible - but still a lot of work for the amount
of acetic acid you'd end up with.
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bbartlog
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| Quote: | | Now why would acetone form a layer on top of bleach, which is mostly water? |
Try it and see. In this particular case I don't need to consult a chemistry book, as I have done the prep seven times. Whether the yellowish layer
forms because of the existence of some intermediate in the reaction, I can't say. If you look closely at it and don't disturb it by stirring, you end
up seeing tiny globules of chloroform dropping down from the boundary, through the aqueous phase. Once it's agitated it becomes too turbid to see
this, though.
[Edited on 27-1-2010 by bbartlog]
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havarti_gouda
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Ahh, my mistake. I guess I just assumed there would be AA there due to the NaOAc. Perhaps I'll just go ahead and order the acetic acid. :-) I'll post
results on chloroform reaction in a couple days.
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havarti_gouda
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So yesterday I tried using DCM, but just like I was afraid of, I'm not completely sure of what is what exactly, but from a visual perspective alone,
it looks like sweetness. :-)
So, I added just a small bit of some of the prettier MeNH2Cl crystals that I've had sitting in a make-shift desiccator for the last couple of days to
a small pyrex flask and added a few mL of DCM. I swirled it all around and it seemed like it didn't do too much, so I threw it on some mild heat and
brought it up to maybe 35C with occasional swirling over top the hot plate. Once again, not too much. So, feeling pretty comfortable that I wouldn't
be ruining my MeNH2Cl, I added a significant amount (maybe 0.5kg, which is all of it from my last couple of experiments). I added just enough DCM to
cover it and began swirling. The solution became very cloudy! When I vacuum filtered it through my Buchner funnel, the crystals were waaaaay more
shiny, slightly less green (but still had a mild, light green hue), and either the yellow crystals were gone or the yellow removed from them (there
were some nearly white ones from when I had maintained the temperature pretty low the entire time). All of the crystals looked beautiful! Super
shimmery and brilliant. I saved the DCM with whatever it is in it, but I don't know if it's dimethylamine, but something certainly is in the DCM as
it's pretty green/yellow.
When I said 0.5kg earlier, I was estimating, as I didn't weight it before washing with DCM, but the weight clocked in at 434.56 gms after and it
physically looks like less than before. This could also be possibly due to my DCM not being anhydrous, but I wouldn't expect the crystals to get
significantly better looking if the DCM did nothing and my weight reduction is exclusively from water dissolving some product.
[Edited on 29-1-2010 by havarti_gouda]
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