Problem with Chloroform via Haloform reaction

Quote: Originally posted by Octavian

The first drops hit the receiving flask at a head temp of 49C with 2 drops per second, and was kept at 1-2 drops per second all through the distillation. The first 50-60ml come over at a constant head temp of 49C to 49.5C, some time after that the flow slowed a little and the head temp dropped as low as 44C but raised back up only to drop again, this continued to rise and fall from 44C to 51C until I had collected exactly 100ml at which point I ended the distillation. The boiling flask still contained approximately 30-40ml and most of the CaCl2 had dissolved.

My thought would be that there are multiple hydrates of CaCl₂, someone correct me if I am wrong but usually a distillation is not done over CaCl₂. I have seen distillations over Na, LiH, CaH₂, etc, but not CaCl₂. The most hydrated forms of CaCl₂ give up their water of hydration easily on heating. My thought would be since there was only liquid left in the pot when the distillation was complete that the CaCl₂ had dissolved in its own water of hydration. In which case it was likely saturated with water in the first place, again with the mention of initial haziness the first thing I thought was that it was not dried completely.

Did you use powder or prilled CaCl₂? It's hard to tell a complete drying with prilled anything, with powder you watch to see if it clumps up. You keep adding till it is free-flowing (never tried this with CaCl₂ which sometimes takes much more than expected. What type of CaCl₂ did you use, OTC? Do you have any idea how dry it was?

Aga, I did not mean to insinuate that CaCl₂ doesn't absorb any water. Just that it is not the best desiccant in the chemist's tool box since it can give up the water easily and does not bind it that strongly. Especially if it is left in the flask during the distillation. But all of this is just conjecture based on Octavian's opening post. Chucking powdered CaCl₂ into a flask with chloroform with water contamination until it is free-flowing and then filtering to remove your drying agent does seem like a reasonable way to dry the chloroform, but as usual the devil is in the details and there are a number of ways it could go wrong based on your technique or reagents no matter how simple it sounds on paper.

Edit: As much as I dislike using Wiki as a source, this is relevant

Thank you for all the help. To answer some of the questions:

I was using a water bath on a hot plate for heating with no stirring and nothing to measure pot temperature. I didn't consider that my thermometer would be that far (4C) out but now I'm actually keen to try testing it. I skimmed thought Vogels last night and found that he recommends drying chloroform over CaCl2 for at least 24 hours prior to distillation. I was surprised at how milky white my chloroform was right from when it was decanted from the original bottles, from examples I have seen on youtube it seems it's usually quite clear from the start, I am still strongly suspecting that the one bottle that also contained some kind of detergent is the source of at least some of my problems.

I can't remember where I read to distill the CHCl3 over CaCl2, so sorry that I can't reference that. The CaCl2 I used was just standard OTC "DampRid" and not powdered. Also I had no idea that CaCl2 would give up it's water so easily when heated! I'm thinking of taking the 100ml that I recovered and trying to dry it for at least 24 hours over CaCl2 and seeing what effect it has on it's appearance, unless I'm mistaken the CaCl2 will also take out the 1-2% EtOH I added also, yes?

Again, thanks for all the help. Even if I end up failing this synth I've definitely not failed to learn something!

Hi, Octavian!

I've been using 27.5ml of acetone for 2l of 5% bleach (I believe this is around 1.424 moles of NaClO, so you use three times less acetone). I've always got only around 50% or little higher yield, which in this case (theoretically) should be 38ml of CHCl3 (someone please, correct me if I'm wrong) so, usually I get about 20ml or little more, though I don't know what is practical yield percentage limit for this reaction (it'd be helpful if someone knows). I know that some of it is lost due to exothermic reaction, but not much if it's well cooled. My chloroform is sometimes cloudy too, but not always (I think it has something to do with too much of acetone being used, although I'm not sure). And also as others have said, don't leave it in reaction mixture so long (I usually let it sit for only one or two hours or so, but last time I did it I think it was only 1/2h - maybe it might be even better to leave it in there for even shorter amount of time). I'd definitely recommend you to stir it really well while adding acetone (so that reaction is more efficient), also add acetone really slowly (don't let the mixture heat up above 30°C/86F/303.15K). If you do all of that, the chloroform should sink to the bottom really quickly, so you can remove it before the reaction proceeds and destroys your chloroform.

Hope this helps

BR, xfusion

Quote: Originally posted by xfusion44

My chloroform is sometimes cloudy too, but not always (I think it has something to do with too much of acetone being used, although I'm not sure)

I thought I would update this thread with my latest progress .

I checked on the 100ml bottle of CHCl3 that I had previously collected a couple of days ago and to my horror it was only half full, even with PTFE thread tape over the mouth of the bottle and the threads the shitty cap must have still allowed it to slowly evaporate, thankfully I tend to plan for the worst and this is exactly why it was stored outside of the house where the only drama was losing half of it. So I dumped what was left into another batch which was made the same way (but with correct stoichiometry this time allowing for a slight excess of NaOCl), however three of the four bottles (IIRC) contained a detergent and left it a hideous milky white colour that would eventually form a layer on top of the CHCl3 if left for a good week or more but would instantly cloud up at the slightest movement. This second batch had been sitting under water w/ some EtOH for a good 3-4 weeks waiting for me to get around to cleaning it, anyway...

Most of the water from the second batch was decanted off along with some of the detergent, it was then poured into a sep funnel and the remaining 50ml or so from the original run was poured in with it, a roughly equal volume of water was added and the funnel shook well for about 45 seconds and then was left an hour to settle (I was doing other things and it took an hour to come back to it), The slightly clearer but still milky bottom layer was drained into a 250ml RB flask containing about 1tsp of CaCl2 and was stoppered. This was swirled around every 10-15 minutes over the next 2-3 hours and then left for another 3 hours, worth noting is that it cleared a little in the first half hour but then returned to it's original colour shortly after.

The chloroform was decanted off of the CaCl2 and filtered using a coffee filter and gravity filtration, in no time the detergent gummed up the filter paper and it took forever to get it filtered. The filtrate was still quite cloudy but not as much as before. The next day the CHCl3 was poured into a 150ml RB flask setup for standard distillation using a water bath and a few boiling chips, this time I used a different thermometer - a mercury one which seems much more accurate, the first drops come over around 50C and around 5ml or so was collected before the head temp settled on 60C and the receiver was swapped, almost everything else come over at 60C - 61C until there was around 10ml of foamy crap left in the boiling flask and the head temperature began to drop back into the 50's. This left me with exactly 70ml of crystal clear highly refractive chloroform, I then added 1ml of 95% denatured EtOH to stabilize it and to my horror it turned cloudy - I'm assuming that would be due to the few percent H2O in the EtOH . Aside from aesthetics I'm thinking I can chalk this up as somewhat of a success.

tl:dr: Beware of bleach containing detergents, they're not listed on the label but you can easily tell by shaking the bottle and opening the cap, if it has foamy bubbles, find another brand because it's a pain in the butt to clean.