Sciencemadness Discussion Board

I think I used too much acetone for this Chloroform prep

Buchnerfun - 14-2-2015 at 13:19

Greetings fellow hobby chemists. I know its bad form to join a forum and ask a question on your first post, but I just finished a preparation of Chloroform and something has clearly gone wrong.

I use Chloroform for several things, mostly I use it to euthanize insects for my entomology boards. I know it can be purchased online but whats the fun in that?

Anyway I prepared it using the Haloform reaction of Acetone and Sodium Hypochlorite. They were mixed in an ice-bath and left overnight. This morning I used a sep funnel to isolate the chloroform.

Instead of the nice, refractive, translucent substance I was hoping for, I got something that looks more like milk. I decanted it into a Florence flask ,wrapped it in aluminum foil, added a few drops of ethanol to prevent phosgene formation, and stuck it in the freezer.

I'm a o-chem student at my local university, although I haven't actually gotten to o-chem yet, still doing my gen-chem stuff.

Anyway, I was thinking of getting myself a distillation apparatus for my birthday, but I was wondering what you guys think


Did I use too much acetone? when wafted the solution smells sweet like chloroform but also harsh like acetone.

Will this be relatively simple to distill out?

Are there any other methods of removing these unwanted substances in the mean time?



Additional info:

it was obvious all of the NaClO had reacted, as the hallmark yellow color had been completely reduced to cloudy water.

My reagents were store-brand laundry bleach and 100% unadulterated acetone

90mls of acetone were slowly added to 2liters of what I was told was 10% NaClO solution, resulting in about 31mls of unrefined chloroform milk

Should I try titrating NaClO into the mother-liquor to get rid of the unreacted acetone?


Sorry for the long post, I'm always a bit giddy after a home experience, even when something goes wrong.


Cheers, thanks for any replies

tl;dr

Attempted to synth trichloromethane, ended up with milky substance denser than water, can anyone point out my mistake or let me know another method of seperating these two compounds?





gdflp - 14-2-2015 at 13:30

Laundry bleach is typically 5-8.25% NaClO, I've never seen any 10% bleach but it's still quite possible. I didn't run the calculations, but it seems to be an excess of acetone, when making chloroform it is typically preferable to use an excess of hypochlorite, as acetone and chloroform form an azeotrope. I don't believe that acetone would cause the chloroform to be cloudy though, I would assume that this is either due to a contaminant in the bleach or the chloroform has suspended water. Trying letting the chloroform sit over anhydrous calcium chloride, magnesium sulfate, sodium sulfate etc. to remove the water from the chloroform.

Buchnerfun - 14-2-2015 at 13:45

Thanks gdflp, that's a great idea. Fortunately I have some magnesium sulfate on hand, added about 2 or 3 grams to the mother-liquor, I'll report back later to see if that helped.

Bot0nist - 14-2-2015 at 15:06

In my limited experience, unless a large excess of cold and alkaline sodium hypochlorite solution (bleach) to acetone is used, then the formed, crude trichloromethane will be contaminated by a significant amount of unreacted acetone, which can form an insoluble layer as well, if the remaining bleach ( aq. hypochlorite/NaOH/NaCl solution) is concentrated enough.

Using a large excess of chilled hypochlorite solution, with strong cooling and stirring throughout the reaction will help insure that your limiting reagent (acetone) has fully reacted. Follow this up by doing a distillation of your crude chloroform with a good column to help separate what remaining, unreacted acetone you can. Then use boiling point determination, known solubility data and other physical property tests on the resultant purified chloroform to help establish it's purity, with a decent degree of accuracy.

Edit: ps.
An incomplete reaction, dissolved acetone, water, or other inpurities can all cause a turbid, cloudy look. Ensuring a complete reaction, drying, and fractional distillation of the crude trichloromethane should help resolve this.



[Edited on 14-2-2015 by Bot0nist]

[Edited on 14-2-2015 by Bot0nist]

Buchnerfun - 14-2-2015 at 16:56

Quote: Originally posted by gdflp  
Trying letting the chloroform sit over anhydrous calcium chloride, magnesium sulfate, sodium sulfate etc. to remove the water from the chloroform.


This worked like a charm. Unfortunately my magnesium sulfate was already hydrated, but that just meant I got to break out the crucible and dehydrate it.

I put a little bit of extra powdered anhydrous MgSO4 in my sep funnel and poured in the solution.Came back a while later and drained the solution through the MgSO4.

My new yield is 13mls of clear solution, so your advice was amazing, won't be forgetting that lesson any time soon.





[Edited on 15-2-2015 by Buchnerfun]

[Edited on 15-2-2015 by Buchnerfun]

[Edited on 15-2-2015 by Buchnerfun]

[Edited on 15-2-2015 by Buchnerfun]

Buchnerfun - 14-2-2015 at 17:14

Quote: Originally posted by Bot0nist  


Then use boiling point determination, known solubility data and other physical property tests on the resultant purified chloroform to help establish it's purity, with a decent degree of accuracy.

Edit: ps.
An incomplete reaction, dissolved acetone, water, or other inpurities can all cause a turbid, cloudy look. Ensuring a complete reaction, drying, and fractional distillation of the crude trichloromethane should help resolve this.




Thanks, I won't have a proper distillation apparatus until Wednesday.

As for the simple purity and property tests, could you walk me through how you would do them? I have a very rudimentary setup at this point.

I thought about titrating NaClO slowly into the crude trichloromethane to see if a reaction occurs and then I could simply stop titrating when no more reactions occur, sep off the chloroform, and distill it when my new toys arrive.

Buchnerfun - 14-2-2015 at 17:16

Does anyone know an economical way (aside from distillation) to remove acetone from Chloroform?


Thanks for your help everyone, I think experiment #2 is going to go much, much more smoothly.

[Edited on 15-2-2015 by Buchnerfun]

[Edited on 15-2-2015 by Buchnerfun]

Bot0nist - 14-2-2015 at 20:27

Finding it's boiling point should be pretty straight forward, as long as you have a suitable way to accurately take temperature.

I would probably use an oil bath for heat with a thermometer in it, and a small RBF less than half full of the crude chloroform and a small stir bar, partially submerged in the oil bath, and a thermometer in it as well clamped in place. Heat and monitor the oil baths temp, as well as the crude isolates temp. Use very gentle mag stirring in the RBF and careful observation. Record the temp in the rbf, as well as the oil temp the moment you see the crude chloroform start to boil. Compare the observed bp of your crude product with that of pure trichloromethane's. Impurities ( like acetone) often lower the bp.

As far as other physical properties, just check pure chloroform's data and see what distinguishing properties you can easily test and compare.


Edit: IIRC, The last few percents of acetone (up to 20%??) Is hard to remove, even with a decent column. Best to try and avoid excess acetone in the initial reaction, and ensure optimal conditions to avoid the contamination issues during the final workup.

[Edited on 15-2-2015 by Bot0nist]

Buchnerfun - 15-2-2015 at 11:29

Quote: Originally posted by Bot0nist  



Edit: IIRC, The last few percents of acetone (up to 20%??) Is hard to remove, even with a decent column. Best to try and avoid excess acetone in the initial reaction, and ensure optimal conditions to avoid the contamination issues during the final workup.

[Edited on 15-2-2015 by Bot0nist]



Thanks for the tips, next time I'll definitely test the purity of the NaClO and not just assume.

I know there's a device where you essentially connect a graduated cylinder upside-down connected to a two-necked round bottom flask and measure the change in volume based on the gas which bubbles from the NaClO, no idea what its called though

Fantasma4500 - 16-2-2015 at 09:00

well the best method, buchner.. would be to simply add more NaClO
but at least your chloroform doesnt magically disappear like mine does, dumping your acetone/chloroform in concentrated NaCl solution and running electrolysis on it with titanium and MMO should be doable aswell, and also for producing the chloroform, supposing the acetone/chloroform ratio would at one point favor chloroform so much that there wouldnt be any acetone left

The Volatile Chemist - 16-2-2015 at 15:32

Excess acetone produces 'chlorobutanol', which would contaminate the product, I'm fairly certain, if there was much acetone in excess.

Zymurg - 25-2-2015 at 01:22

Hi everyone,
just joined up, saw this post and thought I'd offer a few pieces from my experience, having played with the haloform reaction a bit. have made plenty of chloroform and some Iodoform with it.
*PLEASE EXCUSE MY LACK OF DEFINITIVE FIGURES, THE HARD-DRIVE CONTAINING MY NOTES FLAT-LINED AND WAS PRONOUNCED DEAD ON ARRIVAL, SO I AM RELYING ON MY MEMORY*

Haloform Reaction- Synthesis of Chloroform
i) the reaction occurs best in basic conditions (without basing the HClO solution, the reaction yielded a greeny yellow solution that was miscible in the reaction mix- possibly some sort of chloracetone or the chlor-butanol mentioned above)
ii) never used household bleach, used pool chlorine (variable % HClO content- tops around 30%)
iii) reaction gets hot and gets away from the unwary chemist quickly, so appropriate cooling is a must. Even if reaction is effected slowly, with spacing between addition of acetone aliquots the reaction mix will get hot enough to boil off the product as it is forming.
iv) the reaction mix proceeds through several color? changes, The milky phase is the 2nd, a clear, colorless reaction mix displaying 2 distinct phases (the bottom phase is the product) signifies the endpoint.
v) the reaction doesn't seem (in my opinion stemming from my experience with it) to need to be exactly quantitative. What is required is an excess (roughly 15x with pool chlorine, about 35x with household bleach) of the basified hypochlorite solution to the acetone. If done carefully with appropriate cooling a quantitative yield of chloroform: acetone is yielded.

Here's how I have effected the reaction (roughly, I am going back aways into the depths of my memory here)

a) mixed 500 mls of water with 20 g NaOH
b) added the above to 1.5 L of straight pool chlorine (NaHClO circa 30%) as purchased , in bulk from the pool shop.
c) placed the resulting yellowy solution in the freezer till it chilled down. In fact the entire synthesis is carried out without removing reaction mix from the freezer. When mix is chilled down to roughly 0 degrees addition of acetone may commence
d) Measure out 100 mls of store bought acetone. Under no circumstance should the entire volume of acetone be added to the reaction vessel. Initially acetone may be added in somewhat larger aliquots (15 mls) but as the reaction proceeds the aliquots should be decreased (10 mls down to 5 mls to 1 or 2mls nearing the endpoint) judged from the appearance of the reaction mix. Also the additions need to be spaced adequately so as to allow the heat of reaction to dissipate, the intervals being lengthened as the reaction proceeds. It will be noted on commencing addition of acetone, that a yellowy, milky region forms where the acetone contacts the reaction mix. Shake or stir reaction mix after each addition. After the entire volume of acetone has been added as portions, leave batch in the freezer to ensure completion and allow all of the product to separate out and fall to the bottom of the reaction vessel.
e) the reaction undergoes several changes in colour and opacity, following this order
yellow, milky patches -> yellow, milky reaction mix -> the yellow fades to white, remaining milky (this is the point where the reaction will get out of hand if its going to, be very aware of the temp of the reaction vessel) -> the opacity starts to clear (droplets of product should begin to fall out of solution) -> reaction mix is colourless and clear, to all intents & purposes, its appears as water (endpoint of reaction). If batch is not clear continue adding portions of acetone (1 or 2 mls) as above until it is clear, all this signifies is the initial HClO solution is stronger than anticipated.
f) using a sep funnel separate the 2 phases, retaining the lower phase - this being the product
g) Purify and dry resultant product by agitating it gently with a saturated NaCl/bicarb solution and allowing it to stand (in the fridge) for 2 or 3 hours.
h) Separate again, as above, and add 2 or 3 drops of methanol as a preservative. Bottle the finished product and store in a dark place.

Et voila one should have 100 mls of chloroform, chill and serve with your favourite mixer :D

Molecular Manipulations - 25-2-2015 at 11:33

Quote: Originally posted by The Volatile Chemist  
Excess acetone produces 'chlorobutanol'.

Reference please?
Not to nitpick, but I can't see how Chlorobutano, or 1,1,1-Trichloro-2-methyl-2-propanol could be produced without a catalytic base present.

xfusion44 - 28-2-2015 at 02:54

@Buchnerfun

Yes, you added way too much acetone. I didn't do the calculations, but if I remember correctly, I used 27ml of acetone for 2 liters of 5% bleach - you have 10% bleach, so I'd try with 54ml of acetone. Also, I've got milky chloroform a few times, but it wasn't really a problem.

NZniceguy - 27-9-2017 at 01:27

So if I have 2.15 litres of 21.5gm/litre household bleach, what would be the percentage? And can anyone tell me the amount of acetone to add please?
Thanks in advance for any help.

JJay - 27-9-2017 at 02:01

Learning how to do these calculations for yourself is highly encouraged: https://www.youtube.com/watch?v=XnfATaoubzA If you give it a serious attempt, I'll check your answer.

Texium - 27-9-2017 at 06:29

Quote: Originally posted by Molecular Manipulations  
Quote: Originally posted by The Volatile Chemist  
Excess acetone produces 'chlorobutanol'.

Reference please?
Not to nitpick, but I can't see how Chlorobutano, or 1,1,1-Trichloro-2-methyl-2-propanol could be produced without a catalytic base present.
Such as the catalytic base that would be present in hypochlorite bleach?
(Which also contains a fair amount of NaOH)

The Volatile Chemist - 29-9-2017 at 13:40

Lol. Thanks for backing up my 2.5-year old post, zts16.

Not that I have a lot of $ since I'm in college now, but the chloroform prep is on my to-do-soon list, both b/c I want to make 'chlorobutanol' and because now that I have ground glass, having some solvents besides Acetone, n-butyl phthalate, EtOH, and i-PrOH would be nice.

For future reference (for beginning chemists desiring to make chloroform) the Doug's Lab video for this compound is quite useful.

Melgar - 30-9-2017 at 22:12

Quote: Originally posted by Buchnerfun  
Does anyone know an economical way (aside from distillation) to remove acetone from Chloroform?

Why not just get another jug of bleach and add the mixture to that? Turn all your undesired acetone into desired chloroform, while you're at it. That would seem to be the easiest, most practical solution, however adding water and shaking them should also work, since acetone is miscible with water and chloroform is not.

wg48 - 1-10-2017 at 00:17

Quote: Originally posted by zts16  
Quote: Originally posted by Molecular Manipulations  
Quote: Originally posted by The Volatile Chemist  
Excess acetone produces 'chlorobutanol'.

Reference please?
Not to nitpick, but I can't see how Chlorobutano, or 1,1,1-Trichloro-2-methyl-2-propanol could be produced without a catalytic base present.
Such as the catalytic base that would be present in hypochlorite bleach?
(Which also contains a fair amount of NaOH)


If that is correct is there an OTC way of replacing the Cl with H in the chlorobutanol? Zinc, iron or tin in HCl for example.

[Edited on 1-10-2017 by wg48]

XeonTheMGPony - 1-10-2017 at 04:04

https://www.youtube.com/watch?v=SjQG3rKSZUQ Khan acadamy on stoic,,, I like that better

I all so recommend the calcium hypochlorate method as it is much better one IMO less liquid volume, smooth running.

https://erowid.org/archive/rhodium/chemistry/chloroform.html

JJay - 1-10-2017 at 06:10

I've tried using calcium hypochlorite to make chloroform and found it was much easier to use liquid bleach since it doesn't require nearly as much manual shaking ("smooth running" is perhaps the least accurate description I can think of). But unless I can think of another use for it, I'm going to use the rest of my calcium hypochlorite to make chloroform....

Oh and you can remove excess acetone by washing the chloroform with saturated sodium bisulfite or sodium metabisulfite solution, but you'll have to boil the chloroform to make sure it doesn't contain any traces of sulfur dioxide. It's a good idea to distill it anyway.

The Volatile Chemist - 1-10-2017 at 12:07

Quote: Originally posted by wg48  

[...]

If that is correct is there an OTC way of replacing the Cl with H in the chlorobutanol? Zinc, iron or tin in HCl for example.

[Edited on 1-10-2017 by wg48]

Not super likely in a high yield way. You'd be better off looking for ways to chlorinate the ROH group. But I recall Chemplayer's attempt to reduce trichloroacetic acid with some metal powder/HCl method. The idea you propose would probably be similarly messy and give mixed products. But if you wanted to do it, that'd probably be how.

wg48 - 2-10-2017 at 05:02

Quote: Originally posted by The Volatile Chemist  
Quote: Originally posted by wg48  

[...]

If that is correct is there an OTC way of replacing the Cl with H in the chlorobutanol? Zinc, iron or tin in HCl for example.

[Edited on 1-10-2017 by wg48]

Not super likely in a high yield way. You'd be better off looking for ways to chlorinate the ROH group. But I recall Chemplayer's attempt to reduce trichloroacetic acid with some metal powder/HCl method. The idea you propose would probably be similarly messy and give mixed products. But if you wanted to do it, that'd probably be how.


Low yield (say 10%) would not be a big problem as I only need a few grams of butanol to try the low temperature K prep. My research only suggested seriously exotic reagents for example paddlewheel dinuclear molybdenum as hydrodehalogenation catalysts. I will have to try the OTC metal and HCl route but I expect the yield of the full dehaloganated product will be negligible. An other OTCish route may be Raney nickel/Hgas. There is always the Grignard route to a tertiary alcohol.

Why would I want to chlorinate the OH group?