Sciencemadness Discussion Board

Chloroform

JJay - 20-11-2015 at 08:27

Yesterday I made about an ounce of crude chloroform after watching Nile Red's video on YouTube. I simply added 30 mL of acetone to a half gallon of concentrated bleach (8.25% on the label) that had been chilled to -2 C and put in an ice bath. I was a bit surprised to see bubbles when I added the acetone; for some reason I thought the reaction would be much slower... I think using a reflux condenser might improve yields. The bleach turned milky, and after standing overnight, a clear organic bottom layer is visible.

I'm pretty sure that now all I have to do is separate out the organic layer, wash it, dry it and distill to get a small quantity of chloroform.

Detonationology - 20-11-2015 at 08:37

I made a BIG mistake the first time I followed Nile Red's procedure. I added all of the acetone at once (just as he did) and I did not add dropwise. I was very surprised to see that the solution instantly began to boil under it's own heat. Although I was in a ventilated are, I could feel myself getting light headed. Upon examination after the reaction was completed, I realized that nearly all of my chloroform had boiled off. It is possible that you added the acetone too quickly and it boiled off as well. Only one fluid ounce of product seems to be quite a low yield from my experience. If the temperature is maintained during the duration, a reflux is not necessary.

j_sum1 - 20-11-2015 at 17:36

Well, you both did better than my first attempt. I reasoned that the bleach I have available is a bit lower in concentration but I had another hypochlorite source that would work as well. So, being careful with my stoichiometry and the temperature and exothermic nature of the reaction I proceeded. I was hoping to make 100mL of CHCl3 in one hit.
All I really got was an ugly slurry of chloroform and Ca(OH)2 that sunk to the bottom of my containers. For the record, calcium hypochlorite is not an acceptable substitute. And it is really easy to think things through very thoroughly and overlook the obvious.

Texium - 20-11-2015 at 17:55

Couldn't you just filter it out and distill it? If that was the only issue with it, I'd think that would actually be preferable, since excess sodium hydroxide in solution can destroy your chloroform...

Tdep - 20-11-2015 at 18:07

Calcium hydroxide is often a nightmare to deal with, forming sludges rather that fikterable precipitates, but could you perhaps distill it off directly?

gdflp - 20-11-2015 at 18:09

You could also acidify the solution after the reaction is complete to dissolve the Ca(OH)<sub>2</sub> and since the chloroform should be distilled anyway, you can use, for example, hydrochloric acid contaminated with iron.

j_sum1 - 20-11-2015 at 18:10

I figured that with the amount of precipitate and as fine as it was, it would be a real mess to filter. It would have been different if it had settled out into layers. I ended up with a cloudy suspension that took weeks to settle. And there was no clear chloroform layer. Distillation was another option. It seemed easier to simply start again with better reagents.

edit:
I didn't consider acidification. Might be worth a try next time.

[Edited on 21-11-2015 by j_sum1]

JJay - 20-11-2015 at 18:21

I used only a half gallon of bleach, so I think the yield was pretty much inline with what people usually get. I wanted to be sure to have a slight excess of hypochlorite to make sure that all the acetone was consumed.

I added the acetone using a pipette, but I didn't really add it dropwise... the ice bath kept the lower part of of the bleach cool, but the top of the jug reached temperatures in excess of 40 C.

Making chloroform is easy enough that I'm going to pick up some more bleach. I'd like to have enough chloroform to use it for chromatography.

[Edited on 21-11-2015 by JJay]

JJay - 20-11-2015 at 18:51

Quote: Originally posted by j_sum1  
Well, you both did better than my first attempt. I reasoned that the bleach I have available is a bit lower in concentration but I had another hypochlorite source that would work as well. So, being careful with my stoichiometry and the temperature and exothermic nature of the reaction I proceeded. I was hoping to make 100mL of CHCl3 in one hit.
All I really got was an ugly slurry of chloroform and Ca(OH)2 that sunk to the bottom of my containers. For the record, calcium hypochlorite is not an acceptable substitute. And it is really easy to think things through very thoroughly and overlook the obvious.


Using a solid hypochlorite might be a more practical way to produce large quantities of chloroform than using liquid bleach.... I've seen procedures that suggest using 5 gallon buckets filled with ice and powdered pool tablets, but it is so simple and easy to just add a little acetone to a jug of cold bleach....

j_sum1 - 20-11-2015 at 19:14

Hmm. I dissolved the hypochlorite. Therefore the total volume of liquid was quite large.
How would one guarantee complete reaction of the acetone if using a solid hypochlorite?

JJay - 20-11-2015 at 21:22

Quote: Originally posted by j_sum1  
Hmm. I dissolved the hypochlorite. Therefore the total volume of liquid was quite large.
How would one guarantee complete reaction of the acetone if using a solid hypochlorite?


Dissolving may be a good idea... an article quoted in the Rhodium archive suggests making a suspension of calcium hypochlorite in water (from https://www.erowid.org/archive/rhodium/chemistry/chloroform.html):
Quote:

With Calcium Hypochlorite and Acetone

When chlorine is passed into boiling alcohol, both chlorination of the methyl group and oxidation of the primary alcohol group to an aldehyde occur, giving trichloro-acetaldehyde or chloral: When chloral is treated with caustic alkali, fission of the C-C linkage occurs, giving chloroform and a formate. Acetaldehyde and also many ketones, such as acetone, containing the CH3CO- group behave similarly when treated with calcium or sodium hypochlorite, chlorination of the CH3CO- group being immediately followed by fission of the molecule by the alkali present in the hypochlorite solution. The acetone method clearly gives a much cheaper product than the alcohol method.

Required: Calcium Hypochlorite 100g (bleaching powder), acetone 44ml

Place 100g of calcium hypochlorite in a mortar and add 250 ml of water in small quantities at a time: between each addition grind the mixture of bleaching powder and water well together and decant the cream-like suspension through a funnel into a 1-litre flat-bottomed flask. Finally, when all the water has thus been used, only a gritty residue remains in the mortar. Fit the flask with an efficient reflux water-condenser, pour 44ml (35g) of acetone in small quantities, at a time, down the condenser and mix by thorough shaking after each addition. The reaction usually starts spontaneously after a few minutes, and a bath of cold water should be available into which the flask may be dipped if necessary to moderate the reaction. Should the reaction show no signs of starting within 5 minutes of the addition of the acetone, warm the flask cautiously on a boiling water-bath until the reaction starts, and then remove it immediately. When the vigorous boiling has subsided, heat the flask on a boiling water-bath for a further 5-10 minutes (not more) to complete the reaction. Cool the flask in cold water (to prevent loss of chloroform vapour whilst the apparatus is being rearranged) and then fit the flask with a fairly wide delivery-tube and reverse the water-condenser for distillation. Heat the flask on a water-bath until distillation of the chloroform is complete.

The chloroform thus obtained is usually acidic. Therefore shake it thoroughly with dilute sodium hydroxide solution in a separating-funnel. (If the chloroform tends to float on the alkaline solution, it still contains appreciable quantities of acetone: in this case the soda should be run out of the funnel and the chloroform shaken with water to extract the acetone. The extraction with the soda can then be performed after the water has been removed.) Carefully run off the heavy lower layer of chloroform into a small conical flask, dry it over calcium chloride for 15-20 minutes, and then filter it directly into a 75 ml. distilling-flask fitted with a clean dry water-condenser. Distill the chloroform, collecting the fraction of bp. 60-63øC. Yield, 30g. (20ml).

Chloroform is a colourless liquid, of bp 61ø and d 1.50. It has a characteristic sweetish smell, and is frequently used as a solvent in organic chemistry.

Reference: Mann & Saunders, Practical Organic Chemistry, 3rd Ed


Nile Red's technique is so easy that I just picked up two more gallons of concentrated bleach, which are chilling outside in the frigid temperatures. He titrated the bleach before doing the reaction... I haven't bothered since the concentration appears written on the jug, but I wonder if maybe I should since hypochlorite isn't exactly the most stable ion.

[Edited on 21-11-2015 by JJay]

[Edited on 21-11-2015 by JJay]

UC235 - 20-11-2015 at 21:30

Nile Red's technique is just my technique. You're better off with a slight excess of bleach which he doesn't use and assuming the bottle's stated concentration is typically safe. I've noticed lately that many household bleach products are now 8% in my area at least. The exotherm will be correspondingly higher so good pre-cooling is essential.

JJay - 20-11-2015 at 21:52

Quote: Originally posted by UC235  
Nile Red's technique is just my technique. You're better off with a slight excess of bleach which he doesn't use and assuming the bottle's stated concentration is typically safe. I've noticed lately that many household bleach products are now 8% in my area at least. The exotherm will be correspondingly higher so good pre-cooling is essential.


Oh yeah! I see your video here: https://www.youtube.com/watch?v=XYbnNufX5-c I used the same brand of bleach.

JJay - 20-11-2015 at 23:31

I'm not quite sure what the specific gravity of my bleach is just yet, but if I do the stoichometry assuming a specific gravity of 1, it looks like it would take 97.56 mL of 20 C acetone to neutralize a jug of 8.25% bleach (the jugs are slightly under a gallon).

How much excess hypochlorite is a slight excess?

JJay - 21-11-2015 at 04:04

Nobody knows? :) Anyway, the specific gravity of my bleach is 1.083 at 11 C. 104 mL acetone would be about 99% the amount required for neutralizing the hypochlorite if the volume stayed constant with temperature.... It's probably possible to get 3-5% more product than I'm going to get, but since the reagents are cheap and I just need a fixed quantity of chloroform (and I *don't* want any acetone in it), I'm just going to just add 100 mL of acetone to each jug, in 10 mL portions, keeping the temperature below 30 C.

...

When I retrieved the jugs, they were 11 C, and adding 50 mL acetone with stirring following each addition brought the temperatures up to about 25 C. I'm now going to put them back outside to cool down and then add an additional 50 mL to each before isolation/purification and yield calculation.


[Edited on 21-11-2015 by JJay]

BromicAcid - 21-11-2015 at 07:47

JJay, this has all been discussed again, and again, and again. Take the time to read the Garage Experiments with Trichloromethane thread and also work to make your own thread topics more specific.

Here are just two small examples of the pearls contained therein:
Quote: Originally posted by entropy51  
Chloroform

50 gm Ca(OCl)2 and 150 mL H2O was placed in a 1 Liter RBF equipped with magnetic stirring and a reflux condenser and surrounded by a cold (not ice) water bath. 19 mL of acetone was added cautiously, first in 1 mL portions through the condenser until the mixture thickened and foamed. Add remainer of acetone in small portions to maintain a gentle reflux without heating. Finally stir for one hour and arrange condenser for downward distillation. Distill off the CHCl3 using a hot water bath. BP = 60 - 63 C. Yield was about 15 mL.

It is important to use an oversize flask as the reaction foams vigorously.


Quote: Originally posted by BromicAcid  
From 'Thorpe's Dictionary of Applied Chemistry'
Quote:
Manufacture of Chloroform from Acetone and Bleaching-powder.

-This is the process most generally employed. The method differs in minor detail with the various manufactures, but the following may be taken as representatives. The reaction is carried out in a cast-iron still of about 800 gallons capacity, which is provided with stirring gear, steam-coils, and cooling-coils, and is connected with a condenser; 300 gallons of water are run into the still, and 800 lbs of bleaching powder are added through a manhole, which is then securely bolted down. During addition of the bleaching powder the mixture is very thoroughly stirred. (In some processes the mixing is carried out in a separate vessel, and the suspension is strained from the larger unbroken lumps of bleaching powder before being allowed to run into the still.) The container (A in the diagram shown on p. 78) is charged with 70 lb of acetone, which is then slowly run into the bottom of the still by means of a valve B. The introduction of the acetone is accompanied by a rise in the temperature which is not allowed to exceed 110 F., cooling being effected if necessary by stopping the flow of acetone and circulating cold water though the cooling coil in the still. When all the acetone has been introduced the contents of the still are raised to 134 F. At this temperature chloroform begins to distill over. The temperature is then very gradually raised to 150 F., so as to keep the chloroform readily distilling. Towards the end of the reaction the mixture is stirred and the temperature raised until no more chloroform distills over.

The crude chloroform obtained is separated and purified first by agitation with concentrated sulfuric acid. This operation is carried out in the vessel shown in the diagram ; 1,500 lb. of crude chloroform are introduced into the vessel and thoroughly stirred, by means of the agitation gear shown, with 600 lb. of sulfuric acid. The stirring is continued until a sample of the chloroform when thoroughly shaken with pure concentrated sulfuric acid does not impart the slightest color on the latter. The time required for complete purification is usually about 3 hours. The chloroform is next separated from the sulfuric acid and finally distilled over lime. The yield obtained from the above quantities averaged from over 2,000 batches was 124 lb., the highest yield in any one case being 131 lb. Variation in yield is attributed to the varying composition of bleaching powder, though doubtless other factors influence the result. Bleaching powder containing less then 33% of available chlorine gives unsatisfactory results, while samples containing more then 35% of chlorine are also unsatisfactory. The best results appear to be obtained with bleaching powder containing 34% of available chlorine.


I didn’t even know this process was used let alone the main process used in the manufacture of chloroform at one time. I’ve also done some more work with sodium hypochlorite, a mixture of 510 ml 10% NaOCl with 11 ml acetone, providing the reagents are pre-cooled to -10C when allowed to react at these temperatures for an hour give chloroform in an adjusted yield in the 90 percentile range.

[Edited on 12/11/2005 by BromicAcid]


Take some time to research and I guarantee it will save you time and pain on the execution, we're all here to learn and there is a huge trove of knowledge here.

JJay - 21-11-2015 at 09:00

Quote: Originally posted by BromicAcid  
JJay, this has all been discussed again, and again, and again. Take the time to read the Garage Experiments with Trichloromethane thread and also work to make your own thread topics more specific.

Here are just two small examples of the pearls contained therein:

Quote: Originally posted by entropy51  
Chloroform

50 gm Ca(OCl)2 and 150 mL H2O was placed in a 1 Liter RBF equipped with magnetic stirring and a reflux condenser and surrounded by a cold (not ice) water bath. 19 mL of acetone was added cautiously, first in 1 mL portions through the condenser until the mixture thickened and foamed. Add remainer of acetone in small portions to maintain a gentle reflux without heating. Finally stir for one hour and arrange condenser for downward distillation. Distill off the CHCl3 using a hot water bath. BP = 60 - 63 C. Yield was about 15 mL.

It is important to use an oversize flask as the reaction foams vigorously.


Quote: Originally posted by BromicAcid  
From 'Thorpe's Dictionary of Applied Chemistry'
Quote:
Manufacture of Chloroform from Acetone and Bleaching-powder.

-This is the process most generally employed. The method differs in minor detail with the various manufactures, but the following may be taken as representatives. The reaction is carried out in a cast-iron still of about 800 gallons capacity, which is provided with stirring gear, steam-coils, and cooling-coils, and is connected with a condenser; 300 gallons of water are run into the still, and 800 lbs of bleaching powder are added through a manhole, which is then securely bolted down. During addition of the bleaching powder the mixture is very thoroughly stirred. (In some processes the mixing is carried out in a separate vessel, and the suspension is strained from the larger unbroken lumps of bleaching powder before being allowed to run into the still.) The container (A in the diagram shown on p. 78) is charged with 70 lb of acetone, which is then slowly run into the bottom of the still by means of a valve B. The introduction of the acetone is accompanied by a rise in the temperature which is not allowed to exceed 110 F., cooling being effected if necessary by stopping the flow of acetone and circulating cold water though the cooling coil in the still. When all the acetone has been introduced the contents of the still are raised to 134 F. At this temperature chloroform begins to distill over. The temperature is then very gradually raised to 150 F., so as to keep the chloroform readily distilling. Towards the end of the reaction the mixture is stirred and the temperature raised until no more chloroform distills over.

The crude chloroform obtained is separated and purified first by agitation with concentrated sulfuric acid. This operation is carried out in the vessel shown in the diagram ; 1,500 lb. of crude chloroform are introduced into the vessel and thoroughly stirred, by means of the agitation gear shown, with 600 lb. of sulfuric acid. The stirring is continued until a sample of the chloroform when thoroughly shaken with pure concentrated sulfuric acid does not impart the slightest color on the latter. The time required for complete purification is usually about 3 hours. The chloroform is next separated from the sulfuric acid and finally distilled over lime. The yield obtained from the above quantities averaged from over 2,000 batches was 124 lb., the highest yield in any one case being 131 lb. Variation in yield is attributed to the varying composition of bleaching powder, though doubtless other factors influence the result. Bleaching powder containing less then 33% of available chlorine gives unsatisfactory results, while samples containing more then 35% of chlorine are also unsatisfactory. The best results appear to be obtained with bleaching powder containing 34% of available chlorine.


I didn’t even know this process was used let alone the main process used in the manufacture of chloroform at one time. I’ve also done some more work with sodium hypochlorite, a mixture of 510 ml 10% NaOCl with 11 ml acetone, providing the reagents are pre-cooled to -10C when allowed to react at these temperatures for an hour give chloroform in an adjusted yield in the 90 percentile range.

[Edited on 12/11/2005 by BromicAcid]


Take some time to research and I guarantee it will save you time and pain on the execution, we're all here to learn and there is a huge trove of knowledge here.


You stated in that thread that the reaction is best performed using stoichiometric quantities but provided no evidence to back that claim. I'm not saying that I disagree, but I don't see any solid reason to believe it.

BromicAcid - 21-11-2015 at 12:06

Quote: Originally posted by JJay  

You stated in that thread that the reaction is best performed using stoichiometric quantities but provided no evidence to back that claim. I'm not saying that I disagree, but I don't see any solid reason to believe it.


I looked around the thread but did not see where I mentioned that. Please feel free to discuss it in that thread using the 'Quote' button to help things along. I had taken the time to write a detailed reply here but accidentally hit the back button and it was gone so here is a high-level summary.

I wrote in that thread over a decade ago, my discussions here have covered my time in high school, college, and now as an employed chemist. I have been wrong quite a bit but in this case I feel I am correct.

In the event of too much acetone you may form some partially substituted species. This could reduce yield and lead to impurities in the chloroform layer. However I do not think this would be a major issue since the initial substitution is the rate limiting step and subsequent substitutions go faster. Still, excess acetone can dissolve in your chloroform layer leading to loss of purity, as well as in the case of gross excess, difficulties in separating the layers.

Too much hypochlorite can cause additional chlorination of your product causing impurities. The reaction however is not a significant reaction, if it was people would be rejoicing. More concerning with solid hypochlorite would be difficulties with filtration. With liquid hypochlorite would be increased losses due to dissolution in the aqueous phase. With a typical 1 gallon unit of bleach you would expect to lose ~30 grams of chloroform to the aqueous layer based on a solubility of 0.8 g/100 mL so why would you want to add more liquid to the mix?

The reaction is fast, and the elimination of the chloroform drives it forward. There should be no reason to drive it from some other angle. However, that is all on paper. What do they do in industry where cost to value ratio is paramount? Even though this process has been supplanted the quote I provided shows the way this was done back in the day so let's analyze that.

70 lbs acetone = 35751.5 g = 615.55 mol
800 lbs bleaching powder = 362874 g

Regarding bleaching powder (slaked lime, calcium hypochlorite) this has been produced by the same method for quite some time. Basically calcium hydroxide is placed on sheets and gassed with chlorine. The product is a mixture of calcium hypochlorite and calcium chloride and other junk. Pure calcium hypochlorite would be 49.58% active chlorine but the quote says to shoot for 34% chlorine. That is because 34% chlorine is the material of commerce for calcium hypochlorine, both of the past and today, check the link for actual OTC shock that I have in the references section. That is being marketed as 68% and 68% of the 49.58% theoretical gives 33.7% chlorine, just about right on the nose. So let's take the bleaching powder numbers and convert it to calcium hypochlorite.

362874 g bleaching powder x .68 = 276754 g hypochlorite = 1726 mols

This gives a ratio of 2.80 mol hypochlorite for each mol of acetone. so in practice acetone was used in excess at least when using solid hypochlorite.

References:
WALLACH: Ann. 276, 149 (1893).
KOLTHOFF: Pharm. Weekbald 62, 652 (1925).
VAN DER LEE: Chem. Weekblad 23, 444 (1926)
HATCHER AND MEELLER: Trans. Roy. SOC. Can. [3] 23, Sect. 3, 35 (1929)
Pool Shock

JJay - 21-11-2015 at 12:34

Hypochlorite is the more costly component in the reaction, but I think it's better to make acetone the limiting reagent when the priority concern is purity. With excess hypochlorite, carbon tetrachloride should be formed only in minute quantities and should be easy to separate by fractional distillation.

aga - 21-11-2015 at 13:29

Quote: Originally posted by BromicAcid  
Basically calcium hydroxide is placed on sheets and gassed with chlorine.

Whoa hoss !

So NaOHCl can be made by gassing NaOH with Cl2 gas ?

[Edited on 21-11-2015 by aga]

gdflp - 21-11-2015 at 13:38

Yes, by the following reaction :
2NaOH + Cl<sub>2</sub> --> NaOCl + H<sub>2</sub>O + NaCl
It's the best way to produce fresh hypochlorite solutions of a known concentration.(Although actually, the best way is to use hypobromite solutions instead as bromine is much easier to accurately measure.)

EDIT: Equation fixed, apparently I'm quite tired right now.

[Edited on 11-21-2015 by gdflp]

Metacelsus - 21-11-2015 at 13:49

The equation above isn't balanced.

The actual equation is 2 NaOH + Cl2 -> NaCl + NaOCl + H2O

[Edited on 11-21-2015 by Cheddite Cheese]

JJay - 22-11-2015 at 01:28

I have about 200 mL of chloroform now, sitting in a Mason jar under bleach/sodium acetate/sodium hydroxide solution. I have another workup to finish before I distill the chloroform, and I'm sure the yields weren't fantastic, but I am excited to finally have some.

JJay - 23-11-2015 at 06:56

I washed the chloroform with water and then saturated CaCl2 solution and then dried it on CaCl2 and distilled. I got some apparently good quality chloroform, but almost all of the first half of the run was cloudy. It seems awfully wasteful to me to discard almost half of the product, so I'm going to attempt to purify it further and then redistill. Any idea what would make chloroform cloudy?

gdflp - 23-11-2015 at 07:28

That sounds an awful lot like water, I would guess that you used insufficient drying agent. Cloudy distillates such as that typically clear after sitting for a day or two, so if this happens I would dry and redistill.

Camroc37 - 23-11-2015 at 10:10

Quote: Originally posted by j_sum1  
Well, you both did better than my first attempt. I reasoned that the bleach I have available is a bit lower in concentration but I had another hypochlorite source that would work as well. So, being careful with my stoichiometry and the temperature and exothermic nature of the reaction I proceeded. I was hoping to make 100mL of CHCl3 in one hit.
All I really got was an ugly slurry of chloroform and Ca(OH)2 that sunk to the bottom of my containers. For the record, calcium hypochlorite is not an acceptable substitute. And it is really easy to think things through very thoroughly and overlook the obvious.

I got less than 1ml on my first go...

JJay - 23-11-2015 at 10:39

Quote: Originally posted by gdflp  
That sounds an awful lot like water, I would guess that you used insufficient drying agent. Cloudy distillates such as that typically clear after sitting for a day or two, so if this happens I would dry and redistill.


That is exactly what I was thinking... I used quite a bit of drying agent, but it was just tech grade CaCl2 without any special treatment, and I only let it dry for about 20 minutes.

I let it stand overnight on CaCl2, and now I am going to distill again. If that doesn't work, I'll break out the 3A molecular sieves.

JJay - 23-11-2015 at 11:38

So far, the run has been crystal clear from the beginning.

JJay - 23-11-2015 at 13:13

The final yield was 136.7 mL of chloroform from 230.0 mL of acetone, a yield of 54.00%. The purity is probably very good, though the yield was pretty crappy. I stabilized it with 1% ethanol and stored it in an amber glass bottle.

I'm not sure why the yield was so bad, but I definitely noticed a loss of product each time it was washed, and there was also a loss on each distillation.

Dr.Bob - 23-11-2015 at 17:12

A yield of 54% for that prep sounds pretty good to me for such a reaction. You did likely loose some chloroform and acetone on each wash. And distillations lose some each time, it is nearly inevitable, unless you have great equipment and perfect technique.