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Saturday, August 24, 2013

Synthesis of Chloroform from Acetone and Bleach - Haloform Reaction - Lu Le Laboratory



Chloroform is an organic compound with formula CHCl3. It is one of the four chloromethanes. The colorless, sweet-smelling, dense liquid is a trihalomethane, and is considered somewhat hazardous. Several million tons are produced annually as a precursor to PTFE and refrigerants, but its use for refrigerants is being phased out.

 
During prolonged storage in the presence of oxygen, chloroform converts slowly to phosgene, releasing HCl in the process. To prevent accidents, commercial chloroform is stabilized with ethanol or amylene, but samples that have been recovered or dried no longer contain any stabilizer. Amylene has been found ineffective, and the phosgene can affect analytes in samples, lipids, and nucleic acids dissolved in or extracted with chloroform. Dissolved phosgene cannot be removed by distillation or carbon filters, but it is removed by calcium hydroxide or activated alumina. Phosgene and HCl can be removed from chloroform by washing with saturated aqueous carbonate solutions, such as sodium bicarbonate. This procedure is simple and results in harmless products. Phosgene reacts with water to form carbon dioxide and HCl, and the carbonate salt neutralizes the resulting acid.  (Wikipedia)

To prepare chloroform easily, using acetone and bleach to generate a haloform reaction may be a good method. The equation and mechanism is shown below.

Reaction Equation
 


Mechanism
 


Chemicals

1.     Acetone: 36.1536 g
2.     12% sodium hypochlorite (or industrial bleach): 1000.0 mL 
 


3.     Magnesium sulfite anhydrous: Amount

Procedure

1.     Add 1000.0 mL filtered 12% sodium hypochlorite in a serum bottle.[1]
 


2.     Chill the bottle containing with 12% NaOCl(aq) in an ice bath.[2]
 




3.     Add 36.1536 g of acetone into the bottle slowly.
 


4.     Stir the mixture thoroughly and incubate on ice for 1~2 hours.
 




5.     Collect the lower layer.




6.     Dry the crude product with magnesium sulfate anhydrous.
 


7.     Distill the dried product and collect the distillate at 61~62.
 




 My fluid cooling system

8.     Dry the product again with magnesium sulfate anhydrous.
 



 
9.     Figure out the yield of chloroform.
10.  Preserve the product in a brown glass bottle.




Notes

[1] There may have some precipitate in the bottom of the bottle of industrial bleach. That is because sodium hypochlorite may disproportionate at room temperature and produce sodium chloride and sodium chlorate, and the solubility of sodium chloride is the worst in these three salts. So the NaCl will salt out and form precipitate.

[2] Haloform reaction is an exothermic reaction so the temperature of the mixture would raise high (about 70) if cooling is not sufficient. High temperature may lead side reaction occur:

3 ClO-(aq) ClO3-(aq) + 2 Cl-(aq)

This side reaction may reduce the concentration of hypochlorite ion and cause decrease in the yield. So it is important in controlling the temperature of the reactant.

Report Sheet

Volume of 12% sodium hypochlorite
1000.0 mL
Density of 12% sodium hypochlorite (24.0)

Test 1
1.1557 g/mL
Test 2
1.1618 g/mL
Average
1.1586 g/mL
Mole of sodium hypochlorite
1.8675 mol
Weight of acetone
36.1536 g

= 0.6225 mol
Theoretical weight of chloroform
74.2980 g
Weight of Chloroform
34.6337 g
Yield
46.61%


1 comment:

  1. imma try this at home for research purposes

    ReplyDelete