Trichloromethane

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Trichloromethane
Chemical formula {{#Chem:CHCl3}}
OTP appearance clear liquid 
Molar Mass(g/mol) 119.38 
Density(g/cc) 1.489 
Melting Point(°C) −63.5 
Boiling Point(°C) 61.15 
Solubility in water(g/L) insoluble
NFPA 704
0
2
0
 

Uses

Justification Questioned

Other

  • Solvent
  • Reagent
  • Precursor to many other compounds including TFE
  • General anesthetic
  • Precursor to DCM ({{#Chem: CHCl3 + Zn + HCl = CH2Cl2 + ZnCl2 }}).

Natural occurrence

None.

Hazards

  • CNS depressant
  • Decomposes with oxygen into toxic byproducts

Production

Synthesis

From propanone

  1. Combine sodium hypochlorite and propanone producing a variety of compounds
    {{#Chem: 3 NaOCl + (CH3)2CO = CH3COONa + 2 NaOH + CHCl3 }}
  2. Pour off and discard the supernatant (water, sodium hydroxide, sodium acetate, sodium hypochlorite)
  3. The lower layer is mostly trichloromethane with some water.
  4. Chemically dry the trichloromethane over dried magnesium sulfate or calcium chloride

From methane

cf. chloromethane production
thermal conversion
  1. Mix methane and chlorine gasses
  2. Heat to temperatures yielding hydrochloric acid and a variety of chlorine-substituted methane compounds
    {{#Chem: 4CH4 + 10Cl2 { 400-500° C = } CH3Cl + CH2Cl2 + CHCl3 + CCl4 + 10HCl }}
ultraviolet conversion
  1. Mix methane and chlorine gasses
  2. Expose to ultraviolet light, cleaving the chlorine and initiating reactions yielding a variety of chlorine-substituted methane compounds
    {{#Chem: 4CH4 + 10Cl2 { hv = } CH3Cl + CH2Cl2 + CHCl3 + CCl4 + 10HCl }}

Purification

Fractionally distill the product mixture

Chloromethane boiling points
Compound Boiling point (°C)
{{#Chem:CH3Cl}} -23.8
{{#Chem:CH2Cl2}} 39.6
{{#Chem:CHCl3}} 61.15
{{#Chem:CCl4}} 76.72

Rectification

Trichloromethane catalytically decomposes (in the presence of) oxygen into toxic byproducts:

{{#Chem: 2 CHCl3 + O2 = 2 COCl2 + 2 HCl}}

This can be addressed as follows:

  1. Prepare a saturated solution of sodium carbonate or sodium bicarbonate
  2. Combine this with the trichloromethane
    {{#Chem: COCl2 + H2O = CO2 + HCl}}
    {{#Chem: 2HCl + Na2CO3 = 2NaCl + CO2 + H2O }}
  3. Agitate
  4. Let stand
  5. Pour off the supernatant
  6. Filter
  7. Discard the residue
  8. Chemically dry the filtrate yielding rectified trichloromethane

Storage

Disposal

See Also

References