Trichloromethane

 

Trichloromethane

Chemical formula	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 (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

   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

   4 CH₄ + 10 Cl₂

   {400 -500 °C

   →

   }

   CH₃Cl + CH₂Cl₂ + CHCl₃ + CCl₄ + 10 HCl

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

   4 CH₄ + 10 Cl₂

   {hv

   →

   }

   CH₃Cl + CH₂Cl₂ + CHCl₃ + CCl₄ + 10 HCl

Purification

Fractionally distill the product mixture

Chloromethane boiling points

Compound	Boiling point (°C)
CH3Cl	-23.8
CH2Cl2	39.6
CHCl3	61.15
CCl4	76.72

Rectification

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

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

   COCl₂ + H₂O → CO₂ + HCl

   2 HCl + Na₂CO₃ → 2 NaCl + 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

• Store with 1% by mass ethanol, removing any produced dichlorocarbonyl as diethyl carbonate

See Also

• chloromethane, dichloromethane, carbon tetrachloride