Science Fair Project Encyclopedia
Chloromethane
|
General |
|
|---|---|
| Name | Methyl chloride |
| Chemical formula | CH3Cl |
| Appearance | Colorless gas |
|
Physical |
|
| Formula weight | 50.5 amu |
| Melting point | 175 K (-98 °C) |
| Boiling point | 249 K (-24 °C) |
| Density | 0.92 ×103 kg/m3 (liquid) |
| Solubility | slightly soluble in water |
|
Thermochemistry |
|
| ΔfH0gas | -81.9 kJ/mol |
| ΔfH0liquid | ? kJ/mol |
| ΔfH0solid | ? kJ/mol |
| S0gas, 1 bar | ? J/mol·K |
| S0liquid, 1 bar | ? J/mol·K |
| S0solid | ? J/mol·K |
|
Safety | |
| Ingestion | Causes nausea and vomiting. |
| Inhalation | May cause difficulty breathing, with gasping and choking. |
| Skin | As a refrigerated liquid, may result in frostbite. |
| Eyes | May result in dim vision, widely dilated pupils that react slowly to changes in light. |
| More info | Hazardous Chemical Database |
|
SI units were used where possible. Unless otherwise stated, standard conditions were used. | |
Chloromethane or Methyl chloride is a chemical compound once widely used as a refrigerant. It is a colorless flammable gas with a slightly sweet odor. Due to concerns about its toxicity, it is no longer present in consumer products.
Methyl chloride was first synthesized by the French chemists Jean-Baptiste Dumas and Eugene Peligot in 1835 by boiling a mixture of methanol, sulfuric acid, and sodium chloride. This method is similar to that used today.
Production
Large amounts of methyl chloride are produced naturally in the oceans by the action of sunlight on biomass and chlorine in sea foam. However, all methyl chloride that is used in industry is produced synthetically.
Most methyl chloride is prepared by reacting methanol with hydrogen chloride, according to the chemical equation
This can be carried out either by bubbling hydrogen chloride gas through boiling methanol with or without a zinc chloride catalyst, or by passing combined methanol and hydrogen chloride vapors over an alumina catalyst at 350°C.
A smaller amount of methyl chloride is produced by heating a mixture of methane and chlorine to over 400°C. However, this method also results in more highly chlorinated compounds such as methylene chloride and chloroform and is usually only used when these other products are also desired.
Uses
Formerly, methyl chloride was a widely used refrigerant, but due to its toxicity this use has been discontinued. Methyl chloride was also once used for producing lead-based additives for gasoline, but leaded gasoline has been phased out in most of the industrialized world (an important exception being the former Soviet Union).
The most important use of methyl chloride today is as an chemical intermediate is the production of silicone polymers. Smaller quantities are used in the manufacture of artificial rubber.
Safety
Inhalation of methyl chloride gas produces central nervous system effects similar to intoxication. Victims may feel drowsy, dizzy, or confused, and have difficulty walking or speaking. At higher concentrations, paralysis, seizures, and coma may result.
Chronic exposure to methyl chloride has been linked to birth defects in mice. In humans, exposure to methyl chloride during pregnancy may cause the fetus' lower spinal column, pelvis, and legs to form incorrectly, but this has not been conclusively proven.
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