Chloromethane

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Chloromethane
Stereo, skeletal formula of chloromethane with all explicit hydrogens added
Ball and stick model of chloromethane Spacefill model of chloromethane
Identifiers
CAS number 74-87-3 YesY
PubChem 6327
ChemSpider 6087 YesY
UNII A6R43525YO YesY
EC number 200-817-4
UN number 1063
KEGG C19446 N
MeSH Methyl+Chloride
ChEBI CHEBI:36014 YesY
ChEMBL CHEMBL117545 YesY
RTECS number PA6300000
Beilstein Reference 1696839
Gmelin Reference 24898
Jmol-3D images Image 1
Properties
Molecular formula CH3Cl
Molar mass 50.49 g mol−1
Appearance Colorless gas
Density 1.003 g/mL (-23.8 °C, liquid)[2]2.3065 g/L (0 °C, gas)[2]
Melting point −97.4 °C (−143.3 °F; 175.8 K)[2]
Boiling point −23.8 °C (−10.8 °F; 249.3 K)[2]
Solubility in water 5.325 g L−1
log P 1.113
Vapor pressure 506.09 kPa (at 20.0 °C)
kH 940 nmol Pa−1 kg−1
Structure
Coordination
geometry
Tetragonal
Molecular shape Tetrahedron
Thermochemistry
Std molar
entropy
So298
234.36 J K−1 mol−1
Std enthalpy of
formation
ΔfHo298
−83.68 kJ mol−1
Std enthalpy of
combustion
ΔcHo298
−764.5–−763.5 kJ mol−1
Hazards
MSDS External MSDS
GHS pictograms The flame pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) The health hazard pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word DANGER
GHS hazard statements H220, H351, H373
GHS precautionary statements P210, P281, P410+403
EU Index 602-001-00-7
EU classification Flammable F+ Harmful Xn Toxic T
R-phrases R12, R40, R48/20
S-phrases (S2), S16, S33
NFPA 704
Flammability code 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g., propane Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point −20 °C (−4 °F; 253 K)[2]
Autoignition temperature 625 °C (1,157 °F; 898 K)[2]
Explosive limits 7–19%
LD50 1800 mg/kg (oral, rat)[2]
5.3 mg/L/4 h (inhalation, rat)[2]
Related compounds
Related alkanes
Related compounds 2-Chloroethanol
Supplementary data page
Structure and
properties
n, εr, etc.
Thermodynamic
data
Phase behaviour
Solid, liquid, gas
Spectral data UV, IR, NMR, MS
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
Infobox references

Chloromethane, also called methyl chloride, R-40 or HCC 40, is a chemical compound of the group of organic compounds called haloalkanes. It was once widely used as a refrigerant. It is a colorless extremely flammable gas with a mildly sweet odor, which is, however, detected at possibly toxic levels. Due to concerns about its toxicity, it is no longer present in consumer products. Chloromethane 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.

Occurrence[edit]

Chloromethane is the most abundant organohalogen, anthropogenic or natural, in the atmosphere.

Marine[edit]

Laboratory cultures of marine phytoplankton (Phaeodactylum tricornutum, Phaeocystis sp., Thalassiosira weissflogii, Chaetoceros calcitrans, Isochrysis sp., Porphyridium sp., Synechococcus sp., Tetraselmis sp., Prorocentrum sp., and Emiliana huxleyi) produce CH3Cl, but in relatively insignificant amounts.[3][4] An extensive study of 30 species of polar macroalgae revealed the release of significant amounts of CH3Cl in only Gigartina skottsbergii and Gymnogongrus antarcticus.[5]

Biogenesis[edit]

The salt marsh plant Batis maritima contains the enzyme methyl chloride transferase that catalyzes the synthesis of CH3Cl from S-adenosine-L-methionine and chloride.[6] This protein has been purified and expressed in E. coli, and seems to be present in other organisms such as white rot fungi (Phellinus pomaceus), red algae (Endocladia muricata), and the ice plant (Mesembryanthemum crystallium), each of which is a known CH3Cl producer.[6][7]

Production[edit]

Large amounts of chloromethane are produced naturally in the oceans by the action of sunlight on biomass and chlorine in sea foam. However, all chloromethane that is used in industry is produced synthetically.

Most chloromethane is prepared by reacting methanol with hydrogen chloride, according to the chemical equation

CH3OH + HCl → CH3Cl + H2O

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 chloromethane 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.

Further reaction of chloromethane with chlorine can produce dichloromethane, trichloromethane (known as chloroform) and tetrachloromethane (also known as carbon tetrachloride).

Uses[edit]

Chloromethane was a widely used refrigerant, but its use has been discontinued due to its toxicity and flammability. Chloromethane was also once used for producing lead-based gasoline additives (tetramethyllead).

The most important use of chloromethane today is as a chemical intermediate in the production of silicone polymers. Smaller quantities are used as a solvent in the manufacture of butyl rubber and in petroleum refining.

Chloromethane is employed as a methylating and chlorinating agent in organic chemistry. It is also used in a variety of other fields: as an extractant for greases oils and resins, as a propellant and blowing agent in polystyrene foam production, as a local anesthetic, as an intermediate in drug manufacturing, as a catalyst carrier in low-temperature polymerization, as a fluid for thermometric and thermostatic equipment, and as a herbicide.

Safety[edit]

Inhalation of chloromethane gas produces central nervous system effects similar to drug intoxication. Exposure may cause drowsiness, dizziness, or confusion and difficulty breathing, walking or speaking may occur. At higher concentrations, paralysis, seizures, and coma can result.

In case of ingestion, nausea and vomiting may occur. Skin contact, when in the form of a refrigerated liquid, may result in frostbite. Contact with the eyes may result in dim vision, and widely dilated pupils that react slowly to changes in light.

Chronic exposure to chloromethane has been linked to birth defects in mice. In humans, exposure to chloromethane during pregnancy may cause the fetus' lower spinal column, pelvis, and legs to form incorrectly, but this has not been conclusively demonstrated.

In 1997, a re-investigation of Boston's Cocoanut Grove nightclub fire in 1942 cited a chloromethane leak from a refrigerator as a major cause of that disaster.

References[edit]

  1. ^ "Methyl Chloride - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 26 March 2005. Retrieved 23 June 2012. 
  2. ^ a b c d e f g h i j k l m Record in the GESTIS Substance Database from the IFA
  3. ^ Scarratt MG, Moore RM (1996). "Production of Methyl Chloride and Methyl Bromide in Laboratory Cultures of Marine Phytoplankton". Mar Chem 54 (3–4): 263. doi:10.1016/0304-4203(96)00036-9. 
  4. ^ Scarratt MG, Moore RM (1998). "Production of Methyl Bromide and Methyl Chloride in Laboratory Cultures of Marine Phytoplankton II". Mar Chem 59 (3–4): 311. doi:10.1016/S0304-4203(97)00092-3. 
  5. ^ Laturnus F (2001). "Marine Macroalgae in Polar Regions as Natural Sources for Volatile Organohalogens". Environ Sci Pollut Res 8 (2): 103. doi:10.1007/BF02987302. 
  6. ^ a b Ni X, Hager LP (1998). "cDNA Cloning of Batis maritima Methyl Chloride Transferase and Purification of the Enzyme". Proc Natl Acad Sci USA 95 (22): 12866–71. doi:10.1073/pnas.95.22.12866. PMC 23635. PMID 9789006. 
  7. ^ Ni X, Hager LP (1999). "Expression of Batis maritima Methyl Chloride Transferase in Escherichia coli". Proc Natl Acad Sci USA 96 (7): 3611–5. doi:10.1073/pnas.96.7.3611. PMC 22342. PMID 10097085. 

External links[edit]