Chemical Fact Sheet

Chemical Abstract Number (CAS #) 74884
CASRN 74-88-4
Methyl iodide
Methane, iodo
Analytical Methods EPA Method 524.2
EPA Method 8010
EPA Method 8260
Molecular FormulaCH3I

Link to the National Library of Medicine's Hazardous Substances
Database for more details on this compound.

Use IN METHYLATIONS; IN MICROSCOPY BECAUSE OF HIGH REFRACTIVE INDEX; AS IMBEDDING MATERIAL FOR EXAMINING DIATOMS; IN TESTING FOR PYRIDINE USED AS METHYLATING AGENT IN PREPN OF PHARMACEUTICAL INTERMEDIATES CHEM INTERMED FOR METHYLAMINES & QUATERNARY AMMONIUM IODIDES CHEM INTERMED FOR QUATERNARY PHOSPHONIUM IODIDES CHEM INTERMED FOR ORGANOMETALLICS, EG, METHYL MERCURIC IODIDE Used as a fire extinguisher . Methyl iodide has been investigated in India for use as a fumigant to control internal fungi of grain sorghum. REACTS WITH MANY CMPD AS ALKYLATING AGENT Used as building block for radioactive tracers synthesis. Methyl iodide (14C) is used for carbon-14-labeled compounds methyl iodide (3H) is used for tritium-labeled compounds p.634] Reacts with dimethyl ethyl amine to yield quaternary ammonium compounds
Boiling Point 42.5 DEG C
Melting Point -66.5 DEG C
Molecular Weight 141.94
Density 2.28 @ 20 DEG C/4 DEG C
Sensitivity Data Eye irritant; can blister the skin. Lung irritation from acute exposure. Prolonged contact with skin can cause vesicant burns.
Environmental Impact Methyl iodide is produced by many marine photosynthetic organisms and therefore the surface ocean is thought to be a major natural source of methyl iodide. Some of this will exchange into the atmosphere and some will react with seawater (half-life approximately 20 days at 19 deg C) to form methyl chloride. It will not be expected to sorb to soil or sediment, or to bioconcentrate in aquatic organisms; however, there is some evidence of bioaccumulation in marine animals. In the atmosphere, methyl iodide degrades (half-life 3-7 hr). Humans are exposed to methyl iodide from the ambient air and from ingesting seafood from the ocean. .
Environmental Fate TERRESTRIAL FATE: If spilled on land, methyl iodide would be expected to volatize rapidly. It will not be expected to sorb to soils. No studies could be found concerning its fate on land but it could photolyze or decompose by reacting with chlorides. AQUATIC FATE: Methyl iodide will be removed from the water by volatilization (half-life 3.6 hr in a typical river). In the ocean methyl iodide will react with chloride to form methyl chloride (methyl iodide half-life 20 and 58 days at 19.2 and 10.8 deg C, respectively). In placid bodies of fresh water, hydrolysis of methyl iodide may be significant (half-life 100-251 days). Photolysis may also be important but there is no data with which to evaluate its extent. It will not be expected to bind to sediments or to bioconcentrate in aquatic organisms; however, there is some evidence of bioaccumulation in marine animals. ATMOSPHERIC FATE: Methyl iodide photolyzes in air with a half-life of 7 hr and less under smog situations. Aquatic Fate: In seawater, iodomethane can react with chloride ion to yield chloromethane, and this reaction occurs as fast as the exchange of iodomethane into the atmosphere (exchange rate, 4x10-7/sec). The monohalomethanes are not oxidized readily under ordinary conditions. Atmospheric Fate: Monohalomethanes undergo photolysis in the upper atmosphere where ultraviolet radiation is of sufficient energy to initiate a reaction. Monohalomethanes
Drinking Water Impact SEAWATER: Point Reyes, CA - nearshore 37 parts/trillion . Atlantic Ocean surface water 135 parts/trillion .

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