Iodomethane
Overview
 
Methyl iodide, also called iodomethane, and commonly abbreviated "MeI", is the chemical compound
Organoiodine compound
Organoiodine compounds are organic compounds that contain one or more carbon–iodine bonds. They occur widely in organic chemistry, but are relatively rare in nature...

 with the formula CH3I. It is a dense
Density
The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...

, colorless, volatile
Vapor pressure
Vapor pressure or equilibrium vapor pressure is the pressure of a vapor in thermodynamic equilibrium with its condensed phases in a closed system. All liquids have a tendency to evaporate, and some solids can sublimate into a gaseous form...

 liquid. In terms of chemical structure, it is related to methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

 by replacement of one hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 atom by an atom of iodine
Iodine
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....

. It is naturally emitted by rice
Rice
Rice is the seed of the monocot plants Oryza sativa or Oryza glaberrima . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies...

 plantations in small amounts. It is also produced in vast quantities estimated to be greater than 214,000 tons annually by algae and kelp in the world's temperate oceans and in lesser amounts on land due to terrestrial fungi and bacteria.
Encyclopedia
Methyl iodide, also called iodomethane, and commonly abbreviated "MeI", is the chemical compound
Organoiodine compound
Organoiodine compounds are organic compounds that contain one or more carbon–iodine bonds. They occur widely in organic chemistry, but are relatively rare in nature...

 with the formula CH3I. It is a dense
Density
The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...

, colorless, volatile
Vapor pressure
Vapor pressure or equilibrium vapor pressure is the pressure of a vapor in thermodynamic equilibrium with its condensed phases in a closed system. All liquids have a tendency to evaporate, and some solids can sublimate into a gaseous form...

 liquid. In terms of chemical structure, it is related to methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

 by replacement of one hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 atom by an atom of iodine
Iodine
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....

. It is naturally emitted by rice
Rice
Rice is the seed of the monocot plants Oryza sativa or Oryza glaberrima . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies...

 plantations in small amounts. It is also produced in vast quantities estimated to be greater than 214,000 tons annually by algae and kelp in the world's temperate oceans and in lesser amounts on land due to terrestrial fungi and bacteria. Methyl iodide is used in organic synthesis
Organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...

 as a source of methyl group
Methyl group
Methyl group is a functional group derived from methane, containing one carbon atom bonded to three hydrogen atoms —CH3. The group is often abbreviated Me. Such hydrocarbon groups occur in many organic compounds. The methyl group can be found in three forms: anion, cation and radical. The anion...

s, and was approved for use as a pesticide
Pesticide
Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...

 by the United States Environmental Protection Agency
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...

 in 2007. Iodomethane is a pre-plant biocide used to control insects, plant parasitic nematodes, soil borne pathogens, and weed seeds. The compound is registered for use as a preplant soil treatment for field grown strawberries, peppers, tomatoes, stone fruits, tree nuts, grape vines, ornamentals and turf and nursery grown strawberries, stone fruits, tree nuts, and conifer trees.

Preparation and handling

Methyl iodide is formed via the exothermic reaction
Exothermic reaction
An exothermic reaction is a chemical reaction that releases energy in the form of light or heat. It is the opposite of an endothermic reaction. Expressed in a chemical equation:-Overview:...

 that occurs when iodine
Iodine
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....

 is added to a mixture of methanol
Methanol
Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...

 with red phosphorus
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...

. The iodinating reagent is phosphorus triiodide
Phosphorus triiodide
Phosphorus triiodide is an unstable red solid which reacts violently with water. It is a common misconception that PI3 is too unstable to be stored; it is, in fact, commercially available. It is widely used in organic chemistry for converting alcohols to alkyl iodides. It is also a powerful...

 that is formed in situ:
3 CH3OH
Methanol
Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...

  + PI3 → 3 CH3I + H3PO3
Phosphorous acid
Phosphorous acid is the compound described by the formula H3PO3. This acid is diprotic , not triprotic as might be suggested by this formula. Phosphorous acid is as an intermediate in the preparation of other phosphorus compounds.-Nomenclature and tautomerism:H3PO3 is more clearly described with...



Alternatively, it is prepared from the reaction of dimethyl sulfate
Dimethyl sulfate
Dimethyl sulfate is a chemical compound with formula 2SO2. As the diester of methanol and sulfuric acid, its formula is often written as 2SO4 or even Me2SO4, where CH3 or Me is methyl...

 with potassium iodide in the presence of calcium carbonate
Calcium carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...

:
(CH3O)2SO2
Dimethyl sulfate
Dimethyl sulfate is a chemical compound with formula 2SO2. As the diester of methanol and sulfuric acid, its formula is often written as 2SO4 or even Me2SO4, where CH3 or Me is methyl...

  + KI
Potassium iodide
Potassium iodide is an inorganic compound with the chemical formula KI. This white salt is the most commercially significant iodide compound, with approximately 37,000 tons produced in 1985. It is less hygroscopic than sodium iodide, making it easier to work with...

  → CH3I + CH3OSO2OK


Methyl iodide can also be prepared by the reaction of methanol with potassium iodide, catalyzed by acid:
CH3OH + KI + H2SO4 → CH3I + K2SO4 + H2O

The reaction is carried out at low temperature and the water generated in the reaction is trapped by excess sulfuric acid so the reaction is not reversible. The generated methyl iodide can be distilled from the reaction mixture.

Storage and purification

Like many organoiodide compounds, methyl iodide is typically stored in dark bottles to inhibit degradation cause by light to give iodine, giving degraded samples a purplish tinge. Commercial samples may be stabilized by copper or silver wire. It can be purified by distillation followed by washing with Na2S2O3
Sodium thiosulfate
Sodium thiosulfate , also spelled sodium thiosulphate, is a colorless crystalline compound that is more familiar as the pentahydrate, Na2S2O3•5H2O, an efflorescent, monoclinic crystalline substance also called sodium hyposulfite or “hypo.”...

 to remove iodine.

Methylation reagent

Methyl iodide is an excellent substrate for SN2 substitution reactions. It is sterically
Steric effects
Steric effects arise from the fact that each atom within a molecule occupies a certain amount of space. If atoms are brought too close together, there is an associated cost in energy due to overlapping electron clouds , and this may affect the molecule's preferred shape and reactivity.-Steric...

 open for attack by nucleophile
Nucleophile
A nucleophile is a species that donates an electron-pair to an electrophile to form a chemical bond in a reaction. All molecules or ions with a free pair of electrons can act as nucleophiles. Because nucleophiles donate electrons, they are by definition Lewis bases.Nucleophilic describes the...

s, and iodide
Iodide
An iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. This page is for the iodide ion and its salts. For information on organoiodides, see organohalides. In everyday life, iodide is most commonly encountered as a component of iodized salt,...

 is a good leaving group
Leaving group
In chemistry, a leaving group is a molecular fragment that departs with a pair of electrons in heterolytic bond cleavage. Leaving groups can be anions or neutral molecules. Common anionic leaving groups are halides such as Cl−, Br−, and I−, and sulfonate esters, such as para-toluenesulfonate...

. It is used for alkylating carbon, oxygen, sulfur, nitrogen, and phosphorus nucleophiles. Unfortunately, it has a high equivalent weight: one mole of methyl iodide weighs almost three times as much as one mole of methyl chloride
Chloromethane
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 minorly sweet odor, which is, however, detected at possibly toxic levels...

. On the other hand, methyl chloride and methyl bromide are gaseous, thus harder to handle; they are also weaker alkylating agents.

Iodides are generally expensive relative to the more common chlorides and bromides, though methyl iodide is reasonably affordable; on a commercial scale, the more toxic dimethyl sulfate
Dimethyl sulfate
Dimethyl sulfate is a chemical compound with formula 2SO2. As the diester of methanol and sulfuric acid, its formula is often written as 2SO4 or even Me2SO4, where CH3 or Me is methyl...

 is preferred, since it is both cheap and liquid. The iodide leaving group in methyl iodide may cause side reactions, as it is a powerful nucleophile. Finally, being highly reactive, methyl iodide is more dangerous for laboratory workers than related chlorides and bromides.

For example, it can be used for the methylation of carboxylic acid
Carboxylic acid
Carboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group...

s or phenol
Phenol
Phenol, also known as carbolic acid, phenic acid, is an organic compound with the chemical formula C6H5OH. It is a white crystalline solid. The molecule consists of a phenyl , bonded to a hydroxyl group. It is produced on a large scale as a precursor to many materials and useful compounds...

s:


In these examples, the base
Base (chemistry)
For the term in genetics, see base A base in chemistry is a substance that can accept hydrogen ions or more generally, donate electron pairs. A soluble base is referred to as an alkali if it contains and releases hydroxide ions quantitatively...

 (K2CO3
Potassium carbonate
Potassium carbonate is a white salt, soluble in water , which forms a strongly alkaline solution. It can be made as the product of potassium hydroxide's absorbent reaction with carbon dioxide. It is deliquescent, often appearing a damp or wet solid...

 or Li2CO3
Lithium carbonate
Lithium carbonate is a chemical compound of lithium, carbon, and oxygen with the formula Li2CO3. This colorless salt is widely used in the processing of metal oxides and has received attention for its use in psychiatry. It is found in nature as the rare mineral zabuyelite.-Properties:Like almost...

) removes the acidic proton to form the carboxylate or phenoxide anion, which serves as the nucleophile in the SN2 substitution.

Iodide is a "soft" anion which means that methylation with MeI tends to occur at the "softer" end of an ambidentate nucleophile
Nucleophile
A nucleophile is a species that donates an electron-pair to an electrophile to form a chemical bond in a reaction. All molecules or ions with a free pair of electrons can act as nucleophiles. Because nucleophiles donate electrons, they are by definition Lewis bases.Nucleophilic describes the...

. For example, reaction with thiocyanate
Thiocyanate
Thiocyanate is the anion [SCN]−. It is the conjugate base of thiocyanic acid. Common derivatives include the colourless salts potassium thiocyanate and sodium thiocyanate. Organic compounds containing the functional group SCN are also called thiocyanates...

 ion favours attack at rather than "hard" , leading mainly to methyl thiocyanate
Methyl thiocyanate
Methyl thiocyanate is a chemical compound that is listed as a extremely hazardous substances by the United States's Emergency Planning and Community Right-to-Know Act....

 (CH3SCN) rather than CH3NCS. This behavior is relevant to the methylation of stabilized enolates such as those derived from 1,3-dicarbonyl compounds. Methylation of these and related enolates can occur on the harder oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 atom or the (usually desired) carbon atom. With methyl iodide, C-alkylation nearly always predominates.

Other reactions

In the Monsanto process
Monsanto process
The Monsanto process is an important method for the manufacture of acetic acid by catalytic carbonylation of methanol. This process operates at a pressure of 30–60 atm and a temperature of 150–200 °C and gives a selectivity greater than 99%. It was developed 1960 by German BASF and...

, MeI forms in situ from the reaction of methanol
Methanol
Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...

 and hydrogen iodide
Hydrogen iodide
Hydrogen iodide is a diatomic molecule. Aqueous solutions of HI are known as iohydroic acid or hydroiodic acid, a strong acid. Gas and aqueous solution are interconvertible...

. The CH3I then reacts with carbon monoxide
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...

 in the presence of a rhodium
Rhodium
Rhodium is a chemical element that is a rare, silvery-white, hard and chemically inert transition metal and a member of the platinum group. It has the chemical symbol Rh and atomic number 45. It is composed of only one isotope, 103Rh. Naturally occurring rhodium is found as the free metal, alloyed...

 complex to form acetyl iodide
Acetyl iodide
Acetyl iodide is an organoiodine compound wth the formula CH3CI. It is a colourless liquid. It is formally derived from acetic acid. Although far rarer in the laboratory than the related acetyl bromide and acetyl chloride, acetyl iodide is produced, transiently at least, on a far larger scale...

, the precursor to acetic acid
Acetic acid
Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...

 after hydrolysis
Hydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...

. Most acetic acid is prepared by this method.

MeI is used to prepare the Grignard reagent, methylmagnesium iodide ("MeMgI"), a common source of "Me. The use of MeMgI has been somewhat superseded by the commercially available methyllithium. MeI can also be used to prepare dimethylmercury
Dimethylmercury
Dimethylmercury is an organomercury compound. This colorless liquid is one of the strongest known neurotoxins. It is described as having a slightly sweet smell, although inhaling enough vapor to detect its odor would be hazardous....

, by reacting 2 moles of MeI with a 2/1-molar sodium amalgam
Amalgam
Amalgam may refer to:* Amalgam , mercury alloy* Amalgam , material of "silver" tooth fillings* Amalgam Comics, publisher* Amalgam, Gauteng, South Africa* Amalgam , fictional character in the Marvel Universe...

 (2 moles of sodium, 1 mol of mercury).

Use as a pesticide

Methyl iodide has also been proposed for use as a fungicide
Fungicide
Fungicides are chemical compounds or biological organisms used to kill or inhibit fungi or fungal spores. Fungi can cause serious damage in agriculture, resulting in critical losses of yield, quality and profit. Fungicides are used both in agriculture and to fight fungal infections in animals...

, herbicide
Herbicide
Herbicides, also commonly known as weedkillers, are pesticides used to kill unwanted plants. Selective herbicides kill specific targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic "imitations" of plant...

, insecticide
Insecticide
An insecticide is a pesticide used against insects. They include ovicides and larvicides used against the eggs and larvae of insects respectively. Insecticides are used in agriculture, medicine, industry and the household. The use of insecticides is believed to be one of the major factors behind...

, nematicide
Nematicide
A nematicide is a type of chemical pesticide used to kill parasitic nematodes.One common nematicide is obtained from neem cake, the residue obtained after cold-pressing the fruit and kernels of the neem tree. Known by several names in the world, the tree was first cultivated in India in ancient...

, and as a soil disinfectant, replacing methyl bromide (also known as bromomethane) (banned under the Montreal Protocol
Montreal Protocol
The Montreal Protocol on Substances That Deplete the Ozone Layer is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances believed to be responsible for ozone depletion...

). Manufactured by Arysta LifeScience and sold under the brand name MIDAS, methyl iodide is registered as a pesticide in the U.S., Mexico, Morocco, Japan, Turkey, and New Zealand and registration is pending in Australia, Guatemala, Costa Rica, Chile, Egypt, Israel, South Africa and other countries. In September 2007, 54 chemists and physicians contacted the EPA expressing deep concerns of serious risk if methyl iodide were to be permitted for use in agriculture. In a letter to the EPA they stated: "We are skeptical of U.S. EPA’s conclusion that the high levels of exposure to methyl iodide that are likely to result from broadcast applications are “acceptable” risks. U.S. EPA has made many assumptions about toxicology and exposure in the risk assessment that have not been examined by independent scientific peer reviewers for adequacy or accuracy. Additionally, none of U.S. EPA’s calculations account for the extra vulnerability of the unborn fetus and children to toxic insults." EPA Assistant Administrator Jim Gulliford replied saying, "We are confident that by conducting such a rigorous analysis and developing highly restrictive provisions governing its use, there will be no risks of concern," and in October the EPA approved the use of methyl iodide as a soil fumigant in the U.S. It could not, however, yet be used in Washington and New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...

 due to lack of state approval. It also was not yet approved for use in California pending approval by the California growers Department of Pesticide Regulation. The California state agency often imposes tighter restrictions than the EPA, and the previous year its top officials had expressed concerns to the EPA about methyl iodide. "We are conducting our own risk assessment of methyl iodide, and we expect that process to continue for several months before we make a decision whether or how it can be used safely in California," said Glenn Brank, a spokesman for the state Department of Pesticide Regulation.

In February 2010, the California Department of Pesticide Regulation (DPR) concluded that methyl iodide is "highly toxic," and that "any anticipated scenario for the agricultural or structural fumigation use of this agent would result in exposures to a large number of the public and thus would have a significant adverse impact on the public health." It also concluded that adequate control of the chemical in these circumstances would be "difficult, if not impossible."

On December 1, 2010, methyl iodide use was approved as a pesticide in the State of California. Following the approval, a coalition of environmentalists, researchers and farmers—including California State Assemblyman Bill Monning
Bill Monning
William "Bill" Monning is an American educator, lawyer and politician. Monning was elected to the California State Assembly from the 27th Assembly District in the 2008 Assembly election....

, D-Carmel—gathered at locations in Santa Cruz County
Santa Cruz County, California
Santa Cruz County is a county located on the Pacific coast of the U.S. state of California, on the California Central Coast. The county forms the northern coast of the Monterey Bay. . As of the 2010 U.S. Census, its population was 262,382. The county seat is Santa Cruz...

 and six other sites around California to protest the impending use of methyl iodide and to ask governor-elect Jerry Brown
Jerry Brown
Edmund Gerald "Jerry" Brown, Jr. is an American politician. Brown served as the 34th Governor of California , and is currently serving as the 39th California Governor...

 to block it. Critics of methyl iodide cite both the cancer-causing aspects of the pesticide
Pesticide
Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...

 and the potential for it to leach out of fields, contaminating water supplies. Objections were also raised by two dozen California legislators and 54 scientists, including five Nobel laureates
Nobel Prize
The Nobel Prizes are annual international awards bestowed by Scandinavian committees in recognition of cultural and scientific advances. The will of the Swedish chemist Alfred Nobel, the inventor of dynamite, established the prizes in 1895...

.

On January 5, 2011, a coalition of farmworkers, community advocates and environmental health organizations sued to challenge California's approval of methyl iodide. The plaintiff groups are: Pesticide Action Network North America, United Farm Workers of America, Californians for Pesticide Reform, Pesticide Watch Education Fund, Worksafe, Communities and Children Advocates Against Pesticide Poisoning as well as farmworkers Jose Hidalgo Ramon and Zeferino Estrada. The suit challenges the state Department of Pesticide Regulation's December 20, 2010 approval of methyl iodide for use in California on the grounds that it violates the California Environmental Quality Act, the California Birth Defects Prevention Act, and the Pesticide Contamination Prevention Act. The suit also contends that the Department of Pesticide Regulation violated the law requiring involvement of the Office of Environmental Health Hazard Assessment in the development of farmworker safety regulations and made an unlawful finding of emergency with its request for Restricted Materials status for methyl iodide.

The first commercial applications of MIDAS soil fumigant in California began in Fresno County, in May, 2011. To date since its federal registration as a pesticide, more than 17,000 acres of soil used for growing crops have been treated in the United States without a single reported safety or health incident. Soils treated with methyl iodide are completely free of the compound before crops are planted, and to date neither the U.S. EPA nor the U.S. Food and Drug Administration (agencies that routinely conduct pesticide residue testing of fruit and produce) have found any detectable quantity of methyl iodide in the food supply from fruit and produce grown in methyl iodide-treated soils, nor have they detected any other soil fumigant product.

Toxicity and biological effects

According to the United States Department of Agriculture
United States Department of Agriculture
The United States Department of Agriculture is the United States federal executive department responsible for developing and executing U.S. federal government policy on farming, agriculture, and food...

 methyl iodide exhibits moderate to high
acute toxicity for inhalation and ingestion. The Centers for Disease Control and Prevention
Centers for Disease Control and Prevention
The Centers for Disease Control and Prevention are a United States federal agency under the Department of Health and Human Services headquartered in Druid Hills, unincorporated DeKalb County, Georgia, in Greater Atlanta...

 (CDC) lists inhalation, skin absorption, ingestion, and eye contact as possible exposure routes with target organs of the eyes, skin, respiratory system, and the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...

. Symptoms may include eye irritation, nausea, vomiting, dizziness, ataxia
Ataxia
Ataxia is a neurological sign and symptom that consists of gross lack of coordination of muscle movements. Ataxia is a non-specific clinical manifestation implying dysfunction of the parts of the nervous system that coordinate movement, such as the cerebellum...

, slurred speech, and dermatitis
Dermatitis
-Etymology:Dermatitis derives from Greek derma "skin" + -itis "inflammation" and genetic disorder.-Terminology:There are several different types of dermatitis. The different kinds usually have in common an allergic reaction to specific allergens. The term may describe eczema, which is also called...

.

Methyl iodide has an for oral administration to rats 76 mg/kg, and in the liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...

 it undergoes rapid conversion to S-methylglutathione
Glutathione
Glutathione is a tripeptide that contains an unusual peptide linkage between the amine group of cysteine and the carboxyl group of the glutamate side-chain...

.

In its risk assessment of methyl iodide, the U.S. EPA conducted an exhaustive scientific and medical literature search over the past 100 years for reported cases of human poisonings attributable to the compound. Citing the EPA as its source, the California Department of Pesticide Regulation concluded, “Over the past century, only 11 incidents of iodomethane poisoning have been reported in the published literature.” (Hermouet, C. et al 1996 & Appel, G.B. et al 1975) “An updated literature search on May 30, 2007 for iodomethane poisoning produced only one additional case report.” (Schwartz MD, et al 2005). All but one were industrial—not agricultural—accidents, and the remaining case of poisoning was an apparent suicide. Methyl iodide is routinely and regularly used in industrial processes as well as in most university and college chemistry departments for study and learning related to a variety of organic chemical reactions.

Carcinogenicity in mammals

Methyl iodide is listed under California Proposition 65 (1986)
California Proposition 65 (1986)
Proposition 65 is a California law passed by direct voter initiative in 1986 by a 63%-37% margin...

 as a chemical known by the state to cause cancer or reproductive toxicity based on evaluative studies performed in the 1970s.
It is considered a potential occupational carcinogen by the U.S. National Institute for Occupational Safety and Health
National Institute for Occupational Safety and Health
The National Institute for Occupational Safety and Health is the United States’ federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the Centers for Disease Control and Prevention within the U.S...

 (NIOSH), the U.S. Occupational Safety and Health Administration
Occupational Safety and Health Administration
The United States Occupational Safety and Health Administration is an agency of the United States Department of Labor. It was created by Congress of the United States under the Occupational Safety and Health Act, signed by President Richard M. Nixon, on December 29, 1970...

 and the U.S. Centers for Disease Control and Prevention
Centers for Disease Control and Prevention
The Centers for Disease Control and Prevention are a United States federal agency under the Department of Health and Human Services headquartered in Druid Hills, unincorporated DeKalb County, Georgia, in Greater Atlanta...

. The International Agency for Research on Cancer
International Agency for Research on Cancer
The International Agency for Research on Cancer is an intergovernmental agency forming part of the World Health Organisation of the United Nations....

 concluded based on studies performed after methyl iodide was Proposition 65 listed that: “Methyl iodide is not classifiable as to its carcinogenicity to humans (Group 3).” the Environmental Protection Agency classifies it as "not likely to be carcinogenic to humans in the absence of altered thyroid hormone homeostatis," i.e. it is a human carcinogen but only at doses large enough to disrupt thyroid function (via excess iodide). However this finding is disputed by the Pesticide Action Network
Pesticide Action Network
Pesticide Action Network is "an international coaltion of around 600 NGOs, citizens' groups, and individuals in about 60 countries."PAN is involved in fighting problems caused by pesticide use, and advocates ecologically sound alternatives. Branches include PAN North America, U...

 which states that the EPA’s cancer rating "appears to be based solely on a single rat inhalation study in which 66% of the control group and 54-62% of the rats in the other groups died before the end of
the study". They go on to state: "The EPA appears to be dismissing early peer-reviewed studies in favor of two nonpeer-reviewed studies conducted by the registrant that are flawed in design and execution." Despite requests by the U.S. EPA to the Pesticide Action Network
Pesticide Action Network
Pesticide Action Network is "an international coaltion of around 600 NGOs, citizens' groups, and individuals in about 60 countries."PAN is involved in fighting problems caused by pesticide use, and advocates ecologically sound alternatives. Branches include PAN North America, U...

to bring forth scientific evidence of their claims, they have not done so.

Additional sources

  • Sulikowski, G. A.; Sulikowski, M. M. (1999). in Coates, R.M.; Denmark, S. E. (Eds.) Handbook of Reagents for Organic Synthesis, Volume 1: Reagents, Auxiliaries and Catalysts for C-C Bond Formation New York: Wiley, pp. 423–26.


External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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